10-Q

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM 10-Q

☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended March 31, 2025

☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from _____ to _____

		I.R.S. Employer
Commission File Number	Exact name of registrant as specified in its charter	Identification Number
001-3375	DOMINION ENERGY SOUTH CAROLINA, INC.	57-0248695
	south carolina
	(State or other jurisdiction of incorporation or organization)
	220 OPERATION WAY
	CAYCE, South Carolina	29033
	(Address of principal executive offices)	(Zip Code)
	(804) 819-2284
	(Registrants’ telephone number)

Securities registered pursuant to Section 12(b) of the Act:

None

Indicate by check mark whether the registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No ☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ☒ No ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “non-accelerated filer,” “smaller reporting company” and "emerging growth company" in Rule 12b-2 of the Exchange Act.

Large accelerated filer	☐	Accelerated filer	☐	Emerging growth company	☐
Non-accelerated filer	☒	Smaller reporting company	☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐ No ☒

Indicate the number of shares outstanding of each of the issuer’s classes of common stock, as of the latest practicable date. At April 25, 2025, Dominion Energy South Carolina, Inc. had outstanding 40,296,147 shares of common stock, all of which were held by SCANA Corporation, a wholly-owned subsidiary of Dominion Energy, Inc.

Dominion Energy South Carolina, Inc. meets the conditions set forth in General Instruction H(1)(a) and (b) of Form 10-Q and is filing this Form 10-Q under the reduced disclosure format.

1
 

TABLE OF CONTENTS

		Page
	Glossary of Terms	3
PART I. FINANCIAL INFORMATION
Item 1.	Financial Statements	5
Item 2.	Management’s Discussion and Analysis of Financial Condition and Results of Operations	26
Item 4.	Controls and Procedures	29
PART II. OTHER INFORMATION
Item 1.	Legal Proceedings	30
Item 1A.	Risk Factors	30
Item 5.	Other Information	30
Item 6.	Exhibits	31

2

GLOSSARY OF TERMS

The following abbreviations or acronyms used in this Form 10-Q are defined below:

Abbreviation or Acronym	Definition
2017 Tax Reform Act	An Act to Provide for Reconciliation Pursuant to Titles II and V of the Concurrent Resolution on the Budget for Fiscal Year 2018 (previously known as The Tax Cuts and Jobs Act) enacted on December 22, 2017
AFUDC	Allowance for funds used during construction
AOCI	Accumulated other comprehensive income (loss)
ARO	Asset retirement obligation
bcf	Billion cubic feet
BTA	Best technology available
CAA	Clean Air Act
CCR	Coal combustion residual
CEO	Chief Executive Officer
CERCLA	Comprehensive Environmental Response, Compensation and Liability Act of 1980, also known as Superfund
CFO	Chief Financial Officer
CO2	Carbon dioxide
Cooling degree days	Units measuring the extent to which the average daily temperature is greater than 75 degrees Fahrenheit, calculated as the difference between 75 degrees and the average temperature for that day
CODM	Chief Operating Decision Maker
CPCN	Certificate of Public Convenience and Necessity
CUA	Capacity Use Area
CWA	Clean Water Act
DES	Dominion Energy Services, Inc.
DESC	The legal entity, Dominion Energy South Carolina, Inc., one or more of its consolidated entities or operating segment, or the entirety of Dominion Energy South Carolina, Inc. and its consolidated entities
Dominion Energy	The legal entity, Dominion Energy, Inc., one or more of its consolidated subsidiaries (other than DESC) or operating segments, or the entirety of Dominion Energy, Inc. and its consolidated subsidiaries
Dominion Energy South Carolina	Dominion Energy South Carolina operating segment
DSM	Demand-side management
Dth	Dekatherm
ELG Rule	Effluent limitations guidelines for the steam electric power generating category
EPA	U.S. Environmental Protection Agency
FERC	Federal Energy Regulatory Commission
Fuel Company	South Carolina Fuel Company, Inc.
GAAP	U.S. generally accepted accounting principles
GENCO	South Carolina Generating Company, Inc.
GHG	Greenhouse gas
Heating degree days	Units measuring the extent to which the average daily temperature is less than 60 degrees Fahrenheit, calculated as the difference between 60 degrees and the average temperature for that day
kV	Kilovolt
MD&A	Management’s Discussion and Analysis of Financial Condition and Results of Operations
MGD	Million gallons per day
MWh	Megawatt hour
Natural Gas Rate Stabilization Act	Legislation effective February 2005 designed to improve and maintain natural gas service infrastructure to meet the needs of customers in South Carolina

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Abbreviation or Acronym	Definition
NND Project	V. C. Summer Units 2 and 3 nuclear development project under which DESC and Santee Cooper undertook to construct two Westinghouse AP1000 Advanced Passive Safety nuclear units in Jenkinsville, South Carolina
NOx	Nitrogen oxide
Order 1000	Order issued by FERC adopting requirements for electric transmission planning, cost allocation and development
PSD	Prevention of significant deterioration
Santee Cooper	South Carolina Public Service Authority
SCANA	The legal entity, SCANA Corporation, one or more of its consolidated subsidiaries (other than DESC) or the entirety of SCANA Corporation and its consolidated subsidiaries
SCANA Combination	Dominion Energy’s acquisition of SCANA completed on January 1, 2019 pursuant to the terms of the SCANA Merger Agreement
SCANA Merger Agreement	Agreement and plan of merger entered on January 2, 2018 between Dominion Energy and SCANA
SCANA Merger Approval Order	Final order issued by the South Carolina Commission on December 21, 2018 setting forth its approval of the SCANA Combination
SCDES	South Carolina Department of Environmental Services
SEC	U.S. Securities and Exchange Commission
SO2	Sulfur dioxide
South Carolina Commission	Public Service Commission of South Carolina
Summer	V. C. Summer nuclear power station
Toshiba	Toshiba Corporation, parent company of Westinghouse
Toshiba Settlement	Settlement Agreement dated as of July 27, 2017, by and among Toshiba, DESC and Santee Cooper
VIE	Variable interest entity
Virginia Power	The legal entity, Virginia Electric and Power Company, a wholly-owned subsidiary of Dominion Energy, one or more of its consolidated subsidiaries or operating segment, or the entirety of Virginia Electric and Power Company and its consolidated subsidiaries
Westinghouse	Westinghouse Electric Company LLC

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PART I. FINANCIAL INFORMATION

ITEM 1. FINANCIAL STATEMENTS

Dominion Energy South Carolina, Inc.

Consolidated Balance Sheets

(Unaudited)

(millions)	March 31, 2025			December 31, 2024
ASSETS
Utility plant in service	$	16,488		$	16,300
Accumulated depreciation and amortization		(5,809	)		(5,761	)
Construction work in progress		913			899
Nuclear fuel, net of accumulated amortization		215			224
Utility plant, net ($822 and $824 related to VIEs)		11,807			11,662
Nonutility Property and Investments:
Nonutility property, net of accumulated depreciation		16			16
Assets held in trust, nuclear decommissioning		269			268
Nonutility property and investments, net		285			284
Current Assets:
Cash and cash equivalents		7			—
Receivables:
Customer, net of allowance for uncollectible accounts of $8 and $6		403			423
Affiliated and related party		3			4
Other		87			104
Inventories (at average cost):
Fuel		88			83
Gas storage		19			22
Materials and supplies		214			211
Prepayments		81			91
Derivative assets(1)		73			63
Regulatory assets		340			299
Other current assets		15			16
Total current assets ($83 and $79 related to VIEs)		1,330			1,316
Deferred Debits and Other Assets:
Derivative assets(1)		206			309
Regulatory assets		3,362			3,342
Affiliated receivables		26			26
Other		102			102
Total deferred debits and other assets ($27 and $25 related to VIEs)		3,696			3,779
Total assets	$	17,118		$	17,041

(1) See Note 12 for amounts attributable to affiliates.

See Notes to Consolidated Financial Statements.

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Dominion Energy South Carolina, Inc.

Consolidated Balance Sheets—(Continued)

(Unaudited)

(millions)	March 31, 2025			December 31, 2024
CAPITALIZATION AND LIABILITIES
Common Stock - no par value, 40.3 million shares outstanding	$	4,338		$	4,088
Retained earnings		831			689
Accumulated other comprehensive loss		(1	)		(1	)
Total common equity		5,168			4,776
Noncontrolling interest		214			206
Total equity		5,382			4,982
Long-term debt, net		4,666			4,220
Affiliated long-term debt		230			230
Finance leases		2			2
Total long-term debt		4,898			4,452
Total capitalization		10,280			9,434
Current Liabilities:
Short-term borrowings		210			250
Securities due within one year		2			2
Accounts payable		201			273
Affiliated and related party payables		623			995
Customer deposits and customer prepayments		75			82
Taxes accrued		73			254
Interest accrued		90			83
Regulatory liabilities		227			201
Derivative liabilities		1			—
Other		159			201
Total current liabilities		1,661			2,341
Deferred Credits and Other Liabilities:
Deferred income taxes and investment tax credits		1,447			1,409
Asset retirement obligations		1,142			1,139
Pension and other postretirement benefits		109			109
Derivative liabilities		6			1
Regulatory liabilities		2,361			2,488
Other		112			120
Total deferred credits and other liabilities		5,177			5,266
Commitments and Contingencies (see Note 10)
Total capitalization and liabilities	$	17,118		$	17,041

See Notes to Consolidated Financial Statements.

6

Dominion Energy South Carolina, Inc.

Consolidated Statements of Comprehensive Income

(Unaudited)

	Three Months Ended March 31,
(millions)	2025		2024
Operating Revenue(1)	$	986	$	775
Operating Expenses:
Fuel used in electric generation		204		145
Purchased power(1)		22		10
Gas purchased for resale		126		79
Other operations and maintenance		131		122
Other operations and maintenance – affiliated suppliers		43		41
Depreciation and amortization		140		136
Other taxes(1)		82		78
Total operating expenses		748		611
Operating income		238		164
Other income (expense), net		3		1
Interest charges, net of AFUDC of $6 and $4(1)		71		67
Income before income tax expense		170		98
Income tax expense		20		18
Net Income and Other Comprehensive Income		150		80
Comprehensive Income Attributable to Noncontrolling Interest		8		6
Comprehensive Income Available to Common Shareholder	$	142	$	74

(1) See Note 12 for amounts attributable to affiliates.

See Notes to Consolidated Financial Statements.

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Dominion Energy South Carolina, Inc.

Consolidated Statements of Cash Flows

(Unaudited)

	Three Months Ended March 31,
(millions)	2025			2024
Operating Activities
Net income	$	150		$	80
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred income taxes, net		38			5
Depreciation and amortization		140			136
Amortization of nuclear fuel		10			9
Other adjustments		5			—
Changes in certain assets and liabilities:
Receivables		29			45
Receivables - affiliated and related party		1			1
Inventories		(4	)		(1	)
Prepayments and deposits, net		3			2
Regulatory assets		(98	)		79
Regulatory liabilities		(100	)		41
Accounts payable		(34	)		(18	)
Accounts payable - affiliated and related party		12			43
Taxes accrued		(181	)		(177	)
Interest accrued		7			2
Net realized and unrealized changes related to commodity derivative activities		98			(78	)
Pension and other postretirement benefits		—			(1	)
Other assets and liabilities		(22	)		(2	)
Net cash provided by operating activities		54			166
Investing Activities
Property additions and construction expenditures		(297	)		(268	)
Proceeds from investments and sales or disposals of assets, including asset retirement costs		(23	)		(13	)
Purchase of investments		—			(5	)
Other		1			—
Net cash used in investing activities		(319	)		(286	)
Financing Activities
Proceeds from issuance of debt		450			—
Dividend to parent		—			(62	)
Contribution from parent		250			—
Short-term borrowings, net		(40	)		(44	)
Short-term borrowings - affiliated, net		(384	)		230
Other		(4	)		(1	)
Net cash provided by financing activities		272			123
Net increase in cash, restricted cash and equivalents		7			3
Cash, restricted cash and equivalents at beginning of period(1)		—			1
Cash, restricted cash and equivalents at end of period(1)	$	7		$	4
Supplemental Cash Flow Information
Significant noncash investing and financing activities:
Accrued construction expenditures	$	73		$	56
Operating leases(2)		4			—

(1)At March 31, 2025, December 31, 2024, March 31, 2024 and December 31, 2023 there were no restricted cash and equivalents balances.

(2)Finance leases entered into, if any, were inconsequential for all periods presented.

See Notes to Consolidated Financial Statements.

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Dominion Energy South Carolina, Inc.

Consolidated Statements of Changes in Common Equity

(Unaudited)

	Common Stock
(millions)	Shares		Amount		Retained Earnings			AOCI			Noncontrolling Interest		Total Equity
December 31, 2023		40	$	4,088	$	592		$	(1	)	$	183	$	4,862
Total comprehensive income available to    common shareholder						74						6		80
Dividend to parent						(62	)							(62	)
March 31, 2024		40	$	4,088	$	604		$	(1	)	$	189	$	4,880
December 31, 2024		40	$	4,088	$	689		$	(1	)	$	206	$	4,982
Total comprehensive income available to    common shareholder						142						8		150
Capital contribution from parent			250											250
March 31, 2025		40	$	4,338	$	831		$	(1	)	$	214	$	5,382

See Notes to Consolidated Financial Statements.

9

Dominion Energy South Carolina, Inc.

Notes to Consolidated Financial Statements

(Unaudited)

The following notes should be read in conjunction with the Notes to Consolidated Financial Statements appearing in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024.

These are interim financial statements and, due to the seasonality of DESC’s business and matters that may occur during the rest of the year, the amounts reported in the Consolidated Statements of Comprehensive Income are not necessarily indicative of amounts expected for the full year. In the opinion of management, the information furnished herein reflects all adjustments which are necessary for a fair statement of the results for the interim periods reported, and such adjustments are of a normal recurring nature unless otherwise noted. In addition, the preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amount of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Certain amounts in DESC’s 2024 Consolidated Financial Statements and Notes have been reclassified to conform to the 2025 presentation for comparative purposes; however, such reclassifications did not affect DESC’s net income and other comprehensive income, total assets, liabilities, equity or cash flows.

DESC is a wholly-owned subsidiary of SCANA, which is a wholly-owned subsidiary of Dominion Energy.

1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Basis of Consolidation and Variable Interest Entities

DESC has determined that it has a controlling financial interest in each of GENCO and Fuel Company (which are considered to be VIEs) and, accordingly, DESC’s Consolidated Financial Statements include, after eliminating intercompany balances and transactions, the accounts of DESC, GENCO and Fuel Company. See Note 2 to the Consolidated Financial Statements included in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024 for a description of GENCO and Fuel Company.

DESC purchases shared services from DES, an affiliated VIE that provides accounting, legal, finance and certain administrative and technical services to all Dominion Energy subsidiaries, including DESC. DESC has determined that it is not the primary beneficiary of DES as it does not have either the power to direct the activities that most significantly impact its economic performance or an obligation to absorb losses and benefits which could be significant to it. See Note 12 for amounts attributable to affiliates.

Significant Accounting Policies

There have been no significant changes from Note 2 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024.

2. RATE AND OTHER REGULATORY MATTERS

Regulatory Matters Involving Potential Loss Contingencies

As a result of issues generated in the ordinary course of business, DESC is involved in various regulatory matters. Certain regulatory matters may ultimately result in a loss; however, as such matters are in an initial procedural phase, involve uncertainty as to the outcome of pending reviews or orders, and/or involve significant factual issues that need to be resolved, it is not possible for DESC to estimate a range of possible loss. For regulatory matters that DESC cannot estimate, a statement to this effect is made in the description of the matter. Other matters may have progressed sufficiently through the regulatory process such that DESC is able to estimate a range of possible loss. For regulatory matters that DESC is able to reasonably estimate a range of possible losses, an estimated range of possible loss is provided, in excess of the accrued liability (if any) for such matters. Any estimated range is based on currently available information, involves elements of judgment and significant uncertainties and may not represent DESC’s maximum possible loss exposure. The circumstances of such regulatory matters will change from time to time and actual results may vary significantly from the current estimate. For current matters not specifically reported below, management does not anticipate that the outcome from such matters would have a material effect on DESC’s financial position, liquidity or results of operations.

Other Regulatory Matters

Other than the following matters, there have been no significant developments regarding the pending regulatory matters disclosed in Note 3 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024.

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Electric – Cost of Fuel

DESC’s retail electric rates include a cost of fuel component approved by the South Carolina Commission which may be adjusted periodically to reflect changes in the price of fuel purchased by DESC. In February 2025, DESC filed with the South Carolina Commission a proposal to increase the total fuel cost component of retail electric rates. DESC’s proposed adjustment is designed to recover DESC’s current base fuel costs, including its existing under-collected balance, over the 12-month period beginning with the first billing cycle of May 2025. In addition, DESC proposed an increase to its variable environmental and avoided capacity cost component. The net effect is a proposed annual increase of $154 million. In March 2025, DESC and the South Carolina Office of Regulatory Staff filed a settlement agreement with the South Carolina Commission for approval to make certain adjustments to the February 2025 filing that would result in an inconsequential change to the proposed annual increase. In April 2025, the South Carolina Commission approved the settlement agreement, with rates effective with the first billing cycle of May 2025.

Electric - Transmission Project

In December 2024, DESC filed an application with the South Carolina Commission requesting approval of a CPCN to construct and operate the Ritter - Yemassee Transmission Line #2, comprised of a 17-mile 230 kV transmission line and associated facilities in Colleton and Hampton Counties, South Carolina with an estimated total project cost of $55 million. In April 2025, the South Carolina Commission approved the application.

Electric – Other

DESC has approval for a DSM rider through which it recovers expenditures related to its DSM programs. In January 2025, DESC filed an application with the South Carolina Commission seeking approval to recover $46 million of costs and net lost revenues associated with these programs, along with an incentive to invest in such programs. DESC requested that rates be effective with the first billing cycle of May 2025. In April 2025, the South Carolina Commission approved the request, effective with the first billing cycle of May 2025.

DESC utilizes a pension costs rider approved by the South Carolina Commission which is designed to allow recovery of projected pension costs, including under-collected balances or net of over-collected balances, as applicable. The rider is typically reviewed for adjustment every 12 months with any resulting increase or decrease going into effect beginning with the first billing cycle in May. In February 2025, DESC requested that the South Carolina Commission approve an adjustment to this rider to decrease annual revenue by $13 million. In April 2025, the South Carolina Commission approved the request.

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Regulatory Assets and Regulatory Liabilities

Rate-regulated utilities recognize in their financial statements certain revenues and expenses in different periods than do other enterprises. As a result, DESC has recorded regulatory assets and regulatory liabilities which are summarized in the following table. Except for NND Project costs and certain other unrecovered costs referenced herein, substantially all regulatory assets are either explicitly excluded from rate base or are effectively excluded from rate base due to their being offset by related liabilities.

	March 31,		December 31,
(millions)	2025		2024
Regulatory assets:
NND Project costs(1)	$	138	$	138
AROs(2)		6		8
Deferred employee benefit plan costs(3)		5		8
Other unrecovered plant(4)		18		18
DSM programs(5)		23		24
Cost of fuel and purchased gas under-collections(6)		92		35
Other		58		68
Regulatory assets - current		340		299
NND Project costs(1)		1,776		1,811
AROs(2)		704		695
Deferred employee benefit plan costs(3)		96		94
Interest rate hedges(7)		167		167
Other unrecovered plant(4)		94		89
DSM programs(5)		48		49
Environmental remediation costs(8)		42		42
Deferred storm damage costs(9)		77		76
Deferred transmission operating costs(10)		71		72
Derivatives(11)		94		95
Other(12)		193		152
Regulatory assets - noncurrent		3,362		3,342
Total regulatory assets	$	3,702	$	3,641
Regulatory liabilities:
Monetization of guaranty settlement(13)	$	67	$	67
Income taxes refundable through future rates(14)		17		24
Reserve for refunds to electric utility customers(15)		67		73
Derivatives(11)		44		27
Other		32		10
Regulatory liabilities - current		227		201
Monetization of guaranty settlement(13)		552		568
Income taxes refundable through future rates(14)		838		820
Asset removal costs(16)		597		598
Reserve for refunds to electric utility customers(15)		146		161
Derivatives(11)		223		328
Other		5		13
Regulatory liabilities - noncurrent		2,361		2,488
Total regulatory liabilities	$	2,588	$	2,689

(1)Reflects expenditures associated with the NND Project, which pursuant to the SCANA Merger Approval Order, will be recovered from electric service customers over a 20-year period ending in 2039.

(2)Represents uncollected costs, including deferred depreciation and accretion expense, related to legal obligations associated with the future retirement of generation, transmission and distribution properties. The AROs primarily relate to DESC’s electric generating facilities, including Summer, and are expected to be recovered over the related property lives and periods of decommissioning which may range up to approximately 105 years. In addition, the balance reflects amounts related to the EPA’s May 2024 final rule concerning CCR as discussed in Note 10.

(3)Employee benefit plan costs have historically been recovered as they have been recorded under GAAP. Deferred employee benefit plan costs represent amounts of pension and other postretirement benefit costs which were accrued as liabilities and treated as regulatory assets pursuant to FERC guidance, and costs deferred pursuant to specific South Carolina Commission regulatory orders. Based on rates currently in effect, DESC expects to recover certain deferred benefit costs through utility rates over average service periods of participating employees, which is approximately 11 years. DESC expects to recover other deferred pension costs through utility rates over periods through 2044.

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(4)Represents the carrying value of coal-fired generating units, including related materials and supplies inventory, retired from service prior to being fully depreciated. DESC is amortizing these amounts through cost of service rates following depreciation amounts that were designed to recover the retired units cost over their previous estimated remaining useful lives, which has been estimated to be through 2025. Based on current projections of remaining decommissioning costs, projected recovery is expected to extend through 2039. In addition, amounts include unrecovered costs of existing meters and equipment retired from service prior to being fully depreciated as part of the Advanced Metering Infrastructure project, which are being recovered through rates through 2028. This amount also includes certain inventory and preliminary survey and investigation charges being amortized through 2026 related to the transition or conversion from coal to gas fired generation at certain facilities. The majority of unamortized amounts are included in rate base and are earning a current return.

(5)Primarily represents deferred costs associated with electric demand reduction programs, and such deferred costs are currently being recovered over three years through an approved rate rider.

(6)Represents amounts under- or over-collected from customers pursuant to the cost of fuel and purchased gas components approved by the South Carolina Commission.

(7)Represents settled interest rate derivatives designated as cash flow hedges expected to be amortized to interest expense over the lives of the underlying debt through 2065.

(8)Reflects amounts associated with the assessment and clean-up of sites currently or formerly owned by DESC. Such remediation costs are expected to be recovered over periods of up to 24 years. See Note 10 for additional information.

(9)Represents storm restoration costs for which DESC expects to receive future recovery. Pursuant to the settlement agreement approved in DESC’s retail electric base rate case in August 2024, for costs incurred prior to September 2024, DESC expects to receive future recovery through customer rates through 2034 and for costs incurred effective September 2024, DESC expects to receive future recovery through customer rates of approximately $2 million each year. Unamortized amounts are included in rate base and are earning a current return.

(10)Includes deferred depreciation and property taxes associated with certain transmission assets for which DESC expects future recovery from customers through 2062. Unamortized amounts are included in rate base and earning a current return.

(11)Represents changes in the fair value of derivatives, excluding separately presented interest rate hedges, that following settlement are expected to be recovered from or refunded to customers.

(12)Various other regulatory assets are expected to be recovered through rates over varying periods through 2078.

(13)Represents proceeds related to the monetization of the Toshiba Settlement. In accordance with the SCANA Merger Approval Order, this balance, net of amounts that may be required to satisfy liens, will be refunded to electric customers over a 20-year period ending in 2039.

