Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Recurring Fair Value Measurements

Carrying amounts and the related estimated fair values of other financial instruments at December 31 were as follows (in millions):

Alliant Energy	2023					2022
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Money market fund investments	$45	$45	$—	$—	$45	$10	$10	$—	$—	$10
Commodity derivatives	88	—	59	29	88	237	—	206	31	237
Interest rate derivatives	1	—	1	—	1	—	—	—	—	—
Deferred proceeds	216	—	—	216	216	185	—	—	185	185
Liabilities and equity:
Commodity derivatives	98	—	93	5	98	79	—	67	12	79
Long-term debt (incl. current maturities)	9,034	—	8,677	—	8,677	8,076	—	7,338	1	7,339

IPL	2023					2022
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Money market fund investments	$45	$45	$—	$—	$45	$10	$10	$—	$—	$10
Commodity derivatives	54	—	30	24	54	138	—	111	27	138
Deferred proceeds	216	—	—	216	216	185	—	—	185	185
Liabilities and equity:
Commodity derivatives	30	—	25	5	30	46	—	35	11	46
Long-term debt (incl. current maturities)	3,945	—	3,664	—	3,664	3,646	—	3,228	—	3,228

WPL	2023					2022
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Commodity derivatives	$34	$—	$29	$5	$34	$99	$—	$95	$4	$99
Liabilities and equity:
Commodity derivatives	68	—	68	—	68	33	—	32	1	33
Long-term debt	3,070	—	2,933	—	2,933	2,770	—	2,542	—	2,542

Fair Value Measurements Using Significant Unobservable Inputs

Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net		Deferred Proceeds
	2023	2022	2023	2022
Beginning balance, January 1	$19	$29	$185	$214
Total net gains (losses) included in changes in net assets (realized/unrealized)	3	(18)	—	—
Purchases	62	79	—	—
Sales	(3)	(2)	—	—
Settlements (a)	(57)	(69)	31	(29)
Ending balance, December 31	$24	$19	$216	$185
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31	$3	($18)	$—	$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net		Deferred Proceeds
	2023	2022	2023	2022
Beginning balance, January 1	$16	$18	$185	$214
Total net losses included in changes in net assets (realized/unrealized)	(3)	(12)	—	—
Purchases	51	58	—	—
Sales	(3)	(1)	—	—
Settlements (a)	(42)	(47)	31	(29)
Ending balance, December 31	$19	$16	$216	$185
The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at December 31	($3)	($13)	$—	$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
	2023	2022
Beginning balance, January 1	$3	$11
Total net gains (losses) included in changes in net assets (realized/unrealized)	6	(6)
Purchases	11	21
Sales	—	(1)
Settlements (a)	(15)	(22)
Ending balance, December 31	$5	$3
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31	$6	($5)

(a)Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses associated with the receivables sold and cash amounts received from the receivables sold.

Fair Value Of Net Derivative Assets (Liabilities)

The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets (liabilities) at December 31 as follows (in millions):

	Alliant Energy		IPL		WPL
	Excluding FTRs	FTRs	Excluding FTRs	FTRs	Excluding FTRs	FTRs
2023	$3	$21	$3	$16	$—	$5
2022	(10)	29	(9)	25	(1)	4

IPL [Member]

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Recurring Fair Value Measurements

Carrying amounts and the related estimated fair values of other financial instruments at December 31 were as follows (in millions):

Alliant Energy	2023					2022
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Money market fund investments	$45	$45	$—	$—	$45	$10	$10	$—	$—	$10
Commodity derivatives	88	—	59	29	88	237	—	206	31	237
Interest rate derivatives	1	—	1	—	1	—	—	—	—	—
Deferred proceeds	216	—	—	216	216	185	—	—	185	185
Liabilities and equity:
Commodity derivatives	98	—	93	5	98	79	—	67	12	79
Long-term debt (incl. current maturities)	9,034	—	8,677	—	8,677	8,076	—	7,338	1	7,339

IPL	2023					2022
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Money market fund investments	$45	$45	$—	$—	$45	$10	$10	$—	$—	$10
Commodity derivatives	54	—	30	24	54	138	—	111	27	138
Deferred proceeds	216	—	—	216	216	185	—	—	185	185
Liabilities and equity:
Commodity derivatives	30	—	25	5	30	46	—	35	11	46
Long-term debt (incl. current maturities)	3,945	—	3,664	—	3,664	3,646	—	3,228	—	3,228

WPL	2023					2022
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Commodity derivatives	$34	$—	$29	$5	$34	$99	$—	$95	$4	$99
Liabilities and equity:
Commodity derivatives	68	—	68	—	68	33	—	32	1	33
Long-term debt	3,070	—	2,933	—	2,933	2,770	—	2,542	—	2,542

