Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2024

Accounting Policies [Abstract]

Summary of Ratio of Depreciation to Average Depreciable Property and Average Service Lives for Utility Plan in Service

For utility operations, the ratio of depreciation provisions to average depreciable property was as follows for the years ended December 31:

	2024			2023			2022
Avista Utilities		3.45	%		3.52	%		3.50	%
Alaska Electric Light and Power Company		2.80	%		2.78	%		2.78	%

The average service lives for the following broad categories of utility plant in service are (in years):

	Avista Utilities		Alaska Electric Light and Power Company
Electric thermal/other production		27		41
Hydroelectric production		81		42
Electric transmission		44		43
Electric distribution		42		39
Natural gas distribution property		44	N/A
Other shorter-lived general plant		8		18

The gross balances of the major classifications of property, plant and equipment are detailed in the following table as of December 31 (dollars in millions):

	2024		2023
Avista Utilities:
Electric production	$	1,523	$	1,498
Electric transmission		1,105		1,059
Electric distribution		2,580		2,383
Electric construction work-in-progress (CWIP) and other		452		395
Electric total		5,660		5,335
Natural gas underground storage		63		60
Natural gas distribution		1,624		1,539
Natural gas CWIP and other		95		92
Natural gas total		1,782		1,691
Common plant (including CWIP)		760		760
Total Avista Utilities		8,202		7,786
AEL&P:
Electric production		120		119
Electric transmission		23		23
Electric distribution		36		32
Electric CWIP and other		26		9
Electric total		205		183
Common plant		11		10
Total AEL&P		216		193
Total gross utility property		8,418		7,979
Other (1)		6		6
Total	$	8,424	$	7,985

(1)Included in other property and investments-net and other non-current assets on the Consolidated Balance Sheets.

Summary of Effective AFUDC Rate

The effective AFUDC rate was the following for the years ended December 31:

	2024			2023			2022
Avista Utilities		7.03	%		7.03	%		7.12	%
Alaska Electric Light and Power Company		8.47	%		8.61	%		8.08	%

Stock-Based Compensation

The Company recorded stock-based compensation expense (included in other operating expenses) and income tax benefits in the Consolidated Statements of Income of the following amounts for the years ended December 31 (dollars in millions):

	2024		2023		2022
Stock-based compensation expense	$	8	$	7	$	8
Income tax benefits		2		2		2

The following table summarizes the number of grants, vested and unvested shares, earned shares (based on market metrics), and other pertinent information related to the Company's stock compensation awards for the years ended December 31:

	2024		2023		2022
Restricted Shares
Shares granted during the year		82,433		76,806		115,746
Shares vested during the year		75,107		75,007		44,829
Unvested shares at end of year		158,464		152,140		157,860
Unrecognized compensation expense at end of year    (in millions)	$	3	$	3	$	4
TSR Awards
TSR shares granted during the year		45,739		34,912		69,814
TSR shares vested during the year		64,640		61,456		43,730
TSR shares earned based on market metrics		35,552		44,863		48,890
Unvested TSR shares at end of year		77,530		96,915		130,567
Unrecognized compensation expense at end of year    (in millions)	$	2	$	2	$	4
CEPS Awards
CEPS shares granted during the year		137,161		104,685		69,814
CEPS shares vested during the year		64,640		61,456		43,730
CEPS shares earned based on performance metrics		29,088		33,801		—
Unvested CEPS shares at end of year		232,486		161,235		130,567
Unrecognized compensation expense at end of year    (in millions)	$	3	$	2	$	2

Other Expense (Income) - Net

Other income - net consisted of the following items for the years ended December 31 (dollars in millions):

	2024			2023			2022
Interest income	$	5		$	6		$	2
Interest on regulatory deferrals		9			9			2
Equity-related AFUDC		9			7			7
Non-service portion of pension and other postretirement benefit    expenses		2			—			3
Earnings (losses) on investments		(7	)		(3	)		48
Other income		4			—			1
Total	$	22		$	19		$	63

Allowance for Doubtful Accounts

The following table presents the activity in the allowance for doubtful accounts during the years ended December 31 (dollars in millions):

	2024			2023			2022
Allowance as of the beginning of the year	$	5		$	6		$	10
Additions expensed during the year		7			7			—
Net deductions		(7	)		(8	)		(4	)
Allowance as of the end of the year	$	5		$	5		$	6

The Company has received grants from various government agencies to assist customers with their energy bills. The Company received these grant funds and applied them to customer accounts, reducing accounts receivable balances. These grants totaled $10 million in 2024, $2 million in 2023 and $6 million in 2022.

Estimated Retirement Costs Collected from Customers

The Company records the amount of estimated retirement costs collected from customers (that do not represent legal or contractual obligations) and includes them as a non-current regulatory liability on the Consolidated Balance Sheets in the following amounts as of December 31 (dollars in millions):

	2024		2023
Regulatory liability for utility plant retirement costs	$	448	$	417

Summary of Appropriated Retained Earnings Amount Included in Retained Earnings

The appropriated retained earnings amounts included in retained earnings were as follows as of December 31 (dollars in millions):

	2024		2023
Appropriated retained earnings	$	62	$	59