(14)Includes (i) excess deferred income taxes arising from the remeasurement of deferred income taxes in connection with the enactment of the 2017 Tax Reform Act (certain of which are protected under normalization rules and will be amortized over the remaining lives of related property, and certain of which will be amortized to the benefit of customers over prescribed periods as instructed by regulators) and (ii) deferred income taxes arising from investment tax credits, offset by (iii) deferred income taxes that arise from utility operations that have not been included in customer rates (a portion of which relate to depreciation and are expected to be recovered over the remaining lives of the related property which may range up to 85 years).

(15)Reflects amounts previously collected from retail electric customers of DESC for the NND Project to be credited to customers over an estimated 11-year period effective February 2019 in connection with the SCANA Merger Approval Order.

(16)Represents estimated net collections through depreciation rates of amounts to be expended for the removal of assets in the future.

Regulatory assets have been recorded based on the probability of their recovery. All regulatory assets represent incurred costs that may be deferred under GAAP for regulated operations. The South Carolina Commission or FERC has reviewed and approved through specific orders certain of the items shown as regulatory assets. In addition, regulatory assets include, but are not limited to, certain costs which have not been specifically approved for recovery by one of these regulatory agencies. While such costs are not currently being recovered, management believes that they would be allowable under existing rate-making concepts embodied in rate orders or applicable state law and expects to recover these costs through rates in future periods.

3. OPERATING REVENUE

DESC’s revenue consists of the following:

Three Months Ended March 31,	2025				2024
(millions)	Electric		Gas		Electric		Gas
Customer class:
Residential	$	371	$	151	$	283	$	117
Commercial		228		54		188		41
Industrial		109		27		87		18
Other		32		8		28		6
Revenues from contracts with customers		740		240		586		182
Other revenues		6		—		7		—
Total Operating Revenues	$	746	$	240	$	593	$	182

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Contract liabilities represent the obligation to transfer goods or services to a customer for which consideration has already been received from the customer. DESC had contract liability balances of $5 million and $6 million at March 31, 2025 and December 31, 2024, respectively. During both the three months ended March 31, 2025 and 2024, DESC recognized revenue of $3 million from the beginning contract liability balances as DESC fulfilled its obligations to provide service to its customers. Contract liabilities are recorded in customer deposits and customer prepayments in the Consolidated Balance Sheets.

Balances and activity related to contract costs deferred as regulatory assets were as follows:

	Regulatory Assets
(millions)	March 31, 2025		December 31, 2024
Beginning balance	$	10	$	11
Additional costs		4		—
Amortization		—		(1	)
Ending balance	$	14	$	10

4. EQUITY

For all periods presented, DESC’s authorized shares of common stock, no par value, were 50 million, of which 40.3 million were issued and outstanding, and DESC’s authorized shares of preferred stock, no par value, were 20 million, of which 1,000 shares were issued and outstanding. All outstanding shares of common and preferred stock are held by SCANA.

There have been no material changes to the dividend restrictions affecting DESC described in Note 5 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024.

During the first quarter of 2025, DESC received equity contributions of $250 million from Dominion Energy. DESC primarily used these funds for working capital needs including reducing short-term debt.

5. LONG-TERM AND SHORT-TERM DEBT

DESC’s short-term financing is supported through its access as co-borrower to Dominion Energy’s $7.0 billion joint revolving credit facility, as amended April 2025. The credit facility can be used for working capital, as support for the combined commercial paper programs of the borrowers under the credit facility and for other general corporate purposes. Other than the items discussed below, there have been no significant changes from Note 6 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024.

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At March 31, 2025, DESC’s share of commercial paper and letters of credit outstanding under its joint credit facility with Dominion Energy was as follows:

(millions)	Maximum Facility Sub-Limit		Outstanding Commercial Paper		Outstanding Letters of Credit
Joint revolving credit facility(1)	$	1,000	$	210	$	—

(1)A maximum of $1.0 billion of the facility is available to DESC, assuming adequate capacity is available after giving effect to uses by co-borrowers Dominion Energy and Virginia Power. A sub-limit for DESC is set within the facility limit but can be changed at the option of the co-borrowers multiple times per year. At March 31, 2025, the sub-limit for DESC was $500 million. In April 2025, the sub-limit was increased up to $1.0 billion. If DESC has liquidity needs in excess of its sub-limit, the sub-limit may be changed provided that it does not exceed $1.0 billion or such needs may be satisfied through short-term borrowings from Dominion Energy. This credit facility, as amended in April 2025, matures in April 2030, with the potential to be extended by the borrowers to April 2032. The credit facility can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $3.0 billion (or the sub-limit, whichever is less) of letters of credit.

In March 2025, FERC granted DESC authority through March 2027 to issue short-term indebtedness (pursuant to Section 204 of the Federal Power Act) in amounts not to exceed $1.8 billion outstanding with maturity dates of one year or less. At March 31, 2025, DESC had issued $210 million in commercial paper supported by its joint revolving credit facility with Dominion Energy as disclosed above and had drawn on $227 million of its intercompany credit facility with Dominion Energy, as permitted by this FERC authorization. In addition, in March 2025, FERC granted GENCO authority through March 2027 to issue short-term indebtedness not to exceed $300 million outstanding with maturity dates of one year or less. At March 31, 2025, GENCO had drawn on $63 million of its intercompany credit facility with Dominion Energy, as permitted by this FERC authorization.

DESC is obligated with respect to an aggregate of $68 million of industrial revenue bonds which are secured by letters of credit. These letters of credit expire, subject to renewal, in the fourth quarter of 2025.

DESC, GENCO and Fuel Company each have intercompany credit facilities with Dominion Energy with a maximum capacity of $900 million, $200 million and $400 million, respectively. At March 31, 2025 and December 31, 2024, DESC, GENCO and Fuel Company collectively had borrowings outstanding under these agreements totaling $558 million and $942 million, respectively, which are recorded in affiliated and related party payables in DESC’s Consolidated Balance Sheets. Interest charges associated with these agreements were $11 million and $10 million for the three months ended March 31, 2025 and 2024, respectively.

In January 2025, DESC issued $450 million of 5.30% first mortgage bonds that mature in 2035. The proceeds were used for general corporate purposes and/or to repay short-term debt.

6. INCOME TAXES

For continuing operations, including noncontrolling interests, the statutory U.S. federal income tax rate reconciles to DESC’s effective income tax rate as follows:

Three Months Ended March 31,	2025			2024
U.S. statutory rate		21.0	%		21.0	%
Increases (reductions) resulting from:
State taxes, net of federal benefit		10.8			3.9
Reversal of excess deferred income taxes		(2.4	)		(5.3	)
Allowance for equity funds used during construction		—			(0.7	)
Remeasurements and settlements of uncertain tax positions		(17.5	)	—
Other, net		(0.2	)	—
Effective tax rate		11.7	%		18.9	%

As of March 31, 2025, DESC’s effective tax rate reflects an income tax net benefit of $18 million reflecting a $30 million remeasurement of an unrecognized tax benefit partially deferred to regulatory liabilities. See Note 7 to the Consolidated Financial Statements in DESC's Annual Report on Form 10-K for the year ended December 31, 2024, for a discussion of these unrecognized tax benefits.

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7. DERIVATIVE FINANCIAL INSTRUMENTS

DESC’s accounting policies, objectives, and strategies for using derivative instruments are discussed in Note 2 in the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024. See Note 8 for further information about fair value measurements and associated valuation methods for derivatives.

Cash collateral, as presented in the table below, is used to offset derivative assets and liabilities when applicable. Certain of DESC’s derivative instruments contain credit-related contingent provisions. These provisions require DESC to provide collateral upon the occurrence of specific events, primarily a credit rating downgrade. If the credit-related contingent features underlying the instruments that are in a liability position and not fully collateralized with cash were fully triggered as of March 31, 2025 and December 31, 2024, DESC would have been required to post $2 million and $1 million, respectively, of additional collateral to its counterparties. The collateral that would be required to be posted includes the impacts of any offsetting asset positions and any amounts already posted for derivatives and non-derivative contracts per contractual terms. DESC had not posted any collateral at March 31, 2025 and December 31, 2024 related to derivatives with credit-related contingent provisions that are in a liability position and not fully collateralized with cash. The aggregate fair value of all derivative instruments with credit-related contingent provisions that are in a liability position and not fully collateralized with cash as of March 31, 2025 and December 31, 2024 was $2 million and $1 million, respectively, which does not include the impact of any offsetting asset positions.

The table below presents derivative balances by type of financial instrument, if the gross amounts recognized in the Consolidated Balance Sheets were netted with derivative instruments and cash collateral received or paid:

	March 31, 2025								December 31, 2024
	Gross Amounts Not Offset in the Consolidated Balance Sheet								Gross Amounts Not Offset in the Consolidated Balance Sheet
(millions)	Gross Assets Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Received		Net Amounts		Gross Assets Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Received		Net Amounts
Interest rate contracts:
Over-the-counter	$	2	$	—	$	—	$	2	$	2	$	—	$	—	$	2
Commodity contracts:
Over-the-counter	$	78	$	—	$	—	$	78	$	81	$	—	$	—	$	81
Total derivatives	$	80	$	—	$	—	$	80	$	83	$	—	$	—	$	83

(1)Excludes derivative assets of $199 million and $289 million at March 31, 2025 and December 31, 2024, respectively, which are not subject to master netting or similar arrangements.

	March 31, 2025								December 31, 2024
	Gross Amounts Not Offset in the Consolidated Balance Sheet								Gross Amounts Not Offset in the Consolidated Balance Sheet
(millions)	Gross Liabilities Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Paid		Net Amounts		Gross Liabilities Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Paid		Net Amounts
Interest rate contracts:
Over-the-counter	$	2	$	—	$	—	$	2	$	1	$	—	$	—	$	1
Total derivatives	$	2	$	—	$	—	$	2	$	1	$	—	$	—	$	1

(1)Excludes derivative liabilities of $5 million at March 31, 2025, which are not subject to master netting or similar arrangements. DESC did not have any derivative liabilities at December 31, 2024 which were not subject to master netting or similar arrangements.

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Volumes

The following table presents the volume of derivative activity at March 31, 2025. These volumes are based on open derivative positions and represent the combined absolute value of their long and short positions.

Natural Gas (bcf):	Current		Noncurrent
Basis(1)		41		31
Electricity (MWh in millions):
Fixed price		2		22
Interest rate(2) (in millions)		—		71

(1)Includes options.

(2)Maturity is determined based on final settlement period.

Fair Value and Gains and Losses on Derivative Instruments

The following tables present the fair values of derivatives and where they are presented in the Consolidated Balance Sheets:

	Assets		Liabilities
(millions)
At March 31, 2025
Current derivatives not under cash flow hedge accounting
Commodity	$	73	$	—
Interest rate		—		1
Total current derivatives	$	73	$	1
Noncurrent derivatives not under cash flow hedge accounting
Commodity	$	204	$	5
Interest rate		2		1
Total noncurrent derivatives		206		6
Total derivatives	$	279	$	7
At December 31, 2024
Current derivatives not under cash flow hedge accounting
Commodity	$	63	$	—
Total current derivatives	$	63	$	—
Noncurrent derivatives not under cash flow hedge accounting
Commodity	$	307	$	—
Interest rate		2		1
Total noncurrent derivatives		309		1
Total derivatives	$	372	$	1

The following tables present the gains and losses on derivatives, as well as where the associated activity is presented in the Consolidated Balance Sheets and Statements of Comprehensive Income:

Derivatives in Cash Flow Hedging Relationships

(millions)	Increase (Decrease) in Derivatives Subject to Regulatory Treatment(1)(2)
Three Months Ended March 31,	2025		2024
Derivative type and location of gains (losses):
Interest rate	$	—	$	—
Total	$	—	$	—

(1)Represents net derivative activity deferred into and amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/ liabilities have no associated effect in the Consolidated Statements of Comprehensive Income.

(2)All derivatives in cash flow hedging relationships have settled and are being amortized over the life of the debt.

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Derivatives Not Designated as Hedging Instruments

(millions)	Amount of Gain (Loss) Recognized in Income on Derivatives(1)
Three Months Ended March 31,	2025			2024
Derivative type and location of gains (losses):
Commodity:
Purchased power	$	3		$	(2	)
Interest rate:
Interest charges		(1	)		(1	)
Total	$	2		$	(3	)

(1)Includes derivative activity amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/liabilities have no associated effect in the Consolidated Statements of Comprehensive Income.

8. FAIR VALUE MEASUREMENTS, INCLUDING DERIVATIVES

DESC’s fair value measurements are made in accordance with the policies discussed in Note 2 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024. See Note 7 in this report for further information about DESC’s derivatives and hedge accounting activities.

The following table presents DESC’s quantitative information about Level 3 fair value measurements at March 31, 2025. The range and weighted-average are presented in dollars for market price inputs and percentages for price volatility.

	Fair Value (millions)		Valuation Techniques	Unobservable Input		Range	Weighted-average(1)
Assets
Physical forwards:
Electricity	$	199	Discounted cash flow	Market price (per MWh)	(3)	30-83	48
Physical options:
Natural gas(2)		76	Option model	Market price (per Dth)	(3)	3-8	4
				Price volatility	(4)	11%-74%	44%
Total assets	$	275
Liabilities
Physical forwards:
Electricity	$	5	Discounted cash flow	Market price (per MWh)	(3)	30-81	50
Total liabilities	$	5

(1)Averages weighted by volume.

(2)Includes basis.

(3)Represents market prices beyond defined terms for Levels 1 and 2.

(4)Represents volatilities unrepresented in published markets.

Sensitivity of the fair value measurements to changes in the significant unobservable inputs is as follows:

Significant Unobservable Inputs	Position	Change to Input	Impact on Fair Value Measurement
Market price	Buy	Increase (decrease)	Gain (loss)
Market price	Sell	Increase (decrease)	Loss (gain)
Price volatility	Buy	Increase (decrease)	Gain (loss)
Price volatility	Sell	Increase (decrease)	Loss (gain)

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Recurring Fair Value Measurements

The following table presents DESC’s assets and liabilities that are measured at fair value on a recurring basis for each hierarchy level, including both current and noncurrent portions:

(millions)	Level 1		Level 2		Level 3		Total
At March 31, 2025
Assets
Derivatives:
Commodity	$	—	$	2	$	275	$	277
Interest rate		—		2		—		2
Investments:
Cash equivalents and other		29		—		—		29
Total assets	$	29	$	4	$	275	$	308
Liabilities
Derivatives:
Commodity	$	—	$	—	$	5	$	5
Interest rate		—		2		—		2
Total liabilities	$	—	$	2	$	5	$	7
At December 31, 2024
Assets
Derivatives:
Commodity	$	—	$	—	$	370	$	370
Interest rate		—		2		—		2
Investments:
Cash equivalents and other		29		—		—		29
Total assets	$	29	$	2	$	370	$	401
Liabilities
Derivatives:
Interest rate	$	—	$	1	$	—	$	1
Total liabilities	$	—	$	1	$	—	$	1

The following table presents the net change in DESC’s assets and liabilities measured at fair value on a recurring basis and included in the Level 3 fair value category.

	Three Months Ended March 31,
	2025			2024
(millions)
Beginning balance	$	370		$	176
Total realized and unrealized gains (losses):
Included in earnings:
Purchased power		3			(2	)
Included in regulatory assets/liabilities		(89	)		70
Settlements		(14	)		2
Purchases		—			7
Ending balance	$	270		$	253

There are no unrealized gains and losses included in earnings in the Level 3 fair value category related to assets/liabilities still held at the reporting date for the three months ended March 31, 2025 and 2024.

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Fair Value of Financial Instruments

Substantially all of DESC’s financial instruments are recorded at fair value, with the exception of the instruments described below which are reported at historical cost. Estimated fair values have been determined using available market information and valuation methodologies considered appropriate by management. The carrying amount of financial instruments classified within current assets and current liabilities are representative of fair value because of the short-term nature of these instruments. For financial instruments that are not recorded at fair value, the carrying amounts and estimated fair values are as follows:

	March 31, 2025				December 31, 2024
(millions)	Carrying Amount		Estimated Fair Value(1)		Carrying Amount		Estimated Fair Value(1)
Long-term debt(2)	$	4,666	$	4,632	$	4,220	$	4,142
Affiliated long-term debt		230		230		230		230

(1)Fair value is estimated using market prices, where available, and interest rates currently available for issuance of debt with similar terms and remaining maturities. All fair value measurements are classified as Level 2. The carrying amount of debt issuances with short-term maturities and variable rates refinanced at current market rates is a reasonable estimate of their fair value.

(2)Carrying amount includes current portions, if any, included in securities due within one year and amounts which represent the unamortized debt issuance costs and discount or premium.

9. EMPLOYEE BENEFIT PLANS

In DESC’s Consolidated Statements of Comprehensive Income, the service cost component of net periodic benefit (credit) cost is reflected in other operations and maintenance expense with the non-service cost components reflected in other income (expense). Components of net periodic benefit cost (credit) recorded by DESC were as follows:

(millions)	Pension Benefits						Other Postretirement Benefits
Three Months Ended March 31,	2025			2024			2025			2024
Service cost	$	2		$	2		$	—		$	—
Interest cost		9			8			2			2
Expected return on assets		(10	)		(9	)		—			—
Amortization of actuarial losses		1			2			(1	)		(1	)
Net periodic benefit cost	$	2		$	3		$	1		$	1

During the three months ended March 31, 2025, DESC made less than $1 million of contributions to its qualified pension plan. During the three months ended March 31, 2024, DESC made no contributions to its pension trust. DESC expects to make $3 million of minimum required contributions to its qualified defined benefit pension plans in 2025 and expects to receive reimbursement for such contributions from Santee Cooper. DESC recovers current pension costs through either a rate rider that may be adjusted annually for retail electric operations or through cost of service rates for gas operations.

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10. COMMITMENTS AND CONTINGENCIES

As a result of issues generated in the ordinary course of business, DESC is involved in legal proceedings before various courts and is periodically subject to governmental examinations (including by regulatory authorities), inquiries and investigations. Certain legal proceedings and governmental examinations involve demands for unspecified amounts of damages, are in an initial procedural phase, involve uncertainty as to the outcome of pending appeals or motions or involve significant factual issues that need to be resolved, such that it is not possible for DESC to estimate a range of possible loss. For such matters that DESC cannot estimate, a statement to this effect is made in the description of the matter. Other matters may have progressed sufficiently through the litigation or investigative processes such that DESC is able to estimate a range of possible loss. For legal proceedings and governmental examinations that DESC is able to reasonably estimate a range of possible losses, an estimated range of possible loss is provided, in excess of the accrued liability (if any) for such matters. DESC maintains various insurance programs, including general liability insurance coverage which provides coverage for personal injury or wrongful death cases. Any accrued liability is recorded on a gross basis with a receivable also recorded for any probable insurance recoveries. Estimated ranges of loss are inclusive of legal fees and net of any anticipated insurance recoveries. Any estimated range is based on currently available information and involves elements of judgment and significant uncertainties. Any estimated range of possible loss may not represent DESC’s maximum possible loss exposure. The circumstances of such legal proceedings and governmental examinations will change from time to time and actual results may vary significantly from the current estimate. For current proceedings not specifically reported below, management does not anticipate that the liabilities, if any, arising from such proceedings would have a material effect on DESC’s financial position, liquidity or results of operations. During the three months ended March 31, 2025 and 2024, DESC recorded less than $1 million and $6 million, respectively, of charges in aggregate for various personal injury or wrongful death cases. DESC’s Consolidated Balance Sheets at March 31, 2025 and December 31, 2024 include $19 million and $10 million, respectively, of insurance receivables and $16 million and $7 million of reserves, respectively, primarily related to personal injury or wrongful death cases.

Environmental Matters

DESC is subject to costs resulting from a number of federal, state and local laws and regulations designed to protect human health and the environment. These laws and regulations affect future planning and existing operations. They can result in increased capital, operating and other costs as a result of compliance, remediation, containment and monitoring obligations.

From a regulatory perspective, DESC continually monitors and evaluates its current and projected emission levels and strives to comply with all state and federal regulations regarding those emissions. DESC participates in the SO2 and NOx emission allowance programs with respect to coal plant emissions and also has constructed additional pollution control equipment at its coal-fired electric generating plants. These actions are expected to address many of the rules and regulations discussed herein.

Air

The CAA, as amended, is a comprehensive program utilizing a broad range of regulatory tools to protect and preserve the nation’s air quality. At a minimum, states are required to establish regulatory programs to meet applicable requirements of the CAA. However, states may choose to develop regulatory programs that are more restrictive. Many of DESC’s facilities are subject to the CAA’s permitting and other requirements.

Carbon Regulations

In August 2016, the EPA issued a draft rule proposing to reaffirm that a source’s obligation to obtain a PSD or Title V permit for GHGs is triggered only if such permitting requirements are first triggered by non-GHG, or conventional, pollutants that are regulated by the New Source Review program, and exceed a significant emissions rate of 75,000 tons per year of CO2 equivalent emissions. Until the EPA ultimately takes final action on this rulemaking, DESC cannot predict the impact to its results of operations, financial condition and/or cash flows.

Water

The CWA, as amended, is a comprehensive program requiring a broad range of regulatory tools including a permit program to authorize and regulate discharges to surface waters with strong enforcement mechanisms. DESC must comply with applicable aspects of the CWA programs at its operating facilities.

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Regulation 316(b)

In October 2014, the final regulations under Section 316(b) of the CWA that govern existing facilities and new units at existing facilities that employ a cooling water intake structure and that have flow levels exceeding a minimum threshold became effective. The rule establishes a national standard for impingement based on seven compliance options, but forgoes the creation of a single technology standard for entrainment. Instead, the EPA has delegated entrainment technology decisions to state regulators. State regulators are to make case-by-case entrainment technology determinations after an examination of five mandatory facility-specific factors, including a social cost-benefit test, and six optional facility-specific factors. The rule governs all electric generating stations with water withdrawals above two MGD, with a heightened entrainment analysis for those facilities over 125 MGD. DESC has five facilities that are subject to the final regulations. DESC is also working with the EPA and state regulatory agencies to assess the applicability of Section 316(b) to five hydroelectric facilities. DESC anticipates that it may have to install impingement control technologies at certain of these stations that have once-through cooling systems. DESC is currently evaluating the need or potential for entrainment controls under the final rule as these decisions will be made on a case-by-case basis after a thorough review of detailed biological, technological and cost benefit studies. DESC is conducting studies and implementing plans as required by the rule to determine appropriate intake structure modifications at certain facilities to ensure compliance with this rule. While the impacts of this rule could be material to DESC’s results of operations, financial condition and/or cash flows, the existing regulatory framework in South Carolina provides rate recovery mechanisms that could substantially mitigate any such impacts for DESC.

