Segment Information

12 Months Ended

Dec. 31, 2024

Segment Reporting [Abstract]

Segment Reporting Disclosure [Text Block]

Segment Information - MGE Energy and MGE.

The electric utility business purchases, generates and distributes electricity, and contracts for transmission service. The gas utility business purchases and distributes natural gas and contracts for the transportation of natural gas. Both the electric and gas segments operate through MGE Energy's principal subsidiary, MGE.

The nonregulated energy operations are conducted through MGE Energy's subsidiaries: MGE Power, MGE Power Elm Road, and MGE Power West Campus. These subsidiaries own electric generating capacity that they lease to MGE to assist MGE. MGE Power Elm Road has an ownership interest in two coal-fired generating units in Oak Creek, Wisconsin, which are leased to MGE, and MGE Power West Campus owns a controlling interest in the electric generation plant of a natural gas-fired cogeneration facility on the UW campus. MGE Power West Campus's portion is also leased to MGE.

The transmission investment segment invests in ATC, a company that provides electric transmission services primarily in Wisconsin, and ATC Holdco, a company formed to pursue electric transmission development and investments outside of Wisconsin. These investments are held in MGE Transco and MGEE Transco, respectively. See Footnote 7 for further discussion.

The "All Other" segment includes: corporate, CWDC, MAGAEL, MGE State Energy Services, MGE Services, and North Mendota. These entities' operations consist of investing in companies and property which relate to the regulated operations, and financing the regulated operations.

General corporate expenses include the cost of executive management, corporate accounting and finance, information technology, risk management, human resources and legal functions, and employee benefits that are allocated to electric and gas segments based on formulas prescribed by the PSCW. Identifiable assets are those used in MGE's operations in each segment.

Sales between our electric and gas segments are based on PSCW approved tariffed rates. Additionally, intersegment operations related to the leasing arrangement between our electric segment and MGE Power Elm Road/MGE Power West Campus are based on terms previously approved by the PSCW. Consistent with internal reporting, management has presented the direct financing capital leases between MGE and MGE Power Elm Road/MGE Power West Campus based on actual lease payments included in rates. Lease payments made by MGE to MGE Power Elm Road and MGE Power West Campus are shown as operating expenses. The lease payments received by MGE Power Elm Road and MGE Power West

Campus from MGE are shown as lease income in interdepartmental revenues. The depreciation expense associated with the Elm Road Units and WCCF is reflected in the nonregulated energy segment.

The Chief Executive Officer, Chief Operating Decision Maker (CODM), utilizes various reported measures of segment profit or loss to assess performance and allocate resources within the organization. Key metrics such as segment revenue, expenses, capital expenditures, and net income provide the CODM with valuable insights into each segment's financial health and operational efficiency. For instance, segment revenue helps gauge market performance and sales effectiveness, while net income reveals the profitability of core operations by accounting for both direct and indirect costs. By analyzing these measures, the CODM can identify high-performing segments that warrant increased investment, reallocate resources from underperforming areas, and implement strategic changes to optimize overall performance. This targeted approach ensures that resources are directed toward segments with the greatest potential for growth and profitability, aligning with the organization's broader strategic objectives.

Fuel and Purchase Power and Purchase Gas Costs are significant segment expenses as defined in Segment Reporting. The CODM does not review disaggregated assets on a segment basis; therefore, such information is not presented.

The following table shows segment information for MGE Energy's and MGE's operations:

(In thousands) MGE Energy	Electric			Gas			Non-Regulated Energy			Transmission Investment			Total Reportable Segments			All Others			Consolidation/ Elimination Entries			Consolidated Total
Year Ended December 31, 2024
Operating revenues	$	497,673		$	178,587		$	684		$	—		$	676,944		$	—		$	—		$	676,944
Interdepartmental revenues		(194	)		14,983			43,831			—			58,620			—			(58,620	)		—
Total operating revenues		497,479			193,570			44,515			—			735,564			—			(58,620	)		676,944
Fuel and purchased power		(90,726	)		—			—			—			(90,726	)		—			3,880			(86,846	)
Purchased gas costs		—			(93,834	)		—			—			(93,834	)		—			11,141			(82,693	)
Depreciation and amortization		(84,264	)		(16,779	)		(7,538	)		—			(108,581	)		—			—			(108,581	)
Interest expense		(25,616	)		(6,943	)		(3,793	)		—			(36,352	)		—			—			(36,352	)
Other segment items(a)		(225,985	)		(60,290	)		(113	)		—			(286,388	)		(793	)		43,599			(243,582	)
Income tax (provision) benefit		3,620			(1,995	)		(9,009	)		(3,345	)		(10,729	)		133			—			(10,596	)
Equity in earnings of investments		—			—			—			12,275			12,275			—			—			12,275
Net income (loss)		74,508			13,729			24,062			8,930			121,229			(660	)		—			120,569
Year Ended December 31, 2023
Operating revenues	$	489,729		$	200,012		$	690		$	—		$	690,431		$	—		$	—		$	690,431
Interdepartmental revenues		922			15,501			41,586			—			58,009			—			(58,009	)		—
Total operating revenues		490,651			215,513			42,276			—			748,440			—			(58,009	)		690,431
Fuel and purchased power		(102,520	)		—			—			—			(102,520	)		—			3,669			(98,851	)
Purchased gas costs		—			(118,509	)		—			—			(118,509	)		—			11,862			(106,647	)
Depreciation and amortization		(77,440	)		(15,531	)		(7,381	)		—			(100,352	)		—			—			(100,352	)
Interest expense		(22,883	)		(6,146	)		(4,062	)		—			(33,091	)		—			—			(33,091	)
Other segment items(a)		(201,680	)		(54,084	)		(107	)		2			(255,869	)		(3,228	)		42,478			(216,619	)
Income tax (provision) benefit		(10,182	)		(7,175	)		(8,370	)		(2,897	)		(28,624	)		821			—			(27,803	)
Equity in earnings of investments		—			—			—			10,631			10,631			—			—			10,631
Net income (loss)		75,946			14,068			22,356			7,736			120,106			(2,407	)		—			117,699
Year Ended December 31, 2022
Operating revenues	$	465,167		$	248,672		$	680		$	—		$	714,519		$	—		$	—		$	714,519
Interdepartmental revenues		(44	)		34,073			41,556			—			75,585			—			(75,585	)		—
Total operating revenues		465,123			282,745			42,236			—			790,104			—			(75,585	)		714,519
Fuel and purchased power		(111,915	)		—			—			—			(111,915	)		—			3,765			(108,150	)
Purchased gas costs		—			(182,904	)		—			—			(182,904	)		—			30,334			(152,570	)
Depreciation and amortization		(62,896	)		(15,262	)		(7,391	)		—			(85,549	)		—			—			(85,549	)
Interest expense		(18,884	)		(4,867	)		(4,322	)		—			(28,073	)		—			—			(28,073	)
Other segment items(a)		(198,942	)		(53,005	)		(161	)		—			(252,108	)		(1,515	)		41,486			(212,137	)
Income tax (provision) benefit		(7,299	)		(8,492	)		(8,272	)		(2,489	)		(26,552	)		328			—			(26,224	)
Equity in earnings of investments		—			—			—			9,136			9,136			—			—			9,136
Net income (loss)		65,187			18,215			22,090			6,647			112,139			(1,187	)		—			110,952

(a)Other segment items include AFUDC Income, Other Income, Net, Other Operations and Maintenance, Other General Taxes, and Interest Revenue.