Fair Value Measurements Using Significant Unobservable Inputs

Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net		Deferred Proceeds
	2023	2022	2023	2022
Beginning balance, January 1	$19	$29	$185	$214
Total net gains (losses) included in changes in net assets (realized/unrealized)	3	(18)	—	—
Purchases	62	79	—	—
Sales	(3)	(2)	—	—
Settlements (a)	(57)	(69)	31	(29)
Ending balance, December 31	$24	$19	$216	$185
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31	$3	($18)	$—	$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net		Deferred Proceeds
	2023	2022	2023	2022
Beginning balance, January 1	$16	$18	$185	$214
Total net losses included in changes in net assets (realized/unrealized)	(3)	(12)	—	—
Purchases	51	58	—	—
Sales	(3)	(1)	—	—
Settlements (a)	(42)	(47)	31	(29)
Ending balance, December 31	$19	$16	$216	$185
The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at December 31	($3)	($13)	$—	$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
	2023	2022
Beginning balance, January 1	$3	$11
Total net gains (losses) included in changes in net assets (realized/unrealized)	6	(6)
Purchases	11	21
Sales	—	(1)
Settlements (a)	(15)	(22)
Ending balance, December 31	$5	$3
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31	$6	($5)

(a)Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses associated with the receivables sold and cash amounts received from the receivables sold.

Fair Value Of Net Derivative Assets (Liabilities)

The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets (liabilities) at December 31 as follows (in millions):

	Alliant Energy		IPL		WPL
	Excluding FTRs	FTRs	Excluding FTRs	FTRs	Excluding FTRs	FTRs
2023	$3	$21	$3	$16	$—	$5
2022	(10)	29	(9)	25	(1)	4

WPL [Member]

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Recurring Fair Value Measurements

Carrying amounts and the related estimated fair values of other financial instruments at December 31 were as follows (in millions):

Alliant Energy	2023					2022
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Money market fund investments	$45	$45	$—	$—	$45	$10	$10	$—	$—	$10
Commodity derivatives	88	—	59	29	88	237	—	206	31	237
Interest rate derivatives	1	—	1	—	1	—	—	—	—	—
Deferred proceeds	216	—	—	216	216	185	—	—	185	185
Liabilities and equity:
Commodity derivatives	98	—	93	5	98	79	—	67	12	79
Long-term debt (incl. current maturities)	9,034	—	8,677	—	8,677	8,076	—	7,338	1	7,339

IPL	2023					2022
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Money market fund investments	$45	$45	$—	$—	$45	$10	$10	$—	$—	$10
Commodity derivatives	54	—	30	24	54	138	—	111	27	138
Deferred proceeds	216	—	—	216	216	185	—	—	185	185
Liabilities and equity:
Commodity derivatives	30	—	25	5	30	46	—	35	11	46
Long-term debt (incl. current maturities)	3,945	—	3,664	—	3,664	3,646	—	3,228	—	3,228

WPL	2023					2022
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Commodity derivatives	$34	$—	$29	$5	$34	$99	$—	$95	$4	$99
Liabilities and equity:
Commodity derivatives	68	—	68	—	68	33	—	32	1	33
Long-term debt	3,070	—	2,933	—	2,933	2,770	—	2,542	—	2,542

Fair Value Measurements Using Significant Unobservable Inputs

Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net		Deferred Proceeds
	2023	2022	2023	2022
Beginning balance, January 1	$19	$29	$185	$214
Total net gains (losses) included in changes in net assets (realized/unrealized)	3	(18)	—	—
Purchases	62	79	—	—
Sales	(3)	(2)	—	—
Settlements (a)	(57)	(69)	31	(29)
Ending balance, December 31	$24	$19	$216	$185
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31	$3	($18)	$—	$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net		Deferred Proceeds
	2023	2022	2023	2022
Beginning balance, January 1	$16	$18	$185	$214
Total net losses included in changes in net assets (realized/unrealized)	(3)	(12)	—	—
Purchases	51	58	—	—
Sales	(3)	(1)	—	—
Settlements (a)	(42)	(47)	31	(29)
Ending balance, December 31	$19	$16	$216	$185
The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at December 31	($3)	($13)	$—	$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
	2023	2022
Beginning balance, January 1	$3	$11
Total net gains (losses) included in changes in net assets (realized/unrealized)	6	(6)
Purchases	11	21
Sales	—	(1)
Settlements (a)	(15)	(22)
Ending balance, December 31	$5	$3
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31	$6	($5)

(a)Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses associated with the receivables sold and cash amounts received from the receivables sold.

Fair Value Of Net Derivative Assets (Liabilities)

The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets (liabilities) at December 31 as follows (in millions):

	Alliant Energy		IPL		WPL
	Excluding FTRs	FTRs	Excluding FTRs	FTRs	Excluding FTRs	FTRs
2023	$3	$21	$3	$16	$—	$5
2022	(10)	29	(9)	25	(1)	4