Effluent Limitations Guidelines

In September 2015, the EPA released a final rule to revise the ELG Rule. The final rule established updated standards for wastewater discharges that apply primarily at coal and oil steam generating stations. Affected facilities are required to convert from wet to dry or closed cycle coal ash management, improve existing wastewater treatment systems and/or install new wastewater treatment technologies in order to meet the new discharge limits. In April 2017, the EPA granted two separate petitions for reconsideration of the final ELG Rule and stayed future compliance dates in the rule. Also in April 2017, the U.S. Court of Appeals for the Fifth Circuit granted the EPA’s request for a stay of the pending consolidated litigation challenging the rule while the EPA addresses the petitions for reconsideration. In September 2017, the EPA signed a rule to postpone the earliest compliance dates for certain waste streams regulations in the final ELG Rule from November 2018 to November 2020; however, the latest date for compliance for these regulations was December 2023. In October 2020, the EPA released the final rule that extended the latest dates for compliance with individual facilities’ compliance dates that would vary based on circumstances and the determination by state regulators and may range from 2021 to 2028. In May 2024, the EPA released a final rule revising the 2015 and 2020 Effluent Limitations Guidelines, establishing more stringent standards for wastewater discharges for the Steam Electric Power Generating Category, which apply primarily to wastewater discharges at coal and oil steam generating stations. Individual facilities’ compliance dates will vary based on circumstances and the determination by state regulators and may range to 2029, except in certain circumstances when a facility will be retired by 2034. DESC expects to complete wastewater treatment technology retrofits and modifications at the Williams generating station, with a similar project at the Wateree generation station under evaluation, to meet the requirements with the existing regulatory framework in South Carolina providing rate recovery mechanisms for costs of the projects. As discussed below, DESC recorded an increase to its AROs in the second quarter of 2024 in connection with the expected compliance costs associated with the EPA’s May 2024 final rule concerning CCR. DESC expects that such AROs would satisfy any AROs that would have otherwise been necessary for compliance with the EPA’s May 2024 Effluent Limitations Guidelines. DESC is currently unable to estimate what costs, if any, may be required in addition to the project for the Williams generating station, a potential project at the Wateree generating station and the recorded AROs to meet the requirements to operate certain facilities past 2034. However, DESC expects that while such costs for facility improvements, if required, could be material to its financial condition and/or cash flows, the existing regulatory framework in South Carolina provides rate recovery mechanisms that could substantially mitigate any such impacts.

Capacity Use Area

In November 2019, a new CUA was established in the counties surrounding the Cope Generating Station (Western Capacity Use Area) under the South Carolina Groundwater Use and Reporting Regulation. Under the regulation any groundwater well in a CUA that withdraws above three million gallons per month must be permitted. The Cope Generating Station is located within this new Western Capacity Use Area. Cope has been using four deep groundwater wells for cooling water and other house loads since 1996. Prior to designation of the new Western Capacity Use Area, the wells at Cope Station were only required to be registered not permitted. As a result of this designation, Cope will need to restore the surface water equipment to operable status to reduce reliance on groundwater wells. This includes completion of 316(b) requirements, (including SCDES BTA determination and modification of the station national pollutant discharge elimination system permit, which was obtained) and extensive inspection, repair and/or replacement of the associated surface water withdrawal equipment which has been idle since 1996. While the impacts of this rule change are potentially material to DESC’s results of operations, financial condition and/or cash flows, the existing regulatory framework in South Carolina provides rate recovery mechanisms that could substantially mitigate any such impacts for DESC.

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Waste Management and Remediation

The operations of DESC are subject to a variety of state and federal laws and regulations governing the management and disposal of solid and hazardous waste, and release of hazardous substances associated with current and/or historical operations. The CERCLA, as amended, and similar state laws, may impose joint, several and strict liability for cleanup on potentially responsible parties who owned, operated or arranged for disposal at facilities affected by a release of hazardous substances. In addition, many states have created programs to incentivize voluntary remediation of sites where historical releases of hazardous substances are identified and property owners or responsible parties decide to initiate cleanups.

From time to time, DESC may be identified as a potentially responsible party in connection with the alleged release of hazardous substances or wastes at a site. Under applicable federal and state laws, DESC could be responsible for costs associated with the investigation or remediation of impacted sites, or subject to contribution claims by other responsible parties for their costs incurred at such sites. DESC also may identify, evaluate and remediate other potentially impacted sites under voluntary state programs. Remediation costs may be subject to reimbursement under DESC’s insurance policies, rate recovery mechanisms, or both. Except as described below, DESC does not believe these matters will have a material effect on results of operations, financial condition and/or cash flows.

DESC has four decommissioned manufactured gas plant sites in South Carolina that are in various states of investigation, remediation and monitoring under work plans approved by, or under review by, the SCDES or the EPA. In the fourth quarter of 2023, DESC completed the majority of remediation activities at one site. DESC anticipates the remaining activities at that site will be completed in 2025 at an estimated cost of less than $1 million, after which the site will continue to incur ongoing maintenance and monitoring obligations. DESC expects to recover costs arising from the remediation work at all four sites through rate recovery mechanisms and as of March 31, 2025, deferred amounts, net of amounts previously recovered through rates and insurance settlements, totaled $33 million and are included in regulatory assets.

Ash Pond and Landfill Closure Costs

In April 2015, the EPA enacted a final rule regulating CCR landfills, existing ash ponds that still receive and manage CCRs and inactive ash ponds that do not receive, but still store, CCRs. DESC currently has inactive and existing CCR ponds and CCR landfills subject to the final rule at three different facilities. This rule created a legal obligation for DESC to retrofit or close all of its inactive and existing ash ponds over a certain period of time, as well as perform required monitoring, corrective action, and post-closure care activities as necessary.

In December 2016, legislation was enacted that creates a framework for EPA-approved state CCR permit programs. In August 2017, the EPA issued interim guidance outlining the framework for state CCR program approval. The EPA has enforcement authority until state programs are approved. The EPA and states with approved programs both will have authority to enforce CCR requirements under their respective rules and programs. In September 2017, the EPA agreed to reconsider portions of the CCR rule in response to two petitions for reconsideration. In March 2018, the EPA proposed certain changes to the CCR rule related to issues remanded as part of the pending litigation and other issues the EPA is reconsidering. Several of the proposed changes would allow states with approved CCR permit programs additional flexibility in implementing their programs. In July 2018, the EPA promulgated the first phase of changes to the CCR rule. In August 2018, the U.S. Court of Appeals for the D.C. Circuit issued its decision in the pending challenges of the CCR rule, vacating and remanding to the EPA three provisions of the rule. In May 2024, the EPA released a final rule to regulate inactive surface impoundments located at retired generating stations that contained CCR and liquids after October 2015, and certain other inactive or previously closed surface impoundments, landfills or other areas that contain accumulations of CCR. DESC believes that it may have inactive or closed units or areas that could be subject to the final rule at up to seven different stations. As discussed in Note 12 to the Consolidated Financial Statements in the Company's Annual Report on Form 10-K for the year ended December 31, 2024, DESC recorded adjustments in its AROs in 2024 in connection with this rule. The actual AROs related to CCRs may vary substantially from the estimates used to record the obligation.

Surety Bonds

At March 31, 2025, DESC had purchased $24 million of surety bonds. Under the terms of surety bonds, DESC is obligated to indemnify the respective surety bond company for any amounts paid.

23

11. OPERATING SEGMENTS

The Corporate and Other segment primarily includes specific items attributable to DESC’s operating segment that are not included in profit measures evaluated by executive management in assessing the segment’s performance or in allocating resources.

DESC’s CODM is Dominion Energy’s CEO. The CODM uses net income (loss) as the primary profit or loss measure at each segment. The CODM considers budget-to-actual variances on a quarterly basis when making decisions about allocating operating and capital resources to each segment, when assessing the performance of each segment and when determining the compensation of certain employees.

In the three months ended March 31, 2025 and 2024, DESC reported an insignificant amount of specific items in the Corporate and Other segment.

The following table presents segment information pertaining to DESC’s operations:

Three Months Ended March 31,	Dominion Energy South Carolina		Corporate and Other			Consolidated Total
(millions)
2025
Operating Revenue	$	986	$	—		$	986
Fuel used in electric generation(1)		204		—			204
Purchased power(1)		22		—			22
Gas purchased for resale(1)		126		—			126
Other operations and maintenance(1)		174		—			174
Depreciation and amortization(1)		140		—			140
Other taxes(1)		82		—			82
Total Operating Expenses		748		—			748
Other income (expense), net(2)		3		—			3
Interest charges, net of AFUDC(1)		71		—			71
Income tax expense(1)		18		2			20
Comprehensive Income Attributable to Noncontrolling Interest(2)		8		—			8
Comprehensive Income (Loss) Available (Attributable) to    Common Shareholder		144		(2	)		142
Capital expenditures		297		—			297
Total assets (billions)		17.1		—			17.1
2024
Operating Revenue	$	775	$	—		$	775
Fuel used in electric generation(1)		145		—			145
Purchased power(1)		10		—			10
Gas purchased for resale(1)		79		—			79
Other operations and maintenance(1)		163		—			163
Depreciation and amortization(1)		136		—			136
Other taxes(1)		78		—			78
Total Operating Expenses		611		—			611
Other income (expense), net(2)		1		—			1
Interest charges, net of AFUDC(1)		67		—			67
Income tax expense(1)		17		1			18
Comprehensive Income Attributable to Noncontrolling Interest(2)		6		—			6
Comprehensive Income (Loss) Available (Attributable) to    Common Shareholder		75		(1	)		74
Capital expenditures		268		—			268

(1)The significant expense categories and amounts in the segment information presented above align with the segment-level information that is regularly provided to DESC’s CODM.

(2)Items designated are other segment items for each reportable segment.

24

12. AFFILIATED AND RELATED PARTY TRANSACTIONS

DES, on behalf of itself and its parent company, provides the following services to DESC, which are rendered at direct or allocated cost: information systems, telecommunications, customer support, marketing and sales, human resources, corporate compliance, purchasing, financial, risk management, public affairs, legal, investor relations, gas supply and capacity management, strategic planning, general administrative and retirement benefits. Costs for these services include amounts capitalized. Amounts expensed are primarily recorded in other operations and maintenance - affiliated suppliers and other income (expense), net in the Consolidated Statements of Comprehensive Income.

DESC transacts with affiliates for certain quantities of electricity in the ordinary course of business. DESC also enters into certain commodity derivative contracts with affiliates. DESC uses these contracts, which are principally comprised of forward commodity purchases, to manage commodity price risks associated with purchases of electricity. See Note 7 for additional information.

	Three Months Ended March 31,
(millions)	2025		2024
Direct and allocated costs from DES(1)	$	62	$	53
Operating Revenues - Electric from sales to affiliate		1		1
Operating Expenses - Other taxes from affiliate		3		3
Purchases of electricity from solar affiliates		3		1

(1)Includes capitalized expenditures of $19 million and $12 million for the three months ended March 31, 2025 and 2024, respectively.

(millions)	March 31, 2025		December 31, 2024
Payable to DES	$	19	$	19
Payable to SCANA Corporation		7		7
Derivative assets with affiliates(1)		33		48

(1)Includes amounts recorded in current derivative assets of $6 million and $4 million as of March 31, 2025 and December 31, 2024, respectively, and amounts recorded in noncurrent derivative assets of $27 million and $44 million as of March 31, 2025 and December 31, 2024, respectively.

Borrowings from an affiliate are described in Note 5.

13. OTHER INCOME (EXPENSE), NET

Components of other income (expense), net are as follows:

	Three Months Ended March 31,
(millions)	2025			2024
Other income	$	5		$	2
Gains on sales of assets		—			1
Other expense		(2	)		(5	)
Allowance for equity funds used during construction		—			3
Other income (expense), net	$	3		$	1

25

ITEM 2. MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

MD&A discusses DESC’s results of operations. MD&A should be read in conjunction with DESC’s Consolidated Financial Statements. DESC meets the conditions to file under the reduced disclosure format, and therefore has omitted certain sections of MD&A.

Contents of MD&A

MD&A consists of the following information:

•Forward-Looking Statements

•Results of Operations

Forward-Looking Statements

This report contains statements concerning DESC’s expectations, plans, objectives, future financial performance and other statements that are not historical facts. These statements are “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. In most cases, the reader can identify these forward-looking statements by such words as “path,” “anticipate,” “estimate,” “forecast,” “expect,” “believe,” “should,” “could,” “plan,” “may,” “continue,” “target” or other similar words.

DESC makes forward-looking statements with full knowledge that risks and uncertainties exist that may cause actual results to differ materially from predicted results. Factors that may cause actual results to differ are often presented with the forward-looking statements themselves. Additionally, other factors may cause actual results to differ materially from those indicated in any forward-looking statement. These factors include but are not limited to:

•Unusual weather conditions and their effect on energy sales to customers and energy commodity prices;

•Extreme weather events and other natural disasters, including, but not limited to, hurricanes, high winds, severe storms, earthquakes, flooding, wildfires, climate changes and changes in water temperatures and availability that can cause outages and property damage to facilities;

•The impact of extraordinary external events, such as the pandemic health event resulting from COVID-19, and their collateral consequences, including extended disruption of economic activity in DESC’s markets and global supply chains;

•Federal, state and local legislative and regulatory developments;

•Changes in or interpretations of federal and state tax laws and regulations, including those related to tax credits or other incentives;

•Risks of operating businesses in regulated industries that are subject to changing regulatory structures;

•Changes to regulated rates collected;

•Timing and receipt of regulatory approvals necessary for planned construction or growth projects and compliance with conditions associated with such regulatory approvals;

•The inability to complete planned construction, conversion or growth projects at all, or with the outcomes or within the terms and time frames initially anticipated, including as a result of increased public involvement, intervention or litigation in such projects;

•Changes to federal, state and local environmental laws and regulations, including those related to climate change, the tightening of emission or discharge limits for GHGs and other substances, more extensive permitting requirements and the regulation of additional substances;

•Cost of environmental strategy and compliance, including those costs related to climate change;

•Changes in implementation and enforcement practices of regulators relating to environmental standards and litigation exposure for remedial activities;

•Difficulty in anticipating mitigation requirements associated with environmental and other regulatory approvals or related appeals;

•The impact of operational hazards, including adverse developments with respect to pipeline and plant safety or integrity, equipment loss, malfunction or failure, operator error and other catastrophic events;

26

•Risks associated with the operation of nuclear facilities, including costs associated with the disposal of spent nuclear fuel, decommissioning, plant maintenance and changes in existing regulations governing such facilities;

•Changes in operating, maintenance and construction costs;

•The availability of nuclear fuel, natural gas, purchased power or other materials utilized by DESC to provide electric generation, transmission and distribution and/or gas distribution services to its customers;

•Domestic terrorism and other threats to DESC’s physical and intangible assets, as well as threats to cybersecurity;

•Additional competition from the development and deployment of alternative energy sources, such as self-generation and distributed generation technologies;

•Competition in the development, construction and ownership of certain electric transmission facilities in connection with Order 1000;

•Changes in technology, particularly with respect to new, developing or alternative sources of generation and smart grid technologies;

•Changes in demand for services, including industrial, commercial and residential growth or decline in service areas, changes in customer growth or usage patterns, including as a result of energy conservation programs, the availability of energy efficient devices and the use of distributed generation methods;

•Adverse outcomes in litigation matters or regulatory proceedings;

•Counterparty credit and performance risk;

•Fluctuations in the value of investments held in nuclear decommissioning and benefit plan trusts;

•Fluctuations in energy-related commodity prices and the effect these could have on DESC’s liquidity position and the underlying value of its assets;

•Fluctuations in interest rates;

•Changes in rating agency requirements or credit ratings and their effect on availability and cost of capital;

•Global capital market conditions, including the availability of credit and the ability to obtain financing on reasonable terms;

•Political and economic conditions, including tariffs, inflation and deflation;

•Employee workforce factors including collective bargaining agreements and labor negotiations with union employees; and

•Changes in financial or regulatory accounting principles or policies imposed by governing bodies.

Additionally, other risks that could cause actual results to differ from predicted results are set forth in Part I. Item 1A. Risk Factors in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024.

DESC’s forward-looking statements are based on beliefs and assumptions using information available at the time the statements are made. DESC cautions the reader not to place undue reliance on its forward-looking statements because the assumptions, beliefs, expectations and projections about future events may, and often do, differ materially from actual results. DESC undertakes no obligation to update any forward-looking statement to reflect developments occurring after the statement is made.

Results of Operations

Presented below is a summary of DESC’s results:

	First Quarter
(millions)	2025		2024		$ Change
Net income	$	150	$	80	$	70

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Overview

First Quarter 2025 vs. 2024

Net income increased 88%, primarily due to an increase in non-fuel base rates associated with the settlement of the electric base rate case and an increase in sales to utility customers from weather.

Analysis of Consolidated Operations

Presented below are selected amounts related to DESC’s results of operations:

	First Quarter
(millions)	2025		2024		$ Change
Operating revenues	$	986	$	775	$	211
Fuel used in electric generation		204		145		59
Purchased power		22		10		12
Gas purchased for resale		126		79		47
Other operations and maintenance		174		163		11
Depreciation and amortization		140		136		4
Other taxes		82		78		4
Other income, net		3		1		2
Interest charges		71		67		4
Income tax expense		20		18		2

An analysis of DESC’s results of operations follows:

First Quarter 2025 vs. 2024

Operating revenues increased 27%, primarily reflecting:

•A $118 million increase in fuel-related revenue primarily as a result of an increase in commodity costs and purchased power costs associated with sales to electric utility retail customers ($71 million) and gas utility customers ($47 million);

•A $53 million increase in non-fuel base rates associated with the settlement of the electric base rate case;

•A $26 million increase in sales to electric utility retail customers from an increase in heating degree days during the heating season;

•A $6 million increase from electric utility customers who previously elected to pay market based or other negotiated rates; and

•A $6 million increase associated with increased infrastructure cost recovery under the Natural Gas Rate Stabilization Act.

Fuel used in electric generation increased 41%, primarily due to increased fuel costs associated with electric utility retail customers, which are offset in operating revenue and do not impact net income.

Purchased power increased $12 million, primarily due to an increase in costs associated with electric utility customers, which are offset in operating revenue and do not impact net income.

Gas purchased for resale increased 59%, primarily due to an increase in costs associated with gas utility customers, which are offset in operating revenue and do not impact net income.

Other operations and maintenance increased 7%, primarily due to an increase in salaries, wages and benefits and administrative expenses ($14 million), partially offset by the absence of charges associated with various personal injury or wrongful death litigation cases ($6 million).

Income tax expense increased 11%, primarily due to higher pre-tax income ($20 million), partially offset by a benefit associated with the remeasurement of an uncertain tax position ($18 million).

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ITEM 4. CONTROLS AND PROCEDURES

Senior management of DESC, including DESC’s CEO and CFO, evaluated the effectiveness of DESC’s disclosure controls and procedures as of the end of the period covered by this report. Based on this evaluation process, DESC’s CEO and CFO have concluded that DESC’s disclosure controls and procedures are effective.

There were no changes that occurred during the last fiscal quarter that materially affected, or are reasonably likely to materially affect, DESC’s internal control over financial reporting.

29

PART II. OTHER INFORMATION

ITEM 1. LEGAL PROCEEDINGS

From time to time, DESC is party to various legal, environmental or other regulatory proceedings, including in the ordinary course of business. SEC regulations require disclosure of certain environmental matters when a governmental authority is a party to the proceedings and such proceedings involve potential monetary sanctions that DESC reasonably believes will exceed a specified threshold. Pursuant to the SEC regulations, DESC uses a threshold of $1 million for such proceedings.

See the following for discussions on various legal, environmental and other regulatory proceedings to which DESC is a party, which information is incorporated herein by reference:

•Notes 3 and 12 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024.

•Notes 2 and 10 to the Consolidated Financial Statements in this report.

ITEM 1A. RISK FACTORS

DESC’s business is influenced by many factors that are difficult to predict, involve uncertainties that may materially affect actual results and are often beyond its control. A number of these risk factors have been identified in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024, which should be taken into consideration when reviewing the information contained in this report. There have been no material changes with regard to the risk factors previously disclosed in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024. For other factors that may cause actual results to differ materially from those indicated in any forward-looking statement or projection contained in this report, see Forward-Looking Statements in MD&A in this report.

ITEM 5. OTHER INFORMATION

During the last fiscal quarter, none of DESC’s directors or officers (as defined in Rule 16a-1(f) under the Exchange Act) adopted or terminated a “Rule 10b5-1 trading arrangement” or “non-Rule 10b5-1 trading arrangement,” as each term is defined in Item 408(a) of Regulation S-K.

30

ITEM 6. EXHIBITS

Exhibit No.	Description
3.1	Amended and Restated Articles of Incorporation, effective April 29, 2019 (Exhibit 3.1, Form 8-K filed April 29, 2019, File No. 1-3375).
3.2	Amended and Restated Bylaws, effective April 29, 2019 (Exhibit 3.2, Form 8-K filed April 29, 2019, File No. 1-3375).
4.1	Dominion Energy South Carolina, Inc. agrees to furnish to the U.S. Securities and Exchange Commission upon request any instrument with respect to long-term debt as to which the total amount of securities authorized does not exceed 10% of its total consolidated assets.
31.a	Certification by Chief Executive Officer of Dominion Energy South Carolina, Inc. pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 (filed herewith).
31.b	Certification by Chief Financial Officer of Dominion Energy South Carolina, Inc. pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 (filed herewith).
32.a	Certification to the Securities and Exchange Commission by Chief Executive Officer and Chief Financial Officer of Dominion Energy South Carolina, Inc. as required by Section 906 of the Sarbanes-Oxley Act of 2002 (furnished herewith).
101	The following financial statements from Dominion Energy South Carolina, Inc.’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2025, filed on May 1, 2025, formatted in iXBRL (Inline eXtensible Reporting Language): (i) Consolidated Balance Sheets, (ii) Consolidated Statements of Comprehensive Income, (iii) Consolidated Statements of Cash Flows, (iv) Consolidated Statements of Changes in Common Equity, and (v) the Notes to Consolidated Financial Statements.
104	Cover Page Interactive Data File (formatted in iXBRL (Inline eXtensible Reporting Language) and contained in Exhibit 101).

31

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

	DOMINION ENERGY SOUTH CAROLINA, INC.
		(Registrant)
	By:	/s/ Michele L. Cardiff
Date: May 1, 2025		Michele L. Cardiff
		Senior Vice President, Controller and Chief Accounting Officer

32

EX-31.A

Exhibit 31.a

I, Edward H. Baine, certify that:

1. I have reviewed this report on Form 10-Q of Dominion Energy South Carolina, Inc.;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant's other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c) Evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(d) Disclosed in this report any change in the registrant's internal control over financial reporting that occurred during the registrant's most recent fiscal quarter (the registrant's fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting; and

5. The registrant's other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

(a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

(b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

Date: May 1, 2025	/s/ Edward H. Baine
	Edward H. Baine Chief Executive Officer

EX-31.B

Exhibit 31.b

I, Steven D. Ridge, certify that:

1. I have reviewed this report on Form 10-Q of Dominion Energy South Carolina, Inc.;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant's other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c) Evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(d) Disclosed in this report any change in the registrant's internal control over financial reporting that occurred during the registrant's most recent fiscal quarter (the registrant's fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting; and

5. The registrant's other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

(a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

(b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

Date: May 1, 2025	/s/ Steven D. Ridge
	Steven D. Ridge Executive Vice President and Chief Financial Officer

EX-32.A

Exhibit 32.a

CERTIFICATION PURSUANT TO
18 U.S.C. SECTION 1350,
AS ADOPTED PURSUANT TO
SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

Pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, each of the undersigned officers of Dominion Energy South Carolina, Inc. (the “Company”), certify that:

1.the Quarterly Report on Form 10-Q for the quarter ended March 31, 2025 (the “Report”), of the Company to which this certification is an exhibit fully complies with the requirements of section 13(a) or 15(d) of the Securities Exchange Act of 1934 (15 U.S.C. 78m(a) or 78o(d)).

2.the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company as of March 31, 2025, and for the period then ended.