(In thousands) MGE	Electric			Gas			Non-Regulated Energy			Total Reportable Segments			Consolidation/ Elimination Entries			Consolidated Total
Year Ended December 31, 2024
Operating revenues	$	497,673		$	178,587		$	684		$	676,944		$	—		$	676,944
Interdepartmental revenues		(194	)		14,983			43,831			58,620			(58,620	)		—
Total operating revenues		497,479			193,570			44,515			735,564			(58,620	)		676,944
Fuel and purchased power		(90,726	)		—			—			(90,726	)		3,880			(86,846	)
Purchased gas costs		—			(93,834	)		—			(93,834	)		11,141			(82,693	)
Depreciation and amortization		(84,264	)		(16,779	)		(7,538	)		(108,581	)		—			(108,581	)
Interest expense		(25,616	)		(6,943	)		(3,793	)		(36,352	)		—			(36,352	)
Other segment items(a)		(225,985	)		(60,290	)		(113	)		(286,388	)		43,599			(242,789	)
Income tax benefit (provision)		3,620			(1,995	)		(9,009	)		(7,384	)		—			(7,384	)
Net income attributable to noncontrolling interest, net of tax		—			—			—			—			(22,855	)		(22,855	)
Net income attributable to MGE		74,508			13,729			24,062			112,299			(22,855	)		89,444
Year Ended December 31, 2023
Operating revenues	$	489,729		$	200,012		$	690		$	690,431		$	—		$	690,431
Interdepartmental revenues		922			15,501			41,586			58,009			(58,009	)		—
Total operating revenues		490,651			215,513			42,276			748,440			(58,009	)		690,431
Fuel and purchased power		(102,520	)		—			—			(102,520	)		3,669			(98,851	)
Purchased gas costs		—			(118,509	)		—			(118,509	)		11,862			(106,647	)
Depreciation and amortization		(77,440	)		(15,531	)		(7,381	)		(100,352	)		—			(100,352	)
Interest expense		(22,883	)		(6,146	)		(4,062	)		(33,091	)		—			(33,091	)
Other segment items(a)		(201,680	)		(54,084	)		(107	)		(255,871	)		42,478			(213,393	)
Income tax provision		(10,182	)		(7,175	)		(8,370	)		(25,727	)		—			(25,727	)
Net income attributable to noncontrolling interest, net of tax		—			—			—			—			(21,868	)		(21,868	)
Net income attributable to MGE		75,946			14,068			22,356			112,370			(21,868	)		90,502
Year Ended December 31, 2022
Operating revenues	$	465,167		$	248,672		$	680			714,519		$	—			714,519
Interdepartmental revenues		(44	)		34,073			41,556			75,585			(75,585	)		—
Total operating revenues		465,123			282,745			42,236			790,104			(75,585	)		714,519
Fuel and purchased power		(111,915	)		—			—			(111,915	)		3,765			(108,150	)
Purchased gas costs		—			(182,904	)		—			(182,904	)		30,334			(152,570	)
Depreciation and amortization		(62,896	)		(15,262	)		(7,391	)		(85,549	)		—			(85,549	)
Interest expense		(18,884	)		(4,867	)		(4,322	)		(28,073	)		—			(28,073	)
Other segment items(a)		(198,942	)		(53,005	)		(161	)		(252,108	)		41,486			(210,622	)
Income tax provision		(7,299	)		(8,492	)		(8,272	)		(24,063	)		—			(24,063	)
Net income attributable to noncontrolling interest, net of tax		—			—			—			—			(21,576	)		(21,576	)
Net income attributable to MGE		65,187			18,215			22,090			105,492			(21,576	)		83,916

(a)Other segment items include AFUDC Income, Other Income, Net, Other Operations and Maintenance, Other General Taxes, and Interest Revenue.

The following table shows segment information for MGE Energy's and MGE's capital expenditures:

	Utility				Consolidated
(In thousands) MGE Energy	Electric		Gas		Non-regulated Energy		Transmission Investment		All Others		Consolidation/ Elimination Entries		Total
Year ended Dec. 31, 2024	$	192,469	$	38,101	$	6,355	$	—	$	—	$	—	$	236,925
Year ended Dec. 31, 2023		180,743		36,402		4,926		—		—		—		222,071
Year ended Dec. 31, 2022		141,273		27,656		6,101		—		—		—		175,030

	Utility				Consolidated
(In thousands) MGE	Electric		Gas		Non-regulated Energy		Consolidation/ Elimination Entries		Total
Year ended Dec. 31, 2024	$	192,469	$	38,101	$	6,355	$	—	$	236,925
Year ended Dec. 31, 2023		180,743		36,402		4,926		—		222,071
Year ended Dec. 31, 2022		141,273		27,656		6,101		—		175,030