/s/ Edward H. Baine

Edward H. Baine
Chief Executive Officer
May 1, 2025

/s/ Steven D. Ridge

Steven D. Ridge
Executive Vice President and
Chief Financial Officer
May 1, 2025

XML

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2025	Apr. 25, 2025
Cover [Abstract]
Entity Registrant Name	DOMINION ENERGY SOUTH CAROLINA, INC.
Entity Central Index Key	0000091882
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-Q
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		40,296,147
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-3375
Entity Tax Identification Number	57-0248695
Entity Address, Address Line One	220 OPERATION WAY
Entity Address, City or Town	CAYCE
Entity Address, State or Province	SC
Entity Address, Postal Zip Code	29033
City Area Code	804
Local Phone Number	819-2284
Entity Incorporation, State or Country Code	SC
Document Quarterly Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes
Document Period End Date	Mar. 31, 2025

XML

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions		Mar. 31, 2025	Dec. 31, 2024
ASSETS
Utility plant in service		$ 16,488	$ 16,300
Accumulated depreciation and amortization		(5,809)	(5,761)
Construction work in progress		913	899
Nuclear fuel, net of accumulated amortization		215	224
Utility plant, net		11,807	11,662
Nonutility Property and Investments:
Nonutility property, net of accumulated depreciation		16	16
Assets held in trust, nuclear decommissioning		269	268
Nonutility property and investments, net		285	284
Current Assets:
Cash and cash equivalents		7	0
Customer, net of allowance for uncollectible accounts of $8 and $6		403	423
Receivables, other		87	104
Inventories (at average cost):
Fuel		88	83
Gas storage		19	22
Materials and supplies		214	211
Prepayments		81	91
Derivative assets	[1]	73	63
Regulatory assets		340	299
Other current assets		15	16
Total current assets		1,330	1,316
Deferred Debits and Other Assets:
Derivative assets	[1]	206	309
Regulatory assets		3,362	3,342
Affiliated receivables		26	26
Other		102	102
Total deferred debits and other assets		3,696	3,779
Total assets		17,118	17,041
CAPITALIZATION AND LIABILITIES
Common Stock - no par value		4,338	4,088
Retained earnings		831	689
Accumulated other comprehensive loss		(1)	(1)
Total common equity		5,168	4,776
Noncontrolling interest		214	206
Total equity		5,382	4,982
Long-term debt, net		4,666	4,220
Affiliated long-term debt		230	230
Finance leases		2	2
Total long-term debt		4,898	4,452
Total capitalization		10,280	9,434
Current Liabilities:
Short-term borrowings		210	250
Securities due within one year		2	2
Accounts payable		201	273
Affiliated and related party payables		623	995
Customer deposits and customer prepayments		75	82
Taxes accrued		73	254
Interest accrued		90	83
Regulatory liabilities		227	201
Derivative liabilities		1	0
Other		159	201
Total current liabilities		1,661	2,341
Deferred Credits and Other Liabilities:
Deferred income taxes and investment tax credits		1,447	1,409
Asset retirement obligations		1,142	1,139
Pension and other postretirement benefits		109	109
Derivative liabilities		6	1
Regulatory liabilities		2,361	2,488
Other		112	120
Total deferred credits and other liabilities		5,177	5,266
Commitments and Contingencies
Total capitalization and liabilities		17,118	17,041
Related Party
Current Assets:
Affiliated and related party		$ 3	$ 4

[1] See Note 12 for amounts attributable to affiliates.

XML

Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) shares in Millions, $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Utility plant, net	$ 11,807	$ 11,662
Receivables, customer, allowance for uncollectible accounts	8	6
Total current assets	1,330	1,316
Total deferred debits and other assets	$ 3,696	$ 3,779
Common stock, par value	$ 0	$ 0
Common stock, shares outstanding	40.3	40.3
Variable Interest Entity, Primary Beneficiary [Member]
Utility plant, net	$ 822	$ 824
Total current assets	83	79
Total deferred debits and other assets	$ 27	$ 25

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Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2025	Mar. 31, 2024
Income Statement [Abstract]
Operating Revenue	[1]	$ 986	$ 775
Operating Expenses:
Fuel used in electric generation	[2]	204	145
Purchased power	[1],[2]	22	10
Gas purchased for resale	[2]	126	79
Other operations and maintenance		131	122
Other operations and maintenance - affiliated suppliers		43	41
Depreciation and amortization	[2]	140	136
Other taxes	[1],[2]	82	78
Total operating expenses		748	611
Operating income		238	164
Other income (expense), net	[3]	3	1
Interest charges, net of AFUDC of $6 and $4	[1]	71	67
Income before income tax expense		170	98
Income tax expense	[2]	20	18
Net Income and Other Comprehensive Income		150	80
Comprehensive Income Attributable to Noncontrolling Interest	[3]	8	6
Comprehensive Income Available to Common Shareholder		$ 142	$ 74

[1] See Note 12 for amounts attributable to affiliates.

[2] The significant expense categories and amounts in the segment information presented above align with the segment-level information that is regularly provided to DESC’s CODM.

[3] Items designated are other segment items for each reportable segment.

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Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Income Statement [Abstract]
Allowance for funds used during construction	$ 6	$ 4

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Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2025	Mar. 31, 2024
Operating Activities
Net income		$ 150	$ 80
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred income taxes, net		38	5
Depreciation and amortization		140	136
Amortization of nuclear fuel		10	9
Other adjustments		5	0
Changes in certain assets and liabilities:
Receivables		29	45
Receivables - affiliated and related party		1	1
Inventories		(4)	(1)
Prepayments and deposits, net		3	2
Regulatory assets		(98)	79
Regulatory liabilities		(100)	41
Accounts payable		(34)	(18)
Accounts payable - affiliated and related party		12	43
Taxes accrued		(181)	(177)
Interest accrued		7	2
Net realized and unrealized changes related to commodity derivative activities		98	(78)
Pension and other postretirement benefits		0	(1)
Other assets and liabilities		(22)	(2)
Net cash provided by operating activities		54	166
Investing Activities
Property additions and construction expenditures		(297)	(268)
Proceeds from investments and sales or disposals of assets, including asset retirement costs		(23)	(13)
Purchase of investments		0	(5)
Other		1	0
Net cash used in investing activities		(319)	(286)
Financing Activities
Proceeds from issuance of debt		450	0
Dividend to parent		0	(62)
Contribution from parent		250	0
Short-term borrowings, net		(40)	(44)
Short-term borrowings - affiliated, net		(384)	230
Other		(4)	(1)
Net cash provided by financing activities		272	123
Net increase in cash, restricted cash and equivalents		7	3
Cash, restricted cash and equivalents at beginning of period	[1]	0	1
Cash, restricted cash and equivalents at end of period	[1]	7	4
Significant noncash investing and financing activities:
Accrued construction expenditures		73	56
Operating leases	[2]	$ 4	$ 0

[1] At March 31, 2025, December 31, 2024, March 31, 2024 and December 31, 2023 there were no restricted cash and equivalents balances.

[2] Finance leases entered into, if any, were inconsequential for all periods presented.

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Consolidated Statements of Cash Flows (Unaudited) (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023
Statement of Cash Flows [Abstract]
Restricted cash and equivalents	$ 0	$ 0	$ 0	$ 0

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Consolidated Statements of Changes in Common Equity (Unaudited) - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Retained Earnings	AOCI	Noncontrolling Interest
Beginning balance at Dec. 31, 2023	$ 4,862	$ 4,088	$ 592	$ (1)	$ 183
Beginning balance (in shares) at Dec. 31, 2023		40
Total comprehensive income available to common shareholder	80		74		6
Dividend to parent	(62)		(62)
Ending balance at Mar. 31, 2024	4,880	$ 4,088	604	(1)	189
Ending balance (in shares) at Mar. 31, 2024		40
Beginning balance at Dec. 31, 2024	4,982	$ 4,088	689	(1)	206
Beginning balance (in shares) at Dec. 31, 2024		40
Total comprehensive income available to common shareholder	150		142		8
Capital contribution from parent	250	$ 250
Ending balance at Mar. 31, 2025	$ 5,382	$ 4,338	$ 831	$ (1)	$ 214
Ending balance (in shares) at Mar. 31, 2025		40

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Pay vs Performance Disclosure - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Pay vs Performance Disclosure
Net Income (Loss)	$ 142	$ 74

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Insider Trading Arrangements	3 Months Ended
	Mar. 31, 2025
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

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Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2025

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Basis of Consolidation and Variable Interest Entities

DESC has determined that it has a controlling financial interest in each of GENCO and Fuel Company (which are considered to be VIEs) and, accordingly, DESC’s Consolidated Financial Statements include, after eliminating intercompany balances and transactions, the accounts of DESC, GENCO and Fuel Company. See Note 2 to the Consolidated Financial Statements included in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024 for a description of GENCO and Fuel Company.

DESC purchases shared services from DES, an affiliated VIE that provides accounting, legal, finance and certain administrative and technical services to all Dominion Energy subsidiaries, including DESC. DESC has determined that it is not the primary beneficiary of DES as it does not have either the power to direct the activities that most significantly impact its economic performance or an obligation to absorb losses and benefits which could be significant to it. See Note 12 for amounts attributable to affiliates.

Significant Accounting Policies

There have been no significant changes from Note 2 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024.

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Rate and Other Regulatory Matters

3 Months Ended

Mar. 31, 2025

Regulated Operations [Abstract]

Rate and Other Regulatory Matters

2. RATE AND OTHER REGULATORY MATTERS

Regulatory Matters Involving Potential Loss Contingencies

As a result of issues generated in the ordinary course of business, DESC is involved in various regulatory matters. Certain regulatory matters may ultimately result in a loss; however, as such matters are in an initial procedural phase, involve uncertainty as to the outcome of pending reviews or orders, and/or involve significant factual issues that need to be resolved, it is not possible for DESC to estimate a range of possible loss. For regulatory matters that DESC cannot estimate, a statement to this effect is made in the description of the matter. Other matters may have progressed sufficiently through the regulatory process such that DESC is able to estimate a range of possible loss. For regulatory matters that DESC is able to reasonably estimate a range of possible losses, an estimated range of possible loss is provided, in excess of the accrued liability (if any) for such matters. Any estimated range is based on currently available information, involves elements of judgment and significant uncertainties and may not represent DESC’s maximum possible loss exposure. The circumstances of such regulatory matters will change from time to time and actual results may vary significantly from the current estimate. For current matters not specifically reported below, management does not anticipate that the outcome from such matters would have a material effect on DESC’s financial position, liquidity or results of operations.

Other Regulatory Matters

Other than the following matters, there have been no significant developments regarding the pending regulatory matters disclosed in Note 3 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024.

Electric – Cost of Fuel

DESC’s retail electric rates include a cost of fuel component approved by the South Carolina Commission which may be adjusted periodically to reflect changes in the price of fuel purchased by DESC. In February 2025, DESC filed with the South Carolina Commission a proposal to increase the total fuel cost component of retail electric rates. DESC’s proposed adjustment is designed to recover DESC’s current base fuel costs, including its existing under-collected balance, over the 12-month period beginning with the first billing cycle of May 2025. In addition, DESC proposed an increase to its variable environmental and avoided capacity cost component. The net effect is a proposed annual increase of $154 million. In March 2025, DESC and the South Carolina Office of Regulatory Staff filed a settlement agreement with the South Carolina Commission for approval to make certain adjustments to the February 2025 filing that would result in an inconsequential change to the proposed annual increase. In April 2025, the South Carolina Commission approved the settlement agreement, with rates effective with the first billing cycle of May 2025.

Electric - Transmission Project

In December 2024, DESC filed an application with the South Carolina Commission requesting approval of a CPCN to construct and operate the Ritter - Yemassee Transmission Line #2, comprised of a 17-mile 230 kV transmission line and associated facilities in Colleton and Hampton Counties, South Carolina with an estimated total project cost of $55 million. In April 2025, the South Carolina Commission approved the application.

Electric – Other

DESC has approval for a DSM rider through which it recovers expenditures related to its DSM programs. In January 2025, DESC filed an application with the South Carolina Commission seeking approval to recover $46 million of costs and net lost revenues associated with these programs, along with an incentive to invest in such programs. DESC requested that rates be effective with the first billing cycle of May 2025. In April 2025, the South Carolina Commission approved the request, effective with the first billing cycle of May 2025.

DESC utilizes a pension costs rider approved by the South Carolina Commission which is designed to allow recovery of projected pension costs, including under-collected balances or net of over-collected balances, as applicable. The rider is typically reviewed for adjustment every 12 months with any resulting increase or decrease going into effect beginning with the first billing cycle in May. In February 2025, DESC requested that the South Carolina Commission approve an adjustment to this rider to decrease annual revenue by $13 million. In April 2025, the South Carolina Commission approved the request.

Regulatory Assets and Regulatory Liabilities

Rate-regulated utilities recognize in their financial statements certain revenues and expenses in different periods than do other enterprises. As a result, DESC has recorded regulatory assets and regulatory liabilities which are summarized in the following table. Except for NND Project costs and certain other unrecovered costs referenced herein, substantially all regulatory assets are either explicitly excluded from rate base or are effectively excluded from rate base due to their being offset by related liabilities.

	March 31,		December 31,
(millions)	2025		2024
Regulatory assets:
NND Project costs(1)	$	138	$	138
AROs(2)		6		8
Deferred employee benefit plan costs(3)		5		8
Other unrecovered plant(4)		18		18
DSM programs(5)		23		24
Cost of fuel and purchased gas under-collections(6)		92		35
Other		58		68
Regulatory assets - current		340		299
NND Project costs(1)		1,776		1,811
AROs(2)		704		695
Deferred employee benefit plan costs(3)		96		94
Interest rate hedges(7)		167		167
Other unrecovered plant(4)		94		89
DSM programs(5)		48		49
Environmental remediation costs(8)		42		42
Deferred storm damage costs(9)		77		76
Deferred transmission operating costs(10)		71		72
Derivatives(11)		94		95
Other(12)		193		152
Regulatory assets - noncurrent		3,362		3,342
Total regulatory assets	$	3,702	$	3,641
Regulatory liabilities:
Monetization of guaranty settlement(13)	$	67	$	67
Income taxes refundable through future rates(14)		17		24
Reserve for refunds to electric utility customers(15)		67		73
Derivatives(11)		44		27
Other		32		10
Regulatory liabilities - current		227		201
Monetization of guaranty settlement(13)		552		568
Income taxes refundable through future rates(14)		838		820
Asset removal costs(16)		597		598
Reserve for refunds to electric utility customers(15)		146		161
Derivatives(11)		223		328
Other		5		13
Regulatory liabilities - noncurrent		2,361		2,488
Total regulatory liabilities	$	2,588	$	2,689

(1)Reflects expenditures associated with the NND Project, which pursuant to the SCANA Merger Approval Order, will be recovered from electric service customers over a 20-year period ending in 2039.

(2)Represents uncollected costs, including deferred depreciation and accretion expense, related to legal obligations associated with the future retirement of generation, transmission and distribution properties. The AROs primarily relate to DESC’s electric generating facilities, including Summer, and are expected to be recovered over the related property lives and periods of decommissioning which may range up to approximately 105 years. In addition, the balance reflects amounts related to the EPA’s May 2024 final rule concerning CCR as discussed in Note 10.

(3)Employee benefit plan costs have historically been recovered as they have been recorded under GAAP. Deferred employee benefit plan costs represent amounts of pension and other postretirement benefit costs which were accrued as liabilities and treated as regulatory assets pursuant to FERC guidance, and costs deferred pursuant to specific South Carolina Commission regulatory orders. Based on rates currently in effect, DESC expects to recover certain deferred benefit costs through utility rates over average service periods of participating employees, which is approximately 11 years. DESC expects to recover other deferred pension costs through utility rates over periods through 2044.

(4)Represents the carrying value of coal-fired generating units, including related materials and supplies inventory, retired from service prior to being fully depreciated. DESC is amortizing these amounts through cost of service rates following depreciation amounts that were designed to recover the retired units cost over their previous estimated remaining useful lives, which has been estimated to be through 2025. Based on current projections of remaining decommissioning costs, projected recovery is expected to extend through 2039. In addition, amounts include unrecovered costs of existing meters and equipment retired from service prior to being fully depreciated as part of the Advanced Metering Infrastructure project, which are being recovered through rates through 2028. This amount also includes certain inventory and preliminary survey and investigation charges being amortized through 2026 related to the transition or conversion from coal to gas fired generation at certain facilities. The majority of unamortized amounts are included in rate base and are earning a current return.

(5)Primarily represents deferred costs associated with electric demand reduction programs, and such deferred costs are currently being recovered over three years through an approved rate rider.

(6)Represents amounts under- or over-collected from customers pursuant to the cost of fuel and purchased gas components approved by the South Carolina Commission.

(7)Represents settled interest rate derivatives designated as cash flow hedges expected to be amortized to interest expense over the lives of the underlying debt through 2065.

(8)Reflects amounts associated with the assessment and clean-up of sites currently or formerly owned by DESC. Such remediation costs are expected to be recovered over periods of up to 24 years. See Note 10 for additional information.

(9)Represents storm restoration costs for which DESC expects to receive future recovery. Pursuant to the settlement agreement approved in DESC’s retail electric base rate case in August 2024, for costs incurred prior to September 2024, DESC expects to receive future recovery through customer rates through 2034 and for costs incurred effective September 2024, DESC expects to receive future recovery through customer rates of approximately $2 million each year. Unamortized amounts are included in rate base and are earning a current return.

(10)Includes deferred depreciation and property taxes associated with certain transmission assets for which DESC expects future recovery from customers through 2062. Unamortized amounts are included in rate base and earning a current return.

(11)Represents changes in the fair value of derivatives, excluding separately presented interest rate hedges, that following settlement are expected to be recovered from or refunded to customers.

(12)Various other regulatory assets are expected to be recovered through rates over varying periods through 2078.

(13)Represents proceeds related to the monetization of the Toshiba Settlement. In accordance with the SCANA Merger Approval Order, this balance, net of amounts that may be required to satisfy liens, will be refunded to electric customers over a 20-year period ending in 2039.

(14)Includes (i) excess deferred income taxes arising from the remeasurement of deferred income taxes in connection with the enactment of the 2017 Tax Reform Act (certain of which are protected under normalization rules and will be amortized over the remaining lives of related property, and certain of which will be amortized to the benefit of customers over prescribed periods as instructed by regulators) and (ii) deferred income taxes arising from investment tax credits, offset by (iii) deferred income taxes that arise from utility operations that have not been included in customer rates (a portion of which relate to depreciation and are expected to be recovered over the remaining lives of the related property which may range up to 85 years).

(15)Reflects amounts previously collected from retail electric customers of DESC for the NND Project to be credited to customers over an estimated 11-year period effective February 2019 in connection with the SCANA Merger Approval Order.

(16)Represents estimated net collections through depreciation rates of amounts to be expended for the removal of assets in the future.

Regulatory assets have been recorded based on the probability of their recovery. All regulatory assets represent incurred costs that may be deferred under GAAP for regulated operations. The South Carolina Commission or FERC has reviewed and approved through specific orders certain of the items shown as regulatory assets. In addition, regulatory assets include, but are not limited to, certain costs which have not been specifically approved for recovery by one of these regulatory agencies. While such costs are not currently being recovered, management believes that they would be allowable under existing rate-making concepts embodied in rate orders or applicable state law and expects to recover these costs through rates in future periods.

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Operating Revenue

3 Months Ended

Mar. 31, 2025

Revenues [Abstract]

Operating Revenue

3. OPERATING REVENUE

DESC’s revenue consists of the following:

Three Months Ended March 31,	2025				2024
(millions)	Electric		Gas		Electric		Gas
Customer class:
Residential	$	371	$	151	$	283	$	117
Commercial		228		54		188		41
Industrial		109		27		87		18
Other		32		8		28		6
Revenues from contracts with customers		740		240		586		182
Other revenues		6		—		7		—
Total Operating Revenues	$	746	$	240	$	593	$	182

Contract liabilities represent the obligation to transfer goods or services to a customer for which consideration has already been received from the customer. DESC had contract liability balances of $5 million and $6 million at March 31, 2025 and December 31, 2024, respectively. During both the three months ended March 31, 2025 and 2024, DESC recognized revenue of $3 million from the beginning contract liability balances as DESC fulfilled its obligations to provide service to its customers. Contract liabilities are recorded in customer deposits and customer prepayments in the Consolidated Balance Sheets.

Balances and activity related to contract costs deferred as regulatory assets were as follows:

	Regulatory Assets
(millions)	March 31, 2025		December 31, 2024
Beginning balance	$	10	$	11
Additional costs		4		—
Amortization		—		(1	)
Ending balance	$	14	$	10

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Equity

3 Months Ended

Mar. 31, 2025

Equity [Abstract]

Equity

4. EQUITY

For all periods presented, DESC’s authorized shares of common stock, no par value, were 50 million, of which 40.3 million were issued and outstanding, and DESC’s authorized shares of preferred stock, no par value, were 20 million, of which 1,000 shares were issued and outstanding. All outstanding shares of common and preferred stock are held by SCANA.

There have been no material changes to the dividend restrictions affecting DESC described in Note 5 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024.

During the first quarter of 2025, DESC received equity contributions of $250 million from Dominion Energy. DESC primarily used these funds for working capital needs including reducing short-term debt.

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Long-Term and Short-Term Debt

3 Months Ended

Mar. 31, 2025

Debt Disclosure [Abstract]

Long-Term and Short-Term Debt

5. LONG-TERM AND SHORT-TERM DEBT

DESC’s short-term financing is supported through its access as co-borrower to Dominion Energy’s $7.0 billion joint revolving credit facility, as amended April 2025. The credit facility can be used for working capital, as support for the combined commercial paper programs of the borrowers under the credit facility and for other general corporate purposes. Other than the items discussed below, there have been no significant changes from Note 6 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024.

At March 31, 2025, DESC’s share of commercial paper and letters of credit outstanding under its joint credit facility with Dominion Energy was as follows:

(millions)	Maximum Facility Sub-Limit		Outstanding Commercial Paper		Outstanding Letters of Credit
Joint revolving credit facility(1)	$	1,000	$	210	$	—

(1)A maximum of $1.0 billion of the facility is available to DESC, assuming adequate capacity is available after giving effect to uses by co-borrowers Dominion Energy and Virginia Power. A sub-limit for DESC is set within the facility limit but can be changed at the option of the co-borrowers multiple times per year. At March 31, 2025, the sub-limit for DESC was $500 million. In April 2025, the sub-limit was increased up to $1.0 billion. If DESC has liquidity needs in excess of its sub-limit, the sub-limit may be changed provided that it does not exceed $1.0 billion or such needs may be satisfied through short-term borrowings from Dominion Energy. This credit facility, as amended in April 2025, matures in April 2030, with the potential to be extended by the borrowers to April 2032. The credit facility can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $3.0 billion (or the sub-limit, whichever is less) of letters of credit.

In March 2025, FERC granted DESC authority through March 2027 to issue short-term indebtedness (pursuant to Section 204 of the Federal Power Act) in amounts not to exceed $1.8 billion outstanding with maturity dates of one year or less. At March 31, 2025, DESC had issued $210 million in commercial paper supported by its joint revolving credit facility with Dominion Energy as disclosed above and had drawn on $227 million of its intercompany credit facility with Dominion Energy, as permitted by this FERC authorization. In addition, in March 2025, FERC granted GENCO authority through March 2027 to issue short-term indebtedness not to exceed $300 million outstanding with maturity dates of one year or less. At March 31, 2025, GENCO had drawn on $63 million of its intercompany credit facility with Dominion Energy, as permitted by this FERC authorization.

DESC is obligated with respect to an aggregate of $68 million of industrial revenue bonds which are secured by letters of credit. These letters of credit expire, subject to renewal, in the fourth quarter of 2025.

DESC, GENCO and Fuel Company each have intercompany credit facilities with Dominion Energy with a maximum capacity of $900 million, $200 million and $400 million, respectively. At March 31, 2025 and December 31, 2024, DESC, GENCO and Fuel Company collectively had borrowings outstanding under these agreements totaling $558 million and $942 million, respectively, which are recorded in affiliated and related party payables in DESC’s Consolidated Balance Sheets. Interest charges associated with these agreements were $11 million and $10 million for the three months ended March 31, 2025 and 2024, respectively.

In January 2025, DESC issued $450 million of 5.30% first mortgage bonds that mature in 2035. The proceeds were used for general corporate purposes and/or to repay short-term debt.

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Income Taxes

3 Months Ended

Mar. 31, 2025

Income Tax Disclosure [Abstract]

Income Taxes

6. INCOME TAXES

For continuing operations, including noncontrolling interests, the statutory U.S. federal income tax rate reconciles to DESC’s effective income tax rate as follows:

Three Months Ended March 31,	2025			2024
U.S. statutory rate		21.0	%		21.0	%
Increases (reductions) resulting from:
State taxes, net of federal benefit		10.8			3.9
Reversal of excess deferred income taxes		(2.4	)		(5.3	)
Allowance for equity funds used during construction		—			(0.7	)
Remeasurements and settlements of uncertain tax positions		(17.5	)	—
Other, net		(0.2	)	—
Effective tax rate		11.7	%		18.9	%

As of March 31, 2025, DESC’s effective tax rate reflects an income tax net benefit of $18 million reflecting a $30 million remeasurement of an unrecognized tax benefit partially deferred to regulatory liabilities. See Note 7 to the Consolidated Financial Statements in DESC's Annual Report on Form 10-K for the year ended December 31, 2024, for a discussion of these unrecognized tax benefits.

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Derivative Financial Instruments

3 Months Ended

Mar. 31, 2025

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative Financial Instruments

7. DERIVATIVE FINANCIAL INSTRUMENTS

DESC’s accounting policies, objectives, and strategies for using derivative instruments are discussed in Note 2 in the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024. See Note 8 for further information about fair value measurements and associated valuation methods for derivatives.

Cash collateral, as presented in the table below, is used to offset derivative assets and liabilities when applicable. Certain of DESC’s derivative instruments contain credit-related contingent provisions. These provisions require DESC to provide collateral upon the occurrence of specific events, primarily a credit rating downgrade. If the credit-related contingent features underlying the instruments that are in a liability position and not fully collateralized with cash were fully triggered as of March 31, 2025 and December 31, 2024, DESC would have been required to post $2 million and $1 million, respectively, of additional collateral to its counterparties. The collateral that would be required to be posted includes the impacts of any offsetting asset positions and any amounts already posted for derivatives and non-derivative contracts per contractual terms. DESC had not posted any collateral at March 31, 2025 and December 31, 2024 related to derivatives with credit-related contingent provisions that are in a liability position and not fully collateralized with cash. The aggregate fair value of all derivative instruments with credit-related contingent provisions that are in a liability position and not fully collateralized with cash as of March 31, 2025 and December 31, 2024 was $2 million and $1 million, respectively, which does not include the impact of any offsetting asset positions.

The table below presents derivative balances by type of financial instrument, if the gross amounts recognized in the Consolidated Balance Sheets were netted with derivative instruments and cash collateral received or paid:

	March 31, 2025								December 31, 2024
	Gross Amounts Not Offset in the Consolidated Balance Sheet								Gross Amounts Not Offset in the Consolidated Balance Sheet
(millions)	Gross Assets Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Received		Net Amounts		Gross Assets Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Received		Net Amounts
Interest rate contracts:
Over-the-counter	$	2	$	—	$	—	$	2	$	2	$	—	$	—	$	2
Commodity contracts:
Over-the-counter	$	78	$	—	$	—	$	78	$	81	$	—	$	—	$	81
Total derivatives	$	80	$	—	$	—	$	80	$	83	$	—	$	—	$	83

(1)Excludes derivative assets of $199 million and $289 million at March 31, 2025 and December 31, 2024, respectively, which are not subject to master netting or similar arrangements.

	March 31, 2025								December 31, 2024
	Gross Amounts Not Offset in the Consolidated Balance Sheet								Gross Amounts Not Offset in the Consolidated Balance Sheet
(millions)	Gross Liabilities Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Paid		Net Amounts		Gross Liabilities Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Paid		Net Amounts
Interest rate contracts:
Over-the-counter	$	2	$	—	$	—	$	2	$	1	$	—	$	—	$	1
Total derivatives	$	2	$	—	$	—	$	2	$	1	$	—	$	—	$	1

(1)Excludes derivative liabilities of $5 million at March 31, 2025, which are not subject to master netting or similar arrangements. DESC did not have any derivative liabilities at December 31, 2024 which were not subject to master netting or similar arrangements.

Volumes

The following table presents the volume of derivative activity at March 31, 2025. These volumes are based on open derivative positions and represent the combined absolute value of their long and short positions.

Natural Gas (bcf):	Current		Noncurrent
Basis(1)		41		31
Electricity (MWh in millions):
Fixed price		2		22
Interest rate(2) (in millions)		—		71

(1)Includes options.

(2)Maturity is determined based on final settlement period.

Fair Value and Gains and Losses on Derivative Instruments

The following tables present the fair values of derivatives and where they are presented in the Consolidated Balance Sheets:

	Assets		Liabilities
(millions)
At March 31, 2025
Current derivatives not under cash flow hedge accounting
Commodity	$	73	$	—
Interest rate		—		1
Total current derivatives	$	73	$	1
Noncurrent derivatives not under cash flow hedge accounting
Commodity	$	204	$	5
Interest rate		2		1
Total noncurrent derivatives		206		6
Total derivatives	$	279	$	7
At December 31, 2024
Current derivatives not under cash flow hedge accounting
Commodity	$	63	$	—
Total current derivatives	$	63	$	—
Noncurrent derivatives not under cash flow hedge accounting
Commodity	$	307	$	—
Interest rate		2		1
Total noncurrent derivatives		309		1
Total derivatives	$	372	$	1

The following tables present the gains and losses on derivatives, as well as where the associated activity is presented in the Consolidated Balance Sheets and Statements of Comprehensive Income:

Derivatives in Cash Flow Hedging Relationships

(millions)	Increase (Decrease) in Derivatives Subject to Regulatory Treatment(1)(2)
Three Months Ended March 31,	2025		2024
Derivative type and location of gains (losses):
Interest rate	$	—	$	—
Total	$	—	$	—

(1)Represents net derivative activity deferred into and amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/ liabilities have no associated effect in the Consolidated Statements of Comprehensive Income.

(2)All derivatives in cash flow hedging relationships have settled and are being amortized over the life of the debt.

Derivatives Not Designated as Hedging Instruments

(millions)	Amount of Gain (Loss) Recognized in Income on Derivatives(1)
Three Months Ended March 31,	2025			2024
Derivative type and location of gains (losses):
Commodity:
Purchased power	$	3		$	(2	)
Interest rate:
Interest charges		(1	)		(1	)
Total	$	2		$	(3	)

(1)Includes derivative activity amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/liabilities have no associated effect in the Consolidated Statements of Comprehensive Income.

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Fair Value Measurements, Including Derivatives

3 Months Ended

Mar. 31, 2025

Fair Value Disclosures [Abstract]

Fair Value Measurements, Including Derivatives

8. FAIR VALUE MEASUREMENTS, INCLUDING DERIVATIVES

DESC’s fair value measurements are made in accordance with the policies discussed in Note 2 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024. See Note 7 in this report for further information about DESC’s derivatives and hedge accounting activities.

The following table presents DESC’s quantitative information about Level 3 fair value measurements at March 31, 2025. The range and weighted-average are presented in dollars for market price inputs and percentages for price volatility.

	Fair Value (millions)		Valuation Techniques	Unobservable Input		Range	Weighted-average(1)
Assets
Physical forwards:
Electricity	$	199	Discounted cash flow	Market price (per MWh)	(3)	30-83	48
Physical options:
Natural gas(2)		76	Option model	Market price (per Dth)	(3)	3-8	4
				Price volatility	(4)	11%-74%	44%
Total assets	$	275
Liabilities
Physical forwards:
Electricity	$	5	Discounted cash flow	Market price (per MWh)	(3)	30-81	50
Total liabilities	$	5

(1)Averages weighted by volume.

(2)Includes basis.

(3)Represents market prices beyond defined terms for Levels 1 and 2.

(4)Represents volatilities unrepresented in published markets.

Sensitivity of the fair value measurements to changes in the significant unobservable inputs is as follows:

Significant Unobservable Inputs	Position	Change to Input	Impact on Fair Value Measurement
Market price	Buy	Increase (decrease)	Gain (loss)
Market price	Sell	Increase (decrease)	Loss (gain)
Price volatility	Buy	Increase (decrease)	Gain (loss)
Price volatility	Sell	Increase (decrease)	Loss (gain)

Recurring Fair Value Measurements

The following table presents DESC’s assets and liabilities that are measured at fair value on a recurring basis for each hierarchy level, including both current and noncurrent portions:

(millions)	Level 1		Level 2		Level 3		Total
At March 31, 2025
Assets
Derivatives:
Commodity	$	—	$	2	$	275	$	277
Interest rate		—		2		—		2
Investments:
Cash equivalents and other		29		—		—		29
Total assets	$	29	$	4	$	275	$	308
Liabilities
Derivatives:
Commodity	$	—	$	—	$	5	$	5
Interest rate		—		2		—		2
Total liabilities	$	—	$	2	$	5	$	7
At December 31, 2024
Assets
Derivatives:
Commodity	$	—	$	—	$	370	$	370
Interest rate		—		2		—		2
Investments:
Cash equivalents and other		29		—		—		29
Total assets	$	29	$	2	$	370	$	401
Liabilities
Derivatives:
Interest rate	$	—	$	1	$	—	$	1
Total liabilities	$	—	$	1	$	—	$	1

The following table presents the net change in DESC’s assets and liabilities measured at fair value on a recurring basis and included in the Level 3 fair value category.

	Three Months Ended March 31,
	2025			2024
(millions)
Beginning balance	$	370		$	176
Total realized and unrealized gains (losses):
Included in earnings:
Purchased power		3			(2	)
Included in regulatory assets/liabilities		(89	)		70
Settlements		(14	)		2
Purchases		—			7
Ending balance	$	270		$	253

There are no unrealized gains and losses included in earnings in the Level 3 fair value category related to assets/liabilities still held at the reporting date for the three months ended March 31, 2025 and 2024.

Fair Value of Financial Instruments

Substantially all of DESC’s financial instruments are recorded at fair value, with the exception of the instruments described below which are reported at historical cost. Estimated fair values have been determined using available market information and valuation methodologies considered appropriate by management. The carrying amount of financial instruments classified within current assets and current liabilities are representative of fair value because of the short-term nature of these instruments. For financial instruments that are not recorded at fair value, the carrying amounts and estimated fair values are as follows:

	March 31, 2025				December 31, 2024
(millions)	Carrying Amount		Estimated Fair Value(1)		Carrying Amount		Estimated Fair Value(1)
Long-term debt(2)	$	4,666	$	4,632	$	4,220	$	4,142
Affiliated long-term debt		230		230		230		230

(1)Fair value is estimated using market prices, where available, and interest rates currently available for issuance of debt with similar terms and remaining maturities. All fair value measurements are classified as Level 2. The carrying amount of debt issuances with short-term maturities and variable rates refinanced at current market rates is a reasonable estimate of their fair value.

(2)Carrying amount includes current portions, if any, included in securities due within one year and amounts which represent the unamortized debt issuance costs and discount or premium.

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Employee Benefit Plans

3 Months Ended

Mar. 31, 2025

Retirement Benefits [Abstract]

Employee Benefit Plans

9. EMPLOYEE BENEFIT PLANS

In DESC’s Consolidated Statements of Comprehensive Income, the service cost component of net periodic benefit (credit) cost is reflected in other operations and maintenance expense with the non-service cost components reflected in other income (expense). Components of net periodic benefit cost (credit) recorded by DESC were as follows:

(millions)	Pension Benefits						Other Postretirement Benefits
Three Months Ended March 31,	2025			2024			2025			2024
Service cost	$	2		$	2		$	—		$	—
Interest cost		9			8			2			2
Expected return on assets		(10	)		(9	)		—			—
Amortization of actuarial losses		1			2			(1	)		(1	)
Net periodic benefit cost	$	2		$	3		$	1		$	1

During the three months ended March 31, 2025, DESC made less than $1 million of contributions to its qualified pension plan. During the three months ended March 31, 2024, DESC made no contributions to its pension trust. DESC expects to make $3 million of minimum required contributions to its qualified defined benefit pension plans in 2025 and expects to receive reimbursement for such contributions from Santee Cooper. DESC recovers current pension costs through either a rate rider that may be adjusted annually for retail electric operations or through cost of service rates for gas operations.

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Commitments And Contingencies

3 Months Ended

Mar. 31, 2025

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

10. COMMITMENTS AND CONTINGENCIES

As a result of issues generated in the ordinary course of business, DESC is involved in legal proceedings before various courts and is periodically subject to governmental examinations (including by regulatory authorities), inquiries and investigations. Certain legal proceedings and governmental examinations involve demands for unspecified amounts of damages, are in an initial procedural phase, involve uncertainty as to the outcome of pending appeals or motions or involve significant factual issues that need to be resolved, such that it is not possible for DESC to estimate a range of possible loss. For such matters that DESC cannot estimate, a statement to this effect is made in the description of the matter. Other matters may have progressed sufficiently through the litigation or investigative processes such that DESC is able to estimate a range of possible loss. For legal proceedings and governmental examinations that DESC is able to reasonably estimate a range of possible losses, an estimated range of possible loss is provided, in excess of the accrued liability (if any) for such matters. DESC maintains various insurance programs, including general liability insurance coverage which provides coverage for personal injury or wrongful death cases. Any accrued liability is recorded on a gross basis with a receivable also recorded for any probable insurance recoveries. Estimated ranges of loss are inclusive of legal fees and net of any anticipated insurance recoveries. Any estimated range is based on currently available information and involves elements of judgment and significant uncertainties. Any estimated range of possible loss may not represent DESC’s maximum possible loss exposure. The circumstances of such legal proceedings and governmental examinations will change from time to time and actual results may vary significantly from the current estimate. For current proceedings not specifically reported below, management does not anticipate that the liabilities, if any, arising from such proceedings would have a material effect on DESC’s financial position, liquidity or results of operations. During the three months ended March 31, 2025 and 2024, DESC recorded less than $1 million and $6 million, respectively, of charges in aggregate for various personal injury or wrongful death cases. DESC’s Consolidated Balance Sheets at March 31, 2025 and December 31, 2024 include $19 million and $10 million, respectively, of insurance receivables and $16 million and $7 million of reserves, respectively, primarily related to personal injury or wrongful death cases.

Environmental Matters

DESC is subject to costs resulting from a number of federal, state and local laws and regulations designed to protect human health and the environment. These laws and regulations affect future planning and existing operations. They can result in increased capital, operating and other costs as a result of compliance, remediation, containment and monitoring obligations.

From a regulatory perspective, DESC continually monitors and evaluates its current and projected emission levels and strives to comply with all state and federal regulations regarding those emissions. DESC participates in the SO2 and NOx emission allowance programs with respect to coal plant emissions and also has constructed additional pollution control equipment at its coal-fired electric generating plants. These actions are expected to address many of the rules and regulations discussed herein.

Air

The CAA, as amended, is a comprehensive program utilizing a broad range of regulatory tools to protect and preserve the nation’s air quality. At a minimum, states are required to establish regulatory programs to meet applicable requirements of the CAA. However, states may choose to develop regulatory programs that are more restrictive. Many of DESC’s facilities are subject to the CAA’s permitting and other requirements.

Carbon Regulations

In August 2016, the EPA issued a draft rule proposing to reaffirm that a source’s obligation to obtain a PSD or Title V permit for GHGs is triggered only if such permitting requirements are first triggered by non-GHG, or conventional, pollutants that are regulated by the New Source Review program, and exceed a significant emissions rate of 75,000 tons per year of CO2 equivalent emissions. Until the EPA ultimately takes final action on this rulemaking, DESC cannot predict the impact to its results of operations, financial condition and/or cash flows.

Water

The CWA, as amended, is a comprehensive program requiring a broad range of regulatory tools including a permit program to authorize and regulate discharges to surface waters with strong enforcement mechanisms. DESC must comply with applicable aspects of the CWA programs at its operating facilities.

Regulation 316(b)

In October 2014, the final regulations under Section 316(b) of the CWA that govern existing facilities and new units at existing facilities that employ a cooling water intake structure and that have flow levels exceeding a minimum threshold became effective. The rule establishes a national standard for impingement based on seven compliance options, but forgoes the creation of a single technology standard for entrainment. Instead, the EPA has delegated entrainment technology decisions to state regulators. State regulators are to make case-by-case entrainment technology determinations after an examination of five mandatory facility-specific factors, including a social cost-benefit test, and six optional facility-specific factors. The rule governs all electric generating stations with water withdrawals above two MGD, with a heightened entrainment analysis for those facilities over 125 MGD. DESC has five facilities that are subject to the final regulations. DESC is also working with the EPA and state regulatory agencies to assess the applicability of Section 316(b) to five hydroelectric facilities. DESC anticipates that it may have to install impingement control technologies at certain of these stations that have once-through cooling systems. DESC is currently evaluating the need or potential for entrainment controls under the final rule as these decisions will be made on a case-by-case basis after a thorough review of detailed biological, technological and cost benefit studies. DESC is conducting studies and implementing plans as required by the rule to determine appropriate intake structure modifications at certain facilities to ensure compliance with this rule. While the impacts of this rule could be material to DESC’s results of operations, financial condition and/or cash flows, the existing regulatory framework in South Carolina provides rate recovery mechanisms that could substantially mitigate any such impacts for DESC.

Effluent Limitations Guidelines

In September 2015, the EPA released a final rule to revise the ELG Rule. The final rule established updated standards for wastewater discharges that apply primarily at coal and oil steam generating stations. Affected facilities are required to convert from wet to dry or closed cycle coal ash management, improve existing wastewater treatment systems and/or install new wastewater treatment technologies in order to meet the new discharge limits. In April 2017, the EPA granted two separate petitions for reconsideration of the final ELG Rule and stayed future compliance dates in the rule. Also in April 2017, the U.S. Court of Appeals for the Fifth Circuit granted the EPA’s request for a stay of the pending consolidated litigation challenging the rule while the EPA addresses the petitions for reconsideration. In September 2017, the EPA signed a rule to postpone the earliest compliance dates for certain waste streams regulations in the final ELG Rule from November 2018 to November 2020; however, the latest date for compliance for these regulations was December 2023. In October 2020, the EPA released the final rule that extended the latest dates for compliance with individual facilities’ compliance dates that would vary based on circumstances and the determination by state regulators and may range from 2021 to 2028. In May 2024, the EPA released a final rule revising the 2015 and 2020 Effluent Limitations Guidelines, establishing more stringent standards for wastewater discharges for the Steam Electric Power Generating Category, which apply primarily to wastewater discharges at coal and oil steam generating stations. Individual facilities’ compliance dates will vary based on circumstances and the determination by state regulators and may range to 2029, except in certain circumstances when a facility will be retired by 2034. DESC expects to complete wastewater treatment technology retrofits and modifications at the Williams generating station, with a similar project at the Wateree generation station under evaluation, to meet the requirements with the existing regulatory framework in South Carolina providing rate recovery mechanisms for costs of the projects. As discussed below, DESC recorded an increase to its AROs in the second quarter of 2024 in connection with the expected compliance costs associated with the EPA’s May 2024 final rule concerning CCR. DESC expects that such AROs would satisfy any AROs that would have otherwise been necessary for compliance with the EPA’s May 2024 Effluent Limitations Guidelines. DESC is currently unable to estimate what costs, if any, may be required in addition to the project for the Williams generating station, a potential project at the Wateree generating station and the recorded AROs to meet the requirements to operate certain facilities past 2034. However, DESC expects that while such costs for facility improvements, if required, could be material to its financial condition and/or cash flows, the existing regulatory framework in South Carolina provides rate recovery mechanisms that could substantially mitigate any such impacts.

Capacity Use Area

In November 2019, a new CUA was established in the counties surrounding the Cope Generating Station (Western Capacity Use Area) under the South Carolina Groundwater Use and Reporting Regulation. Under the regulation any groundwater well in a CUA that withdraws above three million gallons per month must be permitted. The Cope Generating Station is located within this new Western Capacity Use Area. Cope has been using four deep groundwater wells for cooling water and other house loads since 1996. Prior to designation of the new Western Capacity Use Area, the wells at Cope Station were only required to be registered not permitted. As a result of this designation, Cope will need to restore the surface water equipment to operable status to reduce reliance on groundwater wells. This includes completion of 316(b) requirements, (including SCDES BTA determination and modification of the station national pollutant discharge elimination system permit, which was obtained) and extensive inspection, repair and/or replacement of the associated surface water withdrawal equipment which has been idle since 1996. While the impacts of this rule change are potentially material to DESC’s results of operations, financial condition and/or cash flows, the existing regulatory framework in South Carolina provides rate recovery mechanisms that could substantially mitigate any such impacts for DESC.

Waste Management and Remediation

The operations of DESC are subject to a variety of state and federal laws and regulations governing the management and disposal of solid and hazardous waste, and release of hazardous substances associated with current and/or historical operations. The CERCLA, as amended, and similar state laws, may impose joint, several and strict liability for cleanup on potentially responsible parties who owned, operated or arranged for disposal at facilities affected by a release of hazardous substances. In addition, many states have created programs to incentivize voluntary remediation of sites where historical releases of hazardous substances are identified and property owners or responsible parties decide to initiate cleanups.

From time to time, DESC may be identified as a potentially responsible party in connection with the alleged release of hazardous substances or wastes at a site. Under applicable federal and state laws, DESC could be responsible for costs associated with the investigation or remediation of impacted sites, or subject to contribution claims by other responsible parties for their costs incurred at such sites. DESC also may identify, evaluate and remediate other potentially impacted sites under voluntary state programs. Remediation costs may be subject to reimbursement under DESC’s insurance policies, rate recovery mechanisms, or both. Except as described below, DESC does not believe these matters will have a material effect on results of operations, financial condition and/or cash flows.

DESC has four decommissioned manufactured gas plant sites in South Carolina that are in various states of investigation, remediation and monitoring under work plans approved by, or under review by, the SCDES or the EPA. In the fourth quarter of 2023, DESC completed the majority of remediation activities at one site. DESC anticipates the remaining activities at that site will be completed in 2025 at an estimated cost of less than $1 million, after which the site will continue to incur ongoing maintenance and monitoring obligations. DESC expects to recover costs arising from the remediation work at all four sites through rate recovery mechanisms and as of March 31, 2025, deferred amounts, net of amounts previously recovered through rates and insurance settlements, totaled $33 million and are included in regulatory assets.

Ash Pond and Landfill Closure Costs

In April 2015, the EPA enacted a final rule regulating CCR landfills, existing ash ponds that still receive and manage CCRs and inactive ash ponds that do not receive, but still store, CCRs. DESC currently has inactive and existing CCR ponds and CCR landfills subject to the final rule at three different facilities. This rule created a legal obligation for DESC to retrofit or close all of its inactive and existing ash ponds over a certain period of time, as well as perform required monitoring, corrective action, and post-closure care activities as necessary.

In December 2016, legislation was enacted that creates a framework for EPA-approved state CCR permit programs. In August 2017, the EPA issued interim guidance outlining the framework for state CCR program approval. The EPA has enforcement authority until state programs are approved. The EPA and states with approved programs both will have authority to enforce CCR requirements under their respective rules and programs. In September 2017, the EPA agreed to reconsider portions of the CCR rule in response to two petitions for reconsideration. In March 2018, the EPA proposed certain changes to the CCR rule related to issues remanded as part of the pending litigation and other issues the EPA is reconsidering. Several of the proposed changes would allow states with approved CCR permit programs additional flexibility in implementing their programs. In July 2018, the EPA promulgated the first phase of changes to the CCR rule. In August 2018, the U.S. Court of Appeals for the D.C. Circuit issued its decision in the pending challenges of the CCR rule, vacating and remanding to the EPA three provisions of the rule. In May 2024, the EPA released a final rule to regulate inactive surface impoundments located at retired generating stations that contained CCR and liquids after October 2015, and certain other inactive or previously closed surface impoundments, landfills or other areas that contain accumulations of CCR. DESC believes that it may have inactive or closed units or areas that could be subject to the final rule at up to seven different stations. As discussed in Note 12 to the Consolidated Financial Statements in the Company's Annual Report on Form 10-K for the year ended December 31, 2024, DESC recorded adjustments in its AROs in 2024 in connection with this rule. The actual AROs related to CCRs may vary substantially from the estimates used to record the obligation.

Surety Bonds

At March 31, 2025, DESC had purchased $24 million of surety bonds. Under the terms of surety bonds, DESC is obligated to indemnify the respective surety bond company for any amounts paid.

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Operating Segments

3 Months Ended

Mar. 31, 2025

Segment Reporting [Abstract]

Operating Segments

11. OPERATING SEGMENTS

The Corporate and Other segment primarily includes specific items attributable to DESC’s operating segment that are not included in profit measures evaluated by executive management in assessing the segment’s performance or in allocating resources.

DESC’s CODM is Dominion Energy’s CEO. The CODM uses net income (loss) as the primary profit or loss measure at each segment. The CODM considers budget-to-actual variances on a quarterly basis when making decisions about allocating operating and capital resources to each segment, when assessing the performance of each segment and when determining the compensation of certain employees.

In the three months ended March 31, 2025 and 2024, DESC reported an insignificant amount of specific items in the Corporate and Other segment.

The following table presents segment information pertaining to DESC’s operations:

Three Months Ended March 31,	Dominion Energy South Carolina		Corporate and Other			Consolidated Total
(millions)
2025
Operating Revenue	$	986	$	—		$	986
Fuel used in electric generation(1)		204		—			204
Purchased power(1)		22		—			22
Gas purchased for resale(1)		126		—			126
Other operations and maintenance(1)		174		—			174
Depreciation and amortization(1)		140		—			140
Other taxes(1)		82		—			82
Total Operating Expenses		748		—			748
Other income (expense), net(2)		3		—			3
Interest charges, net of AFUDC(1)		71		—			71
Income tax expense(1)		18		2			20
Comprehensive Income Attributable to Noncontrolling Interest(2)		8		—			8
Comprehensive Income (Loss) Available (Attributable) to    Common Shareholder		144		(2	)		142
Capital expenditures		297		—			297
Total assets (billions)		17.1		—			17.1
2024
Operating Revenue	$	775	$	—		$	775
Fuel used in electric generation(1)		145		—			145
Purchased power(1)		10		—			10
Gas purchased for resale(1)		79		—			79
Other operations and maintenance(1)		163		—			163
Depreciation and amortization(1)		136		—			136
Other taxes(1)		78		—			78
Total Operating Expenses		611		—			611
Other income (expense), net(2)		1		—			1
Interest charges, net of AFUDC(1)		67		—			67
Income tax expense(1)		17		1			18
Comprehensive Income Attributable to Noncontrolling Interest(2)		6		—			6
Comprehensive Income (Loss) Available (Attributable) to    Common Shareholder		75		(1	)		74
Capital expenditures		268		—			268

(1)The significant expense categories and amounts in the segment information presented above align with the segment-level information that is regularly provided to DESC’s CODM.

(2)Items designated are other segment items for each reportable segment.

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Affiliated and Related Party Transactions

3 Months Ended

Mar. 31, 2025

Related Party Transactions [Abstract]

Affiliated and Related Party Transactions

12. AFFILIATED AND RELATED PARTY TRANSACTIONS

DES, on behalf of itself and its parent company, provides the following services to DESC, which are rendered at direct or allocated cost: information systems, telecommunications, customer support, marketing and sales, human resources, corporate compliance, purchasing, financial, risk management, public affairs, legal, investor relations, gas supply and capacity management, strategic planning, general administrative and retirement benefits. Costs for these services include amounts capitalized. Amounts expensed are primarily recorded in other operations and maintenance - affiliated suppliers and other income (expense), net in the Consolidated Statements of Comprehensive Income.

DESC transacts with affiliates for certain quantities of electricity in the ordinary course of business. DESC also enters into certain commodity derivative contracts with affiliates. DESC uses these contracts, which are principally comprised of forward commodity purchases, to manage commodity price risks associated with purchases of electricity. See Note 7 for additional information.

	Three Months Ended March 31,
(millions)	2025		2024
Direct and allocated costs from DES(1)	$	62	$	53
Operating Revenues - Electric from sales to affiliate		1		1
Operating Expenses - Other taxes from affiliate		3		3
Purchases of electricity from solar affiliates		3		1

(1)Includes capitalized expenditures of $19 million and $12 million for the three months ended March 31, 2025 and 2024, respectively.

(millions)	March 31, 2025		December 31, 2024
Payable to DES	$	19	$	19
Payable to SCANA Corporation		7		7
Derivative assets with affiliates(1)		33		48

(1)Includes amounts recorded in current derivative assets of $6 million and $4 million as of March 31, 2025 and December 31, 2024, respectively, and amounts recorded in noncurrent derivative assets of $27 million and $44 million as of March 31, 2025 and December 31, 2024, respectively.

Borrowings from an affiliate are described in Note 5.

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Other Income (Expense), Net

3 Months Ended

Mar. 31, 2025

Income Statement [Abstract]

Other Income (Expense), Net

13. OTHER INCOME (EXPENSE), NET

Components of other income (expense), net are as follows:

	Three Months Ended March 31,
(millions)	2025			2024
Other income	$	5		$	2
Gains on sales of assets		—			1
Other expense		(2	)		(5	)
Allowance for equity funds used during construction		—			3
Other income (expense), net	$	3		$	1

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Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2025

Accounting Policies [Abstract]

Basis of Consolidation and Variable Interest Entities

Basis of Consolidation and Variable Interest Entities

DESC has determined that it has a controlling financial interest in each of GENCO and Fuel Company (which are considered to be VIEs) and, accordingly, DESC’s Consolidated Financial Statements include, after eliminating intercompany balances and transactions, the accounts of DESC, GENCO and Fuel Company. See Note 2 to the Consolidated Financial Statements included in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024 for a description of GENCO and Fuel Company.

DESC purchases shared services from DES, an affiliated VIE that provides accounting, legal, finance and certain administrative and technical services to all Dominion Energy subsidiaries, including DESC. DESC has determined that it is not the primary beneficiary of DES as it does not have either the power to direct the activities that most significantly impact its economic performance or an obligation to absorb losses and benefits which could be significant to it. See Note 12 for amounts attributable to affiliates.

Significant Accounting Policies

There have been no significant changes from Note 2 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2024.

Regulatory Matters Involving Potential Loss Contingencies

Regulatory Matters Involving Potential Loss Contingencies

As a result of issues generated in the ordinary course of business, DESC is involved in various regulatory matters. Certain regulatory matters may ultimately result in a loss; however, as such matters are in an initial procedural phase, involve uncertainty as to the outcome of pending reviews or orders, and/or involve significant factual issues that need to be resolved, it is not possible for DESC to estimate a range of possible loss. For regulatory matters that DESC cannot estimate, a statement to this effect is made in the description of the matter. Other matters may have progressed sufficiently through the regulatory process such that DESC is able to estimate a range of possible loss. For regulatory matters that DESC is able to reasonably estimate a range of possible losses, an estimated range of possible loss is provided, in excess of the accrued liability (if any) for such matters. Any estimated range is based on currently available information, involves elements of judgment and significant uncertainties and may not represent DESC’s maximum possible loss exposure. The circumstances of such regulatory matters will change from time to time and actual results may vary significantly from the current estimate. For current matters not specifically reported below, management does not anticipate that the outcome from such matters would have a material effect on DESC’s financial position, liquidity or results of operations.

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Rate and Other Regulatory Matters (Tables)

3 Months Ended

Mar. 31, 2025

Regulated Operations [Abstract]

Schedule of Regulatory Assets and Liabilities

	March 31,		December 31,
(millions)	2025		2024
Regulatory assets:
NND Project costs(1)	$	138	$	138
AROs(2)		6		8
Deferred employee benefit plan costs(3)		5		8
Other unrecovered plant(4)		18		18
DSM programs(5)		23		24
Cost of fuel and purchased gas under-collections(6)		92		35
Other		58		68
Regulatory assets - current		340		299
NND Project costs(1)		1,776		1,811
AROs(2)		704		695
Deferred employee benefit plan costs(3)		96		94
Interest rate hedges(7)		167		167
Other unrecovered plant(4)		94		89
DSM programs(5)		48		49
Environmental remediation costs(8)		42		42
Deferred storm damage costs(9)		77		76
Deferred transmission operating costs(10)		71		72
Derivatives(11)		94		95
Other(12)		193		152
Regulatory assets - noncurrent		3,362		3,342
Total regulatory assets	$	3,702	$	3,641
Regulatory liabilities:
Monetization of guaranty settlement(13)	$	67	$	67
Income taxes refundable through future rates(14)		17		24
Reserve for refunds to electric utility customers(15)		67		73
Derivatives(11)		44		27
Other		32		10
Regulatory liabilities - current		227		201
Monetization of guaranty settlement(13)		552		568
Income taxes refundable through future rates(14)		838		820
Asset removal costs(16)		597		598
Reserve for refunds to electric utility customers(15)		146		161
Derivatives(11)		223		328
Other		5		13
Regulatory liabilities - noncurrent		2,361		2,488
Total regulatory liabilities	$	2,588	$	2,689

(1)Reflects expenditures associated with the NND Project, which pursuant to the SCANA Merger Approval Order, will be recovered from electric service customers over a 20-year period ending in 2039.

(2)Represents uncollected costs, including deferred depreciation and accretion expense, related to legal obligations associated with the future retirement of generation, transmission and distribution properties. The AROs primarily relate to DESC’s electric generating facilities, including Summer, and are expected to be recovered over the related property lives and periods of decommissioning which may range up to approximately 105 years. In addition, the balance reflects amounts related to the EPA’s May 2024 final rule concerning CCR as discussed in Note 10.

(3)Employee benefit plan costs have historically been recovered as they have been recorded under GAAP. Deferred employee benefit plan costs represent amounts of pension and other postretirement benefit costs which were accrued as liabilities and treated as regulatory assets pursuant to FERC guidance, and costs deferred pursuant to specific South Carolina Commission regulatory orders. Based on rates currently in effect, DESC expects to recover certain deferred benefit costs through utility rates over average service periods of participating employees, which is approximately 11 years. DESC expects to recover other deferred pension costs through utility rates over periods through 2044.

(4)Represents the carrying value of coal-fired generating units, including related materials and supplies inventory, retired from service prior to being fully depreciated. DESC is amortizing these amounts through cost of service rates following depreciation amounts that were designed to recover the retired units cost over their previous estimated remaining useful lives, which has been estimated to be through 2025. Based on current projections of remaining decommissioning costs, projected recovery is expected to extend through 2039. In addition, amounts include unrecovered costs of existing meters and equipment retired from service prior to being fully depreciated as part of the Advanced Metering Infrastructure project, which are being recovered through rates through 2028. This amount also includes certain inventory and preliminary survey and investigation charges being amortized through 2026 related to the transition or conversion from coal to gas fired generation at certain facilities. The majority of unamortized amounts are included in rate base and are earning a current return.

(5)Primarily represents deferred costs associated with electric demand reduction programs, and such deferred costs are currently being recovered over three years through an approved rate rider.

(6)Represents amounts under- or over-collected from customers pursuant to the cost of fuel and purchased gas components approved by the South Carolina Commission.

(7)Represents settled interest rate derivatives designated as cash flow hedges expected to be amortized to interest expense over the lives of the underlying debt through 2065.

(8)Reflects amounts associated with the assessment and clean-up of sites currently or formerly owned by DESC. Such remediation costs are expected to be recovered over periods of up to 24 years. See Note 10 for additional information.

(9)Represents storm restoration costs for which DESC expects to receive future recovery. Pursuant to the settlement agreement approved in DESC’s retail electric base rate case in August 2024, for costs incurred prior to September 2024, DESC expects to receive future recovery through customer rates through 2034 and for costs incurred effective September 2024, DESC expects to receive future recovery through customer rates of approximately $2 million each year. Unamortized amounts are included in rate base and are earning a current return.

(10)Includes deferred depreciation and property taxes associated with certain transmission assets for which DESC expects future recovery from customers through 2062. Unamortized amounts are included in rate base and earning a current return.

(11)Represents changes in the fair value of derivatives, excluding separately presented interest rate hedges, that following settlement are expected to be recovered from or refunded to customers.

(12)Various other regulatory assets are expected to be recovered through rates over varying periods through 2078.

(13)Represents proceeds related to the monetization of the Toshiba Settlement. In accordance with the SCANA Merger Approval Order, this balance, net of amounts that may be required to satisfy liens, will be refunded to electric customers over a 20-year period ending in 2039.

(14)Includes (i) excess deferred income taxes arising from the remeasurement of deferred income taxes in connection with the enactment of the 2017 Tax Reform Act (certain of which are protected under normalization rules and will be amortized over the remaining lives of related property, and certain of which will be amortized to the benefit of customers over prescribed periods as instructed by regulators) and (ii) deferred income taxes arising from investment tax credits, offset by (iii) deferred income taxes that arise from utility operations that have not been included in customer rates (a portion of which relate to depreciation and are expected to be recovered over the remaining lives of the related property which may range up to 85 years).

(15)Reflects amounts previously collected from retail electric customers of DESC for the NND Project to be credited to customers over an estimated 11-year period effective February 2019 in connection with the SCANA Merger Approval Order.

(16)Represents estimated net collections through depreciation rates of amounts to be expended for the removal of assets in the future.

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Operating Revenue (Tables)

3 Months Ended

Mar. 31, 2025

Revenue Recognition and Deferred Revenue [Abstract]

Disaggregation of Revenue

DESC’s revenue consists of the following:

Three Months Ended March 31,	2025				2024
(millions)	Electric		Gas		Electric		Gas
Customer class:
Residential	$	371	$	151	$	283	$	117
Commercial		228		54		188		41
Industrial		109		27		87		18
Other		32		8		28		6
Revenues from contracts with customers		740		240		586		182
Other revenues		6		—		7		—
Total Operating Revenues	$	746	$	240	$	593	$	182

Balance and Activity Related to Contract Costs Deferred as Regulatory Assets

Balances and activity related to contract costs deferred as regulatory assets were as follows:

	Regulatory Assets
(millions)	March 31, 2025		December 31, 2024
Beginning balance	$	10	$	11
Additional costs		4		—
Amortization		—		(1	)
Ending balance	$	14	$	10

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Long-Term and Short-Term Debt (Tables)

3 Months Ended

Mar. 31, 2025

Debt Disclosure [Abstract]

Schedule of Line of Credit Facilities

At March 31, 2025, DESC’s share of commercial paper and letters of credit outstanding under its joint credit facility with Dominion Energy was as follows:

(millions)	Maximum Facility Sub-Limit		Outstanding Commercial Paper		Outstanding Letters of Credit
Joint revolving credit facility(1)	$	1,000	$	210	$	—

(1)A maximum of $1.0 billion of the facility is available to DESC, assuming adequate capacity is available after giving effect to uses by co-borrowers Dominion Energy and Virginia Power. A sub-limit for DESC is set within the facility limit but can be changed at the option of the co-borrowers multiple times per year. At March 31, 2025, the sub-limit for DESC was $500 million. In April 2025, the sub-limit was increased up to $1.0 billion. If DESC has liquidity needs in excess of its sub-limit, the sub-limit may be changed provided that it does not exceed $1.0 billion or such needs may be satisfied through short-term borrowings from Dominion Energy. This credit facility, as amended in April 2025, matures in April 2030, with the potential to be extended by the borrowers to April 2032. The credit facility can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $3.0 billion (or the sub-limit, whichever is less) of letters of credit.

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Income Taxes (Tables)

3 Months Ended

Mar. 31, 2025

Income Tax Disclosure [Abstract]

Schedule of Effective Income Tax Rate Reconciliation

Three Months Ended March 31,	2025			2024
U.S. statutory rate		21.0	%		21.0	%
Increases (reductions) resulting from:
State taxes, net of federal benefit		10.8			3.9
Reversal of excess deferred income taxes		(2.4	)		(5.3	)
Allowance for equity funds used during construction		—			(0.7	)
Remeasurements and settlements of uncertain tax positions		(17.5	)	—
Other, net		(0.2	)	—
Effective tax rate		11.7	%		18.9	%

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Derivative Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2025

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Offsetting Assets

The table below presents derivative balances by type of financial instrument, if the gross amounts recognized in the Consolidated Balance Sheets were netted with derivative instruments and cash collateral received or paid:

	March 31, 2025								December 31, 2024
	Gross Amounts Not Offset in the Consolidated Balance Sheet								Gross Amounts Not Offset in the Consolidated Balance Sheet
(millions)	Gross Assets Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Received		Net Amounts		Gross Assets Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Received		Net Amounts
Interest rate contracts:
Over-the-counter	$	2	$	—	$	—	$	2	$	2	$	—	$	—	$	2
Commodity contracts:
Over-the-counter	$	78	$	—	$	—	$	78	$	81	$	—	$	—	$	81
Total derivatives	$	80	$	—	$	—	$	80	$	83	$	—	$	—	$	83

(1)Excludes derivative assets of $199 million and $289 million at March 31, 2025 and December 31, 2024, respectively, which are not subject to master netting or similar arrangements.

Offsetting Liabilities

	March 31, 2025								December 31, 2024
	Gross Amounts Not Offset in the Consolidated Balance Sheet								Gross Amounts Not Offset in the Consolidated Balance Sheet
(millions)	Gross Liabilities Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Paid		Net Amounts		Gross Liabilities Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Paid		Net Amounts
Interest rate contracts:
Over-the-counter	$	2	$	—	$	—	$	2	$	1	$	—	$	—	$	1
Total derivatives	$	2	$	—	$	—	$	2	$	1	$	—	$	—	$	1

(1)Excludes derivative liabilities of $5 million at March 31, 2025, which are not subject to master netting or similar arrangements. DESC did not have any derivative liabilities at December 31, 2024 which were not subject to master netting or similar arrangements.

Schedule of Volume of Derivative Activity

The following table presents the volume of derivative activity at March 31, 2025. These volumes are based on open derivative positions and represent the combined absolute value of their long and short positions.

Natural Gas (bcf):	Current		Noncurrent
Basis(1)		41		31
Electricity (MWh in millions):
Fixed price		2		22
Interest rate(2) (in millions)		—		71

(1)Includes options.

(2)Maturity is determined based on final settlement period.

Fair Value of Derivatives

The following tables present the fair values of derivatives and where they are presented in the Consolidated Balance Sheets:

	Assets		Liabilities
(millions)
At March 31, 2025
Current derivatives not under cash flow hedge accounting
Commodity	$	73	$	—
Interest rate		—		1
Total current derivatives	$	73	$	1
Noncurrent derivatives not under cash flow hedge accounting
Commodity	$	204	$	5
Interest rate		2		1
Total noncurrent derivatives		206		6
Total derivatives	$	279	$	7
At December 31, 2024
Current derivatives not under cash flow hedge accounting
Commodity	$	63	$	—
Total current derivatives	$	63	$	—
Noncurrent derivatives not under cash flow hedge accounting
Commodity	$	307	$	—
Interest rate		2		1
Total noncurrent derivatives		309		1
Total derivatives	$	372	$	1

Derivatives in Cash Flow Hedging Relationships

The following tables present the gains and losses on derivatives, as well as where the associated activity is presented in the Consolidated Balance Sheets and Statements of Comprehensive Income:

Derivatives in Cash Flow Hedging Relationships

(millions)	Increase (Decrease) in Derivatives Subject to Regulatory Treatment(1)(2)
Three Months Ended March 31,	2025		2024
Derivative type and location of gains (losses):
Interest rate	$	—	$	—
Total	$	—	$	—

(1)Represents net derivative activity deferred into and amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/ liabilities have no associated effect in the Consolidated Statements of Comprehensive Income.

(2)All derivatives in cash flow hedging relationships have settled and are being amortized over the life of the debt.

Derivatives Not Designated as Hedging Instruments

Derivatives Not Designated as Hedging Instruments

(millions)	Amount of Gain (Loss) Recognized in Income on Derivatives(1)
Three Months Ended March 31,	2025			2024
Derivative type and location of gains (losses):
Commodity:
Purchased power	$	3		$	(2	)
Interest rate:
Interest charges		(1	)		(1	)
Total	$	2		$	(3	)

(1)Includes derivative activity amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/liabilities have no associated effect in the Consolidated Statements of Comprehensive Income.

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Fair Value Measurements, Including Derivatives (Tables)

3 Months Ended

Mar. 31, 2025

Fair Value Disclosures [Abstract]

Schedule of Quantitative Information About Level 3 Fair Value Measurements

The following table presents DESC’s quantitative information about Level 3 fair value measurements at March 31, 2025. The range and weighted-average are presented in dollars for market price inputs and percentages for price volatility.

	Fair Value (millions)		Valuation Techniques	Unobservable Input		Range	Weighted-average(1)
Assets
Physical forwards:
Electricity	$	199	Discounted cash flow	Market price (per MWh)	(3)	30-83	48
Physical options:
Natural gas(2)		76	Option model	Market price (per Dth)	(3)	3-8	4
				Price volatility	(4)	11%-74%	44%
Total assets	$	275
Liabilities
Physical forwards:
Electricity	$	5	Discounted cash flow	Market price (per MWh)	(3)	30-81	50
Total liabilities	$	5

(1)Averages weighted by volume.

(2)Includes basis.

(3)Represents market prices beyond defined terms for Levels 1 and 2.

(4)Represents volatilities unrepresented in published markets.

Schedule of Sensitivity of The Fair Value Measurements To Changes in The Significant Unobservable Inputs

Sensitivity of the fair value measurements to changes in the significant unobservable inputs is as follows:

Significant Unobservable Inputs	Position	Change to Input	Impact on Fair Value Measurement
Market price	Buy	Increase (decrease)	Gain (loss)
Market price	Sell	Increase (decrease)	Loss (gain)
Price volatility	Buy	Increase (decrease)	Gain (loss)
Price volatility	Sell	Increase (decrease)	Loss (gain)

Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis

The following table presents DESC’s assets and liabilities that are measured at fair value on a recurring basis for each hierarchy level, including both current and noncurrent portions:

(millions)	Level 1		Level 2		Level 3		Total
At March 31, 2025
Assets
Derivatives:
Commodity	$	—	$	2	$	275	$	277
Interest rate		—		2		—		2
Investments:
Cash equivalents and other		29		—		—		29
Total assets	$	29	$	4	$	275	$	308
Liabilities
Derivatives:
Commodity	$	—	$	—	$	5	$	5
Interest rate		—		2		—		2
Total liabilities	$	—	$	2	$	5	$	7
At December 31, 2024
Assets
Derivatives:
Commodity	$	—	$	—	$	370	$	370
Interest rate		—		2		—		2
Investments:
Cash equivalents and other		29		—		—		29
Total assets	$	29	$	2	$	370	$	401
Liabilities
Derivatives:
Interest rate	$	—	$	1	$	—	$	1
Total liabilities	$	—	$	1	$	—	$	1

Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis and included in Level 3

The following table presents the net change in DESC’s assets and liabilities measured at fair value on a recurring basis and included in the Level 3 fair value category.

	Three Months Ended March 31,
	2025			2024
(millions)
Beginning balance	$	370		$	176
Total realized and unrealized gains (losses):
Included in earnings:
Purchased power		3			(2	)
Included in regulatory assets/liabilities		(89	)		70
Settlements		(14	)		2
Purchases		—			7
Ending balance	$	270		$	253

Schedule of Carrying Values and Estimated Fair Values of Debt Instruments

For financial instruments that are not recorded at fair value, the carrying amounts and estimated fair values are as follows:

	March 31, 2025				December 31, 2024
(millions)	Carrying Amount		Estimated Fair Value(1)		Carrying Amount		Estimated Fair Value(1)
Long-term debt(2)	$	4,666	$	4,632	$	4,220	$	4,142
Affiliated long-term debt		230		230		230		230

(1)Fair value is estimated using market prices, where available, and interest rates currently available for issuance of debt with similar terms and remaining maturities. All fair value measurements are classified as Level 2. The carrying amount of debt issuances with short-term maturities and variable rates refinanced at current market rates is a reasonable estimate of their fair value.

(2)Carrying amount includes current portions, if any, included in securities due within one year and amounts which represent the unamortized debt issuance costs and discount or premium.

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Employee Benefit Plans (Tables)

3 Months Ended

Mar. 31, 2025

Retirement Benefits [Abstract]

Components of Net Periodic Benefit Cost (Credit)

Components of net periodic benefit cost (credit) recorded by DESC were as follows:

(millions)	Pension Benefits						Other Postretirement Benefits
Three Months Ended March 31,	2025			2024			2025			2024
Service cost	$	2		$	2		$	—		$	—
Interest cost		9			8			2			2
Expected return on assets		(10	)		(9	)		—			—
Amortization of actuarial losses		1			2			(1	)		(1	)
Net periodic benefit cost	$	2		$	3		$	1		$	1

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Operating Segments (Tables)

3 Months Ended

Mar. 31, 2025

Segment Reporting [Abstract]

Schedule of Segment Reporting Information, by Segment

The following table presents segment information pertaining to DESC’s operations:

Three Months Ended March 31,	Dominion Energy South Carolina		Corporate and Other			Consolidated Total
(millions)
2025
Operating Revenue	$	986	$	—		$	986
Fuel used in electric generation(1)		204		—			204
Purchased power(1)		22		—			22
Gas purchased for resale(1)		126		—			126
Other operations and maintenance(1)		174		—			174
Depreciation and amortization(1)		140		—			140
Other taxes(1)		82		—			82
Total Operating Expenses		748		—			748
Other income (expense), net(2)		3		—			3
Interest charges, net of AFUDC(1)		71		—			71
Income tax expense(1)		18		2			20
Comprehensive Income Attributable to Noncontrolling Interest(2)		8		—			8
Comprehensive Income (Loss) Available (Attributable) to    Common Shareholder		144		(2	)		142
Capital expenditures		297		—			297
Total assets (billions)		17.1		—			17.1
2024
Operating Revenue	$	775	$	—		$	775
Fuel used in electric generation(1)		145		—			145
Purchased power(1)		10		—			10
Gas purchased for resale(1)		79		—			79
Other operations and maintenance(1)		163		—			163
Depreciation and amortization(1)		136		—			136
Other taxes(1)		78		—			78
Total Operating Expenses		611		—			611
Other income (expense), net(2)		1		—			1
Interest charges, net of AFUDC(1)		67		—			67
Income tax expense(1)		17		1			18
Comprehensive Income Attributable to Noncontrolling Interest(2)		6		—			6
Comprehensive Income (Loss) Available (Attributable) to    Common Shareholder		75		(1	)		74
Capital expenditures		268		—			268

(1)The significant expense categories and amounts in the segment information presented above align with the segment-level information that is regularly provided to DESC’s CODM.

(2)Items designated are other segment items for each reportable segment.

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Affiliated and Related Party Transactions (Tables)

3 Months Ended

Mar. 31, 2025

Related Party Transactions [Abstract]

Schedule of Affiliated Transactions

Amounts expensed are primarily recorded in other operations and maintenance - affiliated suppliers and other income (expense), net in the Consolidated Statements of Comprehensive Income.

	Three Months Ended March 31,
(millions)	2025		2024
Direct and allocated costs from DES(1)	$	62	$	53
Operating Revenues - Electric from sales to affiliate		1		1
Operating Expenses - Other taxes from affiliate		3		3
Purchases of electricity from solar affiliates		3		1

(1)Includes capitalized expenditures of $19 million and $12 million for the three months ended March 31, 2025 and 2024, respectively.

Schedule of Affiliated Transactions

(millions)	March 31, 2025		December 31, 2024
Payable to DES	$	19	$	19
Payable to SCANA Corporation		7		7
Derivative assets with affiliates(1)		33		48

(1)Includes amounts recorded in current derivative assets of $6 million and $4 million as of March 31, 2025 and December 31, 2024, respectively, and amounts recorded in noncurrent derivative assets of $27 million and $44 million as of March 31, 2025 and December 31, 2024, respectively.

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Other Income (Expense), Net (Tables)

3 Months Ended

Mar. 31, 2025

Income Statement [Abstract]

Components of Other Income (Expense), Net

Components of other income (expense), net are as follows:

	Three Months Ended March 31,
(millions)	2025			2024
Other income	$	5		$	2
Gains on sales of assets		—			1
Other expense		(2	)		(5	)
Allowance for equity funds used during construction		—			3
Other income (expense), net	$	3		$	1

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Rate and Other Regulatory Matters (Narrative) (Detail) $ in Millions	1 Months Ended				3 Months Ended
	Feb. 28, 2025 USD ($)	Jan. 31, 2025 USD ($)	Dec. 31, 2024 USD ($) mi kV	Sep. 30, 2024 USD ($)	Mar. 31, 2025	Feb. 27, 2025 USD ($)
Rate And Other Regulatory Matters [Line Items]
Miles of Lines | mi			17
Type of Line | kV			230
Estimated electric transmission project cost			$ 55
Regulatory asset recovery assessment end period					2078
Dominion Energy South Carolina, Inc. [Member]
Rate And Other Regulatory Matters [Line Items]
Storm restoration expected recovery period					2034
Storm restoration expected recovery				$ 2
Electric - Cost of Fuel [Member]
Rate And Other Regulatory Matters [Line Items]
Proposed South Carolina Commission Order for Increase of Total Fuel Cost Component of Retail Electric Rates to produce a projected under-recovery						$ 154
Reserve For Refunds To Electric Utility Customers [Member]
Rate And Other Regulatory Matters [Line Items]
Electric service customers recovery period					11 years
Deferred Losses or Gains On Interest Rate Derivatives [Member]
Rate And Other Regulatory Matters [Line Items]
Changes in fair value and payments of interest rate derivatives designated as cash flow hedge, amortized to interest expense, year					2065
Monetization Of Guaranty Settlement [Member]
Rate And Other Regulatory Matters [Line Items]
Electric service customers recovery period					20 years
End period for recovery					Dec. 31, 2039
Income Taxes Refundable Through Future Rates [Member]
Rate And Other Regulatory Matters [Line Items]
Remaining lives of related property period					85 years
NND Project Costs [Member]
Rate And Other Regulatory Matters [Line Items]
Electric service customers recovery period					20 years
End period for recovery					Dec. 31, 2039
Deferred Employee Benefit Plan Costs [Member]
Rate And Other Regulatory Matters [Line Items]
Regulatory asset recovery assessment end period					2044
Average service period expected to recover other deferred benefit costs					11 years
Other Unrecovered Plant [Member]
Rate And Other Regulatory Matters [Line Items]
Amortization of carrying value of coal-fired generating unit					2025
New expected amortization of carrying value of coal-fired generating unit					2039
Advanced Metering Infrastructure Project [Member]
Rate And Other Regulatory Matters [Line Items]
New expected amortization of carrying value of coal-fired generating unit					2028
Demand Side Management Programs [Member]
Rate And Other Regulatory Matters [Line Items]
Recovery period of regulatory asset					3 years
Asset Retirement Obligation Costs [Member]
Rate And Other Regulatory Matters [Line Items]
Recovery period of regulatory asset					105 years
Environmental Remediation Costs [Member]
Rate And Other Regulatory Matters [Line Items]
Recovery period of regulatory asset					24 years
Deferred Transmission Operating Costs [Member]
Rate And Other Regulatory Matters [Line Items]
Deferred transmission operating costs expected recovery period					2062
Rider D S M [Member] | Electric - Other [Member]
Rate And Other Regulatory Matters [Line Items]
South Carolina Commission Order, Annual DSM Program Rate Rider Recovery Amount		$ 46
South Carolina Commission [Member] | Electric - Other [Member]
Rate And Other Regulatory Matters [Line Items]
Annual increase (decrease) in pension cost rider	$ 13

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Rate and Other Regulatory Matters (Schedule of Regulatory Assets) (Detail) - USD ($) $ in Millions		Mar. 31, 2025	Dec. 31, 2024
Regulatory Assets
Regulatory assets, current		$ 340	$ 299
Regulatory assets, noncurrent		3,362	3,342
Total regulatory assets		3,702	3,641
NND Project Costs [Member]
Regulatory Assets
Regulatory assets, current	[1]	138	138
Regulatory assets, noncurrent	[1]	1,776	1,811
Asset Retirement Obligation Costs [Member]
Regulatory Assets
Regulatory assets, current	[2]	6	8
Regulatory assets, noncurrent	[2]	704	695
Deferred Employee Benefit Plan Costs [Member]
Regulatory Assets
Regulatory assets, current	[3]	5	8
Regulatory assets, noncurrent	[3]	96	94
Interest Rate Hedges [Member]
Regulatory Assets
Regulatory assets, noncurrent	[4]	167	167
Other Unrecovered Plant [Member]
Regulatory Assets
Regulatory assets, current	[5]	18	18
Regulatory assets, noncurrent	[5]	94	89
Demand Side Management Programs [Member]
Regulatory Assets
Regulatory assets, current	[6]	23	24
Regulatory assets, noncurrent	[6]	48	49
Cost of Fuel and Purchased Gas Under-Collections [Member]
Regulatory Assets
Regulatory assets, current	[7]	92	35
Environmental Remediation Costs [Member]
Regulatory Assets
Regulatory assets, noncurrent	[8]	42	42
Deferred Storm Damage Costs [Member]
Regulatory Assets
Regulatory assets, noncurrent	[9]	77	76
Deferred Transmission Operating Costs [Member]
Regulatory Assets
Regulatory assets, noncurrent	[10]	71	72
Derivatives [Member]
Regulatory Assets
Regulatory assets, noncurrent	[11]	94	95
Other Regulatory Assets [Member]
Regulatory Assets
Regulatory assets, current		58	68
Regulatory assets, noncurrent	[12]	$ 193	$ 152

[1] Reflects expenditures associated with the NND Project, which pursuant to the SCANA Merger Approval Order, will be recovered from electric service customers over a 20-year period ending in 2039.

[2] Represents uncollected costs, including deferred depreciation and accretion expense, related to legal obligations associated with the future retirement of generation, transmission and distribution properties. The AROs primarily relate to DESC’s electric generating facilities, including Summer, and are expected to be recovered over the related property lives and periods of decommissioning which may range up to approximately 105 years. In addition, the balance reflects amounts related to the EPA’s May 2024 final rule concerning CCR as discussed in Note 10.

[3] Employee benefit plan costs have historically been recovered as they have been recorded under GAAP. Deferred employee benefit plan costs represent amounts of pension and other postretirement benefit costs which were accrued as liabilities and treated as regulatory assets pursuant to FERC guidance, and costs deferred pursuant to specific South Carolina Commission regulatory orders. Based on rates currently in effect, DESC expects to recover certain deferred benefit costs through utility rates over average service periods of participating employees, which is approximately 11 years. DESC expects to recover other deferred pension costs through utility rates over periods through 2044.

[4] Represents settled interest rate derivatives designated as cash flow hedges expected to be amortized to interest expense over the lives of the underlying debt through 2065.

[5] Represents the carrying value of coal-fired generating units, including related materials and supplies inventory, retired from service prior to being fully depreciated. DESC is amortizing these amounts through cost of service rates following depreciation amounts that were designed to recover the retired units cost over their previous estimated remaining useful lives, which has been estimated to be through 2025. Based on current projections of remaining decommissioning costs, projected recovery is expected to extend through 2039. In addition, amounts include unrecovered costs of existing meters and equipment retired from service prior to being fully depreciated as part of the Advanced Metering Infrastructure project, which are being recovered through rates through 2028. This amount also includes certain inventory and preliminary survey and investigation charges being amortized through 2026 related to the transition or conversion from coal to gas fired generation at certain facilities. The majority of unamortized amounts are included in rate base and are earning a current return.

[6] Primarily represents deferred costs associated with electric demand reduction programs, and such deferred costs are currently being recovered over three years through an approved rate rider.

[7] Represents amounts under- or over-collected from customers pursuant to the cost of fuel and purchased gas components approved by the South Carolina Commission.

[8] Reflects amounts associated with the assessment and clean-up of sites currently or formerly owned by DESC. Such remediation costs are expected to be recovered over periods of up to 24 years. See Note 10 for additional information.

[9] Represents storm restoration costs for which DESC expects to receive future recovery. Pursuant to the settlement agreement approved in DESC’s retail electric base rate case in August 2024, for costs incurred prior to September 2024, DESC expects to receive future recovery through customer rates through 2034 and for costs incurred effective September 2024, DESC expects to receive future recovery through customer rates of approximately $2 million each year. Unamortized amounts are included in rate base and are earning a current return.

[10] Includes deferred depreciation and property taxes associated with certain transmission assets for which DESC expects future recovery from customers through 2062. Unamortized amounts are included in rate base and earning a current return.

[11] Represents changes in the fair value of derivatives, excluding separately presented interest rate hedges, that following settlement are expected to be recovered from or refunded to customers.

[12] Various other regulatory assets are expected to be recovered through rates over varying periods through 2078.

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Rate and Other Regulatory Matters (Schedule of Regulatory Liabilities) (Detail) - USD ($) $ in Millions		Mar. 31, 2025	Dec. 31, 2024
Regulatory Liabilities
Regulatory liability, current		$ 227	$ 201
Regulatory liability, noncurrent		2,361	2,488
Total regulatory liabilities		2,588	2,689
Monetization Of Guaranty Settlement [Member]
Regulatory Liabilities
Regulatory liability, current	[1]	67	67
Regulatory liability, noncurrent	[1]	552	568
Income Taxes Refundable Through Future Rates [Member]
Regulatory Liabilities
Regulatory liability, current	[2]	17	24
Regulatory liability, noncurrent	[2]	838	820
Asset Removal Costs [Member]
Regulatory Liabilities
Regulatory liability, noncurrent	[3]	597	598
Reserve For Refunds To Electric Utility Customers [Member]
Regulatory Liabilities
Regulatory liability, current	[4]	67	73
Regulatory liability, noncurrent	[4]	146	161
Derivatives [Member]
Regulatory Liabilities
Regulatory liability, current	[5]	44	27
Regulatory liability, noncurrent	[5]	223	328
Other Regulatory Liability [Member]
Regulatory Liabilities
Regulatory liability, current		32	10
Regulatory liability, noncurrent		$ 5	$ 13

[1] Represents proceeds related to the monetization of the Toshiba Settlement. In accordance with the SCANA Merger Approval Order, this balance, net of amounts that may be required to satisfy liens, will be refunded to electric customers over a 20-year period ending in 2039.

[2] Includes (i) excess deferred income taxes arising from the remeasurement of deferred income taxes in connection with the enactment of the 2017 Tax Reform Act (certain of which are protected under normalization rules and will be amortized over the remaining lives of related property, and certain of which will be amortized to the benefit of customers over prescribed periods as instructed by regulators) and (ii) deferred income taxes arising from investment tax credits, offset by (iii) deferred income taxes that arise from utility operations that have not been included in customer rates (a portion of which relate to depreciation and are expected to be recovered over the remaining lives of the related property which may range up to 85 years).

[3] Represents estimated net collections through depreciation rates of amounts to be expended for the removal of assets in the future.

[4] Reflects amounts previously collected from retail electric customers of DESC for the NND Project to be credited to customers over an estimated 11-year period effective February 2019 in connection with the SCANA Merger Approval Order.

[5] Represents changes in the fair value of derivatives, excluding separately presented interest rate hedges, that following settlement are expected to be recovered from or refunded to customers.

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Operating Revenue (Disaggregation of Revenue) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2025	Mar. 31, 2024
Total Operating Revenues	[1]	$ 986	$ 775
Electric Operations
Operating revenue from contracts with customers		740	586
Other revenues		6	7
Total Operating Revenues		746	593
Gas Distribution
Operating revenue from contracts with customers		240	182
Other revenues		0	0
Total Operating Revenues		240	182
Residential | Electric Operations
Operating revenue from contracts with customers		371	283
Residential | Gas Distribution
Operating revenue from contracts with customers		151	117
Commercial | Electric Operations
Operating revenue from contracts with customers		228	188
Commercial | Gas Distribution
Operating revenue from contracts with customers		54	41
Industrial | Electric Operations
Operating revenue from contracts with customers		109	87
Industrial | Gas Distribution
Operating revenue from contracts with customers		27	18
Other | Electric Operations
Operating revenue from contracts with customers		32	28
Other | Gas Distribution
Operating revenue from contracts with customers		$ 8	$ 6

[1] See Note 12 for amounts attributable to affiliates.

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Operating Revenue (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Revenue from Contract with Customer [Abstract]
Contract liability balances	$ 5		$ 6
Revenue recognized from contract liability balances	$ 3	$ 3

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Operating Revenue (Balance and Activity Related to Contract Costs Deferred as Regulatory Assets) (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2025	Dec. 31, 2024
Revenues [Abstract]
Beginning balance	$ 10	$ 11
Additional costs	4	0
Amortization	0	(1)
Ending balance	$ 14	$ 10

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Equity (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Class Of Stock [Line Items]
Common stock, par value
Common stock, shares authorized	50,000,000		50,000,000
Common stock, shares issued	40,300,000		40,300,000
Common stock, shares outstanding	40,300,000		40,300,000
Preferred stock, par value
Preferred stock, shares authorized	20,000,000		20,000,000
Preferred stock, shares issued	1,000		1,000
Preferred stock, shares outstanding	1,000		1,000
Contributions from parent	$ 250	$ 0
Dominion Energy
Class Of Stock [Line Items]
Contributions from parent	$ 250

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Long-Term and Short-Term Debt (Narrative) (Detail) - USD ($)		1 Months Ended		3 Months Ended
		Mar. 31, 2025	Jan. 31, 2025	Mar. 31, 2025	Mar. 31, 2024	Apr. 30, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Commercial paper borrowing limit		$ 1,800,000,000		$ 1,800,000,000
Affiliated and related party payables and other		$ 159,000,000		159,000,000			$ 201,000,000
Interest charges	[1]			71,000,000	$ 67,000,000
Maximum [Member]
Debt Instrument [Line Items]
Short term commercial paper maturity period		1 year
Genco
Debt Instrument [Line Items]
Commercial paper borrowing limit		$ 300,000,000		300,000,000
Genco | Maximum [Member]
Debt Instrument [Line Items]
Short term commercial paper maturity period		1 year
DESC | First mortgage bonds
Debt Instrument [Line Items]
Debt instrument, face amount			$ 450,000,000
Interest rate percentage			5.30%
Debt Instrument, Maturity Year			2035
Dominion Energy
Debt Instrument [Line Items]
Affiliated and related party payables and other		$ 558,000,000		558,000,000			942,000,000
Interest charges				11,000,000	$ 10,000,000
Inter company credit facility maximum capacity		900,000,000		900,000,000
Dominion Energy | Genco
Debt Instrument [Line Items]
Inter company credit facility maximum capacity		200,000,000		200,000,000
Dominion Energy | Fuel company
Debt Instrument [Line Items]
Inter company credit facility maximum capacity		400,000,000		400,000,000
Joint Revolving Credit Facility
Debt Instrument [Line Items]
Maximum Facility Sub-Limit	[2]	1,000,000,000		1,000,000,000
Joint Revolving Credit Facility | Commercial Paper
Debt Instrument [Line Items]
Debt instrument, face amount		210,000,000		210,000,000
Joint Revolving Credit Facility | Dominion Energy | Subsequent Event
Debt Instrument [Line Items]
Maximum Facility Sub-Limit						$ 7,000,000,000
Industrial Revenue Bonds
Debt Instrument [Line Items]
Debt instrument, face amount		68,000,000		68,000,000			$ 68,000,000
Intercompany Credit Facility
Debt Instrument [Line Items]
Line of credit, outstanding		227,000,000		227,000,000
Intercompany Credit Facility | Genco
Debt Instrument [Line Items]
Line of credit, outstanding		63,000,000		63,000,000
Letter of Credit
Debt Instrument [Line Items]
Maximum Facility Sub-Limit		$ 3,000,000,000		$ 3,000,000,000

[1] The significant expense categories and amounts in the segment information presented above align with the segment-level information that is regularly provided to DESC’s CODM.

[2] A maximum of $1.0 billion of the facility is available to DESC, assuming adequate capacity is available after giving effect to uses by co-borrowers Dominion Energy and Virginia Power. A sub-limit for DESC is set within the facility limit but can be changed at the option of the co-borrowers multiple times per year. At March 31, 2025, the sub-limit for DESC was $500 million. In April 2025, the sub-limit was increased up to $1.0 billion. If DESC has liquidity needs in excess of its sub-limit, the sub-limit may be changed provided that it does not exceed $1.0 billion or such needs may be satisfied through short-term borrowings from Dominion Energy. This credit facility, as amended in April 2025, matures in April 2030, with the potential to be extended by the borrowers to April 2032. The credit facility can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $3.0 billion (or the sub-limit, whichever is less) of letters of credit.

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Long-Term and Short-Term Debt (Schedule of Line of Credit Facilities) (Detail) - Joint Revolving Credit Facility	Mar. 31, 2025 USD ($)	[1]
Debt Instrument [Line Items]
Maximum Facility Sub-Limit	$ 1,000,000,000
Outstanding Commercial Paper	210,000,000
Outstanding Letters of Credit	$ 0

[1] A maximum of $1.0 billion of the facility is available to DESC, assuming adequate capacity is available after giving effect to uses by co-borrowers Dominion Energy and Virginia Power. A sub-limit for DESC is set within the facility limit but can be changed at the option of the co-borrowers multiple times per year. At March 31, 2025, the sub-limit for DESC was $500 million. In April 2025, the sub-limit was increased up to $1.0 billion. If DESC has liquidity needs in excess of its sub-limit, the sub-limit may be changed provided that it does not exceed $1.0 billion or such needs may be satisfied through short-term borrowings from Dominion Energy. This credit facility, as amended in April 2025, matures in April 2030, with the potential to be extended by the borrowers to April 2032. The credit facility can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $3.0 billion (or the sub-limit, whichever is less) of letters of credit.

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Long-Term and Short-Term Debt (Schedule of Line of Credit Facilities) (Parenthetical) (Detail) - USD ($)		1 Months Ended
		Apr. 30, 2025	Mar. 31, 2025
Minimum [Member] | Subsequent Event
Debt Instrument [Line Items]
Line of credit facility maturity date		2030-04
Maximum [Member] | Subsequent Event
Debt Instrument [Line Items]
Line of credit facility maturity date		2032-04
Joint Revolving Credit Facility
Debt Instrument [Line Items]
Maximum Facility Sub-Limit	[1]		$ 1,000,000,000
Line of Credit Facility
Debt Instrument [Line Items]
Maximum Facility Sub-Limit			500,000,000
Line of Credit Facility | Subsequent Event
Debt Instrument [Line Items]
Maximum Facility Sub-Limit		$ 1,000,000,000
Line of Credit Facility | Maximum [Member] | Subsequent Event
Debt Instrument [Line Items]
Maximum Facility Sub-Limit		$ 1,000,000,000
Letter of Credit
Debt Instrument [Line Items]
Maximum Facility Sub-Limit			$ 3,000,000,000

[1] A maximum of $1.0 billion of the facility is available to DESC, assuming adequate capacity is available after giving effect to uses by co-borrowers Dominion Energy and Virginia Power. A sub-limit for DESC is set within the facility limit but can be changed at the option of the co-borrowers multiple times per year. At March 31, 2025, the sub-limit for DESC was $500 million. In April 2025, the sub-limit was increased up to $1.0 billion. If DESC has liquidity needs in excess of its sub-limit, the sub-limit may be changed provided that it does not exceed $1.0 billion or such needs may be satisfied through short-term borrowings from Dominion Energy. This credit facility, as amended in April 2025, matures in April 2030, with the potential to be extended by the borrowers to April 2032. The credit facility can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $3.0 billion (or the sub-limit, whichever is less) of letters of credit.

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Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Detail)	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Income Tax Disclosure [Abstract]
U.S. statutory rate	21.00%	21.00%
Increases (reductions) resulting from:
State taxes, net of federal benefit	10.80%	3.90%
Reversal of excess deferred income taxes	(2.40%)	(5.30%)
Allowance for equity funds used during construction	0.00%	(0.70%)
Remeasurements and settlements of uncertain tax positions	(17.50%)	0.00%
Other, net	(0.20%)	0.00%
Effective tax rate	11.70%	18.90%

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Income Taxes (Narrative) (Detail) $ in Millions	Mar. 31, 2025 USD ($)
Income Tax Disclosure [Abstract]
Income tax net benefit	$ 18
Unrecognized tax benefit	$ 30

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Derivative Financial Instruments (Narrative) (Detail) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Additional collateral to its counterparties	$ 2	$ 1
Collateral already posted	0	0
Fair value of derivative instruments with credit-related contingent provisions that are in liability position and not fully collateralized with cash	$ 2	$ 1

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Derivative Financial Instruments (Offsetting Assets and Liabilities) (Detail) - USD ($) $ in Millions		Mar. 31, 2025	Dec. 31, 2024
Assets
Derivative [Line Items]
Assets not offset in the consolidated balance sheet	[1]	$ 80	$ 83
Gross amounts not offset in the consolidated balance sheet, financial instruments		0	0
Gross amounts not offset in the consolidated balance sheet, cash collateral received		0	0
Gross amounts not offset in the consolidated balance sheet, net amounts		80	83
Over The Counter [Member] | Assets | Interest Rate Contract [Member]
Derivative [Line Items]
Assets not offset in the consolidated balance sheet	[1]	2	2
Gross amounts not offset in the consolidated balance sheet, financial instruments		0	0
Gross amounts not offset in the consolidated balance sheet, cash collateral received		0	0
Gross amounts not offset in the consolidated balance sheet, net amounts		2	2
Over The Counter [Member] | Assets | Commodity Contract [Member]
Derivative [Line Items]
Assets not offset in the consolidated balance sheet	[1]	78	81
Gross amounts not offset in the consolidated balance sheet, financial instruments		0	0
Gross amounts not offset in the consolidated balance sheet, cash collateral received		0	0
Gross amounts not offset in the consolidated balance sheet, net amounts		78	81
Liability
Derivative [Line Items]
Gross liabilities presented in the consolidated balance sheet		2	1	[2]
Gross amounts not offset in the consolidated balance sheet, financial instruments		0	0
Gross amounts not offset in the consolidated balance sheet, cash collateral paid		0	0
Gross amounts not offset in the consolidated balance sheet, net amounts		2	1
Liability | Over The Counter [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Gross liabilities presented in the consolidated balance sheet		2	1	[2]
Gross amounts not offset in the consolidated balance sheet, financial instruments		0	0
Gross amounts not offset in the consolidated balance sheet, cash collateral paid		0	0
Gross amounts not offset in the consolidated balance sheet, net amounts		$ 2	$ 1

[1] Excludes derivative assets of $199 million and $289 million at March 31, 2025 and December 31, 2024, respectively, which are not subject to master netting or similar arrangements.

[2] Excludes derivative liabilities of $5 million at March 31, 2025, which are not subject to master netting or similar arrangements. DESC did not have any derivative liabilities at December 31, 2024 which were not subject to master netting or similar arrangements.

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Derivative Financial Instruments (Offsetting Assets and Liabilities) (Parenthetical) (Details) - USD ($)	Mar. 31, 2025	Dec. 31, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative assets not subject to master netting or similar arrangements	$ 199,000,000	$ 289,000,000
Derivative liability not subject to master netting or similar arrangements	$ 5,000,000	$ 0

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Derivative Financial Instruments (Schedule of Volume of Derivative Activity) (Detail) MWh in Millions, Bcf in Millions	3 Months Ended
	Mar. 31, 2025 USD ($) Bcf MWh
Interest Rate Swap Current [Member]
Derivative [Line Items]
Interest rate | $	$ 0	[1]
Interest Rate Swap Current [Member] | Natural Gas (bcf) [Member]
Derivative [Line Items]
Basis | Bcf	41	[2]
Interest Rate Swap Current [Member] | Electricity [Member]
Derivative [Line Items]
Fixed price | MWh	2
Interest Rate Swap Noncurrent [Member]
Derivative [Line Items]
Interest rate | $	$ 71,000,000	[1]
Interest Rate Swap Noncurrent [Member] | Natural Gas (bcf) [Member]
Derivative [Line Items]
Basis | Bcf	31	[2]
Interest Rate Swap Noncurrent [Member] | Electricity [Member]
Derivative [Line Items]
Fixed price | MWh	22

[1] Maturity is determined based on final settlement period.

[2] Includes options.

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Derivative Financial Instruments (Fair Value of Derivatives) (Detail) - USD ($) $ in Millions		Mar. 31, 2025	Dec. 31, 2024
Derivative [Line Items]
Derivative Asset, Current	[1]	$ 73	$ 63
Derivative Asset, Noncurrent	[1]	206	309
Derivative Liability, Current		1	0
Derivative Liability, Noncurrent		6	1
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset, Current		$ 73	$ 63
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]		Other Assets, Current	Other Assets, Current
Derivative Asset, Noncurrent		$ 206	$ 309
Derivative Asset, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Regulated Entity, Other Assets, Noncurrent	Regulated Entity, Other Assets, Noncurrent
Derivative Assets		$ 279	$ 372
Derivative Asset, Statement of Financial Position [Extensible Enumeration]		Assets	Assets
Derivative Liability, Current		$ 1	$ 0
Derivative Liability, Current, Statement of Financial Position [Extensible Enumeration]		Liabilities, Current	Liabilities, Current
Derivative Liability, Noncurrent		$ 6	$ 1
Derivative Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Liabilities, Noncurrent	Liabilities, Noncurrent
Derivative Liability		$ 7	$ 1
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		Liabilities and Equity	Liabilities and Equity
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivative [Line Items]
Derivative Asset, Current		$ 73	$ 63
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]		Other Assets, Current	Other Assets, Current
Derivative Asset, Noncurrent		$ 204	$ 307
Derivative Asset, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Regulated Entity, Other Assets, Noncurrent	Regulated Entity, Other Assets, Noncurrent
Derivative Liability, Current		$ 0	$ 0
Derivative Liability, Current, Statement of Financial Position [Extensible Enumeration]		Liabilities, Current	Liabilities, Current
Derivative Liability, Noncurrent		$ 5	$ 0
Derivative Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Liabilities, Noncurrent	Liabilities, Noncurrent
Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Asset, Current		$ 0
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]		Other Assets, Current
Derivative Asset, Noncurrent		$ 2	$ 2
Derivative Asset, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Regulated Entity, Other Assets, Noncurrent	Regulated Entity, Other Assets, Noncurrent
Derivative Liability, Current		$ 1
Derivative Liability, Current, Statement of Financial Position [Extensible Enumeration]		Liabilities, Current
Derivative Liability, Noncurrent		$ 1	$ 1
Derivative Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Liabilities, Noncurrent	Liabilities, Noncurrent

[1] See Note 12 for amounts attributable to affiliates.

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Derivative Financial Instruments (Derivatives in Cash Flow Hedging Relationships) (Detail) - Cash Flow Hedging [Member] - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2025	Mar. 31, 2024
Derivative [Line Items]
Increase (Decrease) in Derivatives Subject to Regulatory Treatment	[1],[2]	$ 0	$ 0
Interest Rate Contract [Member]
Derivative [Line Items]
Increase (Decrease) in Derivatives Subject to Regulatory Treatment	[1],[2]	$ 0	$ 0

[1] All derivatives in cash flow hedging relationships have settled and are being amortized over the life of the debt.

[2] Represents net derivative activity deferred into and amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/ liabilities have no associated effect in the Consolidated Statements of Comprehensive Income.

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Derivative Financial Instruments (Derivatives Not Designated as Hedging Instruments) (Detail) - Not Designated as Hedging Instruments [Member] - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2025	Mar. 31, 2024
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	[1]	$ 2	$ (3)
Commodity Contract [Member] | Purchased Power [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	[1]	3	(2)
Interest Rate Contract [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	[1]	$ (1)	$ (1)
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]		Interest Expense, Operating and Nonoperating	Interest Expense, Operating and Nonoperating

[1] Includes derivative activity amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/liabilities have no associated effect in the Consolidated Statements of Comprehensive Income.

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Fair Value Measurements, Including Derivatives (Schedule of Quantitative Information About Level 3 Fair Value Measurements) (Details) - USD ($)		Mar. 31, 2025	Dec. 31, 2024	[5]
Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets, fair value		$ 275,000,000
Total liability, fair value		5,000,000
Electricity [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets, fair value		199,000,000
Total liability, fair value		5,000,000
Natural gas [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets, fair value	[1]	76,000,000
Assets [Member] | Electricity [Member] | Fair Value, Inputs, Level 3 [Member] | Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value inputs market price (per MWh)	[2]	30
Assets [Member] | Electricity [Member] | Fair Value, Inputs, Level 3 [Member] | Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value inputs market price (per MWh)	[2]	83
Assets [Member] | Electricity [Member] | Fair Value, Inputs, Level 3 [Member] | Weighted average [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value inputs market price (per MWh)	[3]	48
Assets [Member] | Natural gas [Member] | Fair Value, Inputs, Level 3 [Member] | Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value inputs market price per decatherm	[2]	$ 3
Fair value inputs price volatility	[4]	11.00%
Assets [Member] | Natural gas [Member] | Fair Value, Inputs, Level 3 [Member] | Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value inputs market price per decatherm	[2]	$ 8
Fair value inputs price volatility	[4]	74.00%
Assets [Member] | Natural gas [Member] | Fair Value, Inputs, Level 3 [Member] | Weighted average [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value inputs market price per decatherm	[3]	$ 4
Fair value inputs price volatility	[3]	44.00%
Liability [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liability, fair value		$ 2,000,000	$ 1,000,000
Liability [Member] | Electricity [Member] | Fair Value, Inputs, Level 3 [Member] | Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value inputs market price (per MWh)	[2]	30
Liability [Member] | Electricity [Member] | Fair Value, Inputs, Level 3 [Member] | Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value inputs market price (per MWh)	[2]	81
Liability [Member] | Electricity [Member] | Fair Value, Inputs, Level 3 [Member] | Weighted average [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value inputs market price (per MWh)	[3]	$ 50

[1] Includes basis.

[2] Represents market prices beyond defined terms for Levels 1 and 2.

[3] Averages weighted by volume.

[4] Represents volatilities unrepresented in published markets.

[5] Excludes derivative liabilities of $5 million at March 31, 2025, which are not subject to master netting or similar arrangements. DESC did not have any derivative liabilities at December 31, 2024 which were not subject to master netting or similar arrangements.

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Fair Value Measurements, Including Derivatives (Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis) (Details) - Fair value, recurring - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Assets
Total assets	$ 308	$ 401
Liabilities
Total liabilities	7	1
Commodity Contract [Member]
Assets
Derivatives	277	370
Liabilities
Total liabilities	5
Interest Rate Contract [Member]
Assets
Derivatives	2	2
Liabilities
Derivatives	2	1
Cash Equivalents and Other [Member]
Assets
Investments	29	29
Level 1
Assets
Total assets	29	29
Liabilities
Total liabilities	0	0
Level 1 | Commodity Contract [Member]
Assets
Derivatives	0	0
Liabilities
Total liabilities	0
Level 1 | Interest Rate Contract [Member]
Assets
Derivatives	0	0
Liabilities
Derivatives	0	0
Level 1 | Cash Equivalents and Other [Member]
Assets
Investments	29	29
Level 2
Assets
Total assets	4	2
Liabilities
Total liabilities	2	1
Level 2 | Commodity Contract [Member]
Assets
Derivatives	2	0
Liabilities
Total liabilities	0
Level 2 | Interest Rate Contract [Member]
Assets
Derivatives	2	2
Liabilities
Derivatives	2	1
Level 2 | Cash Equivalents and Other [Member]
Assets
Investments	0	0
Level 3
Assets
Total assets	275	370
Liabilities
Total liabilities	5	0
Level 3 | Commodity Contract [Member]
Assets
Derivatives	275	370
Liabilities
Total liabilities	5
Level 3 | Interest Rate Contract [Member]
Assets
Derivatives	0	0
Liabilities
Derivatives	0	0
Level 3 | Cash Equivalents and Other [Member]
Assets
Investments	$ 0	$ 0

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Fair Value Measurements, Including Derivatives (Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis and Included in Level 3) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Regulatory Assets
Beginning balance	$ 370	$ 176
Included in earnings:
Purchased power	3	(2)
Settlements	(14)	2
Purchases	0	7
Ending balance	270	253
Other Regulatory Assets Liabilities
Included in earnings:
Included in regulatory assets/liabilities	$ (89)	$ 70

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Fair Value Measurements, Including Derivatives (Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis) (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Unrealized gains and losses	$ 0	$ 0

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Fair Value Measurements, Including Derivatives (Schedule of Carrying Values and Estimated Fair Values of Debt Instruments) (Detail) - USD ($) $ in Millions		Mar. 31, 2025	Dec. 31, 2024
Carrying Amount
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term debt	[1]	$ 4,666	$ 4,220
Affiliated long-term debt		230	230
Estimated Fair Value
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term debt	[1],[2]	4,632	4,142
Affiliated long-term debt	[2]	$ 230	$ 230

[1] Carrying amount includes current portions, if any, included in securities due within one year and amounts which represent the unamortized debt issuance costs and discount or premium.

[2] Fair value is estimated using market prices, where available, and interest rates currently available for issuance of debt with similar terms and remaining maturities. All fair value measurements are classified as Level 2. The carrying amount of debt issuances with short-term maturities and variable rates refinanced at current market rates is a reasonable estimate of their fair value.

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Employee Benefit Plans (Components of Net Periodic Benefit Cost (Credit) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2	$ 2
Interest cost	9	8
Expected return on assets	(10)	(9)
Amortization of actuarial losses	1	2
Net periodic benefit cost (credit)	2	3
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
Interest cost	2	2
Expected return on assets	0	0
Amortization of actuarial losses	(1)	(1)
Net periodic benefit cost (credit)	$ 1	$ 1

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Employee Benefit Plans (Narrative) (Detail) - Pension Plan - USD ($)	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, contributions by employer		$ 0
Defined benefit plan, expected contributions in 2025		$ 3,000,000
Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, contributions by employer	$ 1,000,000

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Commitments and Contingencies (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Loss Contingencies [Line Items]
Personal injury or wrongful death charges		$ 6
Insurance receivable	$ 19		$ 10
Reserves related to personal injury or wrongful death cases	16		$ 7
Maximum [Member]
Loss Contingencies [Line Items]
Personal injury or wrongful death charges	$ 1

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Commitments and Contingencies (Environmental Matters) (Narrative) (Detail) gal in Millions, $ in Millions		1 Months Ended						3 Months Ended
	Oct. 31, 2014 MGD Facility	May 31, 2024 Station	Oct. 31, 2020	Nov. 30, 2019 gal	Sep. 30, 2017 Petition	Apr. 30, 2017 Petition	Aug. 31, 2016 T	Mar. 31, 2025 USD ($) Indicator Facility Product	Mar. 31, 2024 USD ($)
Loss Contingencies [Line Items]
Measurement of groundwater withdrawals | gal				3
Number of manufacturing gas plant decommissioned sites that contain residues of byproduct chemicals | Product								4
Environmental remediation costs recognized in regulatory assets | $								$ 33
Number of facilities inactive subject to final rule | Facility								3
Increase in regulatory assets | $								$ 98	$ (79)
Unfavorable Regulatory Action | CWA
Loss Contingencies [Line Items]
Electric generating stations with water withdrawals with heightened entrainment analysis under CWA | MGD	2
Number of mandatory facility specific factors. | Indicator								5
Number of optional facility specific factors | Indicator								6
Unfavorable Regulatory Action | CWA | DESC
Loss Contingencies [Line Items]
Number of DESC facilities subject to final regulations | Facility	5
Maximum [Member]
Loss Contingencies [Line Items]
Estimated environmental remediation activities at manufacturing gas plant sites | $								$ 1
Environmental Protection Agency And State Regulatory Agencies [Member] | Hydroelectric Facilities
Loss Contingencies [Line Items]
Number of DESC hydroelectric facilities subject to regulations | Facility	5
EPA
Loss Contingencies [Line Items]
Number of petition agreed for reconsideration | Petition					2
EPA | Unfavorable Regulatory Action
Loss Contingencies [Line Items]
Electric generating stations with water withdrawals under CWA | MGD	125
EPA | Unfavorable Regulatory Action | CWA | Final Rule to Revise Effluent Limitations Guidelines for Steam Electric Power Generating Category
Loss Contingencies [Line Items]
Number of separate petitions for reconsideration granted | Petition						2
Loss contingencies facility retirement period		2034
EPA | Minimum [Member] | Unfavorable Regulatory Action | CWA | Final Rule to Revise Effluent Limitations Guidelines for Steam Electric Power Generating Category
Loss Contingencies [Line Items]
Loss contingencies individual facilities circumstances period			2021
EPA | Maximum [Member]
Loss Contingencies [Line Items]
Number of stations inactive subject to final rule | Station		7
EPA | Maximum [Member] | Unfavorable Regulatory Action | CWA | Final Rule to Revise Effluent Limitations Guidelines for Steam Electric Power Generating Category
Loss Contingencies [Line Items]
Loss contingencies individual facilities circumstances period		2029	2028
Carbon Regulations
Loss Contingencies [Line Items]
Significant emission rate per year CO2 equivalent | T							75,000

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Commitments and Contingencies (Surety Bonds) (Narrative) (Details)	Mar. 31, 2025 USD ($)
Surety Bonds
Loss Contingencies [Line Items]
Guarantee obligation	$ 24,000,000

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Operating Segments - Schedule of Segment Reporting Information, by Segment (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Segment Reporting Information [Line Items]
Operating Revenue	[1]	$ 986	$ 775
Fuel used in electric generation	[2]	204	145
Purchased power	[1],[2]	22	10
Gas purchased for resale	[2]	126	79
Other operations and maintenance	[2]	174	163
Depreciation and amortization	[2]	140	136
Other taxes	[1],[2]	82	78
Total operating expenses		748	611
Other income (expense), net	[3]	3	1
Interest charges, net of AFUDC	[2]	71	67
Income tax expense	[2]	20	18
Comprehensive Income Attributable to Noncontrolling Interest	[3]	8	6
Comprehensive Income (Loss) Available (Attributable) to Common Shareholder		142	74
Capital expenditures		297	268
Total assets		17,118		$ 17,041
Dominion Energy South Carolina, Inc. [Member]
Segment Reporting Information [Line Items]
Operating Revenue		986	775
Fuel used in electric generation	[2]	204	145
Purchased power	[2]	22	10
Gas purchased for resale	[2]	126	79
Other operations and maintenance	[2]	174	163
Depreciation and amortization	[2]	140	136
Other taxes	[2]	82	78
Total operating expenses		748	611
Other income (expense), net	[3]	3	1
Interest charges, net of AFUDC	[2]	71	67
Income tax expense	[2]	18	17
Comprehensive Income Attributable to Noncontrolling Interest	[3]	8	6
Comprehensive Income (Loss) Available (Attributable) to Common Shareholder		144	75
Capital expenditures		297	268
Total assets		17,100
Corporate and Other
Segment Reporting Information [Line Items]
Operating Revenue		0	0
Fuel used in electric generation	[2]	0	0
Purchased power	[2]	0	0
Gas purchased for resale	[2]	0	0
Other operations and maintenance	[2]	0	0
Depreciation and amortization	[2]	0	0
Other taxes	[2]	0	0
Total operating expenses		0	0
Other income (expense), net	[3]	0	0
Interest charges, net of AFUDC	[2]	0	0
Income tax expense	[2]	2	1
Comprehensive Income Attributable to Noncontrolling Interest	[3]	0	0
Comprehensive Income (Loss) Available (Attributable) to Common Shareholder		(2)	(1)
Capital expenditures		0	$ 0
Total assets		$ 0

[1] See Note 12 for amounts attributable to affiliates.

[2] The significant expense categories and amounts in the segment information presented above align with the segment-level information that is regularly provided to DESC’s CODM.

[3] Items designated are other segment items for each reportable segment.

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Affiliated and Related Party Transactions (Schedule of Affiliated Transactions - Income Statement) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2025	Mar. 31, 2024
Related Party Transaction [Line Items]
Operating Revenues - Electric from sales to affiliate		$ 1	$ 1
Operating Expenses - Other taxes from affiliate		3	3
Related Party | DES
Related Party Transaction [Line Items]
Direct and allocated costs	[1]	62	53
Solar Affiliates [Member]
Related Party Transaction [Line Items]
Purchases from affiliate		$ 3	$ 1

[1] Includes capitalized expenditures of $19 million and $12 million for the three months ended March 31, 2025 and 2024, respectively.

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Affiliated and Related Party Transactions (Schedule of Affiliated Transactions - Income Statement) (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
DES
Related Party Transaction [Line Items]
Capitalized expenditures	$ 19	$ 12

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Affiliated and Related Party Transactions (Schedule of Affiliated Transactions - Balance Sheet) (Detail) - USD ($) $ in Millions		Mar. 31, 2025	Dec. 31, 2024
Related Party Transaction [Line Items]
Affiliated and related party payables and other		$ 159	$ 201
Derivative assets with affiliates	[1]	33	48
DES | Related Party
Related Party Transaction [Line Items]
Affiliated and related party payables and other		19	19
SCANA Corporation | Related Party
Related Party Transaction [Line Items]
Affiliated and related party payables and other		$ 7	$ 7

[1] Includes amounts recorded in current derivative assets of $6 million and $4 million as of March 31, 2025 and December 31, 2024, respectively, and amounts recorded in noncurrent derivative assets of $27 million and $44 million as of March 31, 2025 and December 31, 2024, respectively.

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Affiliated and Related Party Transactions (Schedule of Affiliated Transactions - Balance Sheet) (Parenthetical) (Detail) - USD ($) $ in Millions		Mar. 31, 2025	Dec. 31, 2024
Related Party Transaction [Line Items]
Derivative assets with affiliates	[1]	$ 33	$ 48
Current Derivative Assets [Member]
Related Party Transaction [Line Items]
Derivative assets with affiliates		6	4
Noncurrent Derivative Assets [Member]
Related Party Transaction [Line Items]
Derivative assets with affiliates		$ 27	$ 44

[1] Includes amounts recorded in current derivative assets of $6 million and $4 million as of March 31, 2025 and December 31, 2024, respectively, and amounts recorded in noncurrent derivative assets of $27 million and $44 million as of March 31, 2025 and December 31, 2024, respectively.

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Other Income (Expense), Net (Components of Other Income (Expense), Net) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2025	Mar. 31, 2024
Income Statement [Abstract]
Other income		$ 5	$ 2
Gains on sales of assets		0	1
Other expense		(2)	(5)
Allowance for equity funds used during construction		0	3
Other income (expense), net	[1]	$ 3	$ 1

[1] Items designated are other segment items for each reportable segment.