Segments Of Business (Tables)

12 Months Ended

Dec. 31, 2025

Segment Reporting Information [Line Items]

Schedule of Segments of Business

Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s reportable segments, which represents the services provided to their customers, and reconciliation to consolidated amounts, was as follows (in millions):

	Utility
			Total		Alliant
			Reportable		Energy
2025	IPL	WPL	Segments	Other	Consolidated
Electric utility revenues	$1,896	$1,801	$3,697	N/A	$3,697
Gas utility revenues	265	260	525	N/A	525
Other revenues	47	4	51	$89	140
Total revenues	2,208	2,065	4,273	89	4,362
Electric production fuel and purchased power expense	283	459	742	N/A	742
Electric transmission service expense	422	203	625	N/A	625
Cost of gas sold expense	130	133	263	N/A	263
Other operation and maintenance expense (a)	373	306	679	61	740
Other segment items:
Depreciation and amortization expense	463	370	833	13	846
Interest expense	211	173	384	128	512
Equity income from unconsolidated investments, net	—	(2)	(2)	(58)	(60)
Income tax benefit	(127)	(14)	(141)	(8)	(149)
Other (b)	(4)	36	32	1	33
Net income (loss)	457	401	858	(48)	810
Total assets	12,495	10,655	23,150	1,841	24,991
Investments in equity method subsidiaries	5	19	24	650	674
Construction and acquisition expenditures	1,473	804	2,277	206	2,483

	Utility
			Total		Alliant
			Reportable		Energy
2024	IPL	WPL	Segments	Other	Consolidated
Electric utility revenues	$1,747	$1,625	$3,372	N/A	$3,372
Gas utility revenues	250	215	465	N/A	465
Other revenues	49	5	54	$90	144
Total revenues	2,046	1,845	3,891	90	3,981
Electric production fuel and purchased power expense	269	359	628	N/A	628
Electric transmission service expense	417	196	613	N/A	613
Cost of gas sold expense	123	101	224	N/A	224
Asset valuation charge for IPL’s Lansing Generating Station	60	—	60	N/A	60
Other operation and maintenance expense	358	279	637	39	676
Other segment items:
Depreciation and amortization expense	404	357	761	11	772
Interest expense	177	165	342	107	449
Equity income from unconsolidated investments, net	—	(2)	(2)	(59)	(61)
Income tax expense (benefit)	(129)	11	(118)	4	(114)
Other (b)	5	34	39	5	44
Net income (loss)	362	345	707	(17)	690
Total assets	11,407	10,106	21,513	1,201	22,714
Investments in equity method subsidiaries	5	17	22	601	623
Construction and acquisition expenditures	1,224	828	2,052	197	2,249

	Utility
			Total		Alliant
			Reportable		Energy
2023 (amounts may not foot due to rounding)	IPL	WPL	Segments	Other	Consolidated
Electric utility revenues	$1,761	$1,584	$3,345	N/A	$3,345
Gas utility revenues	300	240	540	N/A	540
Other revenues	49	3	52	$90	142
Total revenues	2,110	1,827	3,937	90	4,027
Electric production fuel and purchased power expense	282	455	737	N/A	736
Electric transmission service expense	420	163	583	N/A	583
Cost of gas sold expense	166	134	300	N/A	299
Other operation and maintenance expense	353	271	624	51	675
Other segment items:
Depreciation and amortization expense	388	280	668	8	676
Interest expense	155	149	304	90	394
Equity income from unconsolidated investments, net	—	(3)	(3)	(58)	(61)
Income tax expense (benefit)	(58)	60	2	2	4
Other (b)	38	(27)	11	5	18
Net income (loss)	366	345	711	(8)	703
Total assets	10,489	9,634	20,123	1,114	21,237
Investments in equity method subsidiaries	5	16	21	564	585
Construction and acquisition expenditures	712	1,019	1,731	123	1,854

(a)Alliant Energy’s non-utility holdings include Travero’s wind turbine blade recycling services, which commenced commercial operations in 2024, and whose assets are primarily included in “Property, plant and equipment, net” on Alliant Energy’s balance sheets. Alliant Energy suspended production of Travero’s wind turbine blade recycling services in November 2025 based on a review of strategic options, and as a result, a pre-tax non-cash asset valuation charge of $16 million was recorded to “Other operation and maintenance” in Alliant Energy’s income statement in 2025.

(b)Other segment items for each reportable segment include AFUDC, taxes other than income taxes, interest income, and other miscellaneous income and deductions.

IPL [Member]

Segment Reporting Information [Line Items]

Schedule of Segments of Business

Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s reportable segments, which represents the services provided to their customers, and reconciliation to consolidated amounts, was as follows (in millions):

	Utility
			Total		Alliant
			Reportable		Energy
2025	IPL	WPL	Segments	Other	Consolidated
Electric utility revenues	$1,896	$1,801	$3,697	N/A	$3,697
Gas utility revenues	265	260	525	N/A	525
Other revenues	47	4	51	$89	140
Total revenues	2,208	2,065	4,273	89	4,362
Electric production fuel and purchased power expense	283	459	742	N/A	742
Electric transmission service expense	422	203	625	N/A	625
Cost of gas sold expense	130	133	263	N/A	263
Other operation and maintenance expense (a)	373	306	679	61	740
Other segment items:
Depreciation and amortization expense	463	370	833	13	846
Interest expense	211	173	384	128	512
Equity income from unconsolidated investments, net	—	(2)	(2)	(58)	(60)
Income tax benefit	(127)	(14)	(141)	(8)	(149)
Other (b)	(4)	36	32	1	33
Net income (loss)	457	401	858	(48)	810
Total assets	12,495	10,655	23,150	1,841	24,991
Investments in equity method subsidiaries	5	19	24	650	674
Construction and acquisition expenditures	1,473	804	2,277	206	2,483

	Utility
			Total		Alliant
			Reportable		Energy
2024	IPL	WPL	Segments	Other	Consolidated
Electric utility revenues	$1,747	$1,625	$3,372	N/A	$3,372
Gas utility revenues	250	215	465	N/A	465
Other revenues	49	5	54	$90	144
Total revenues	2,046	1,845	3,891	90	3,981
Electric production fuel and purchased power expense	269	359	628	N/A	628
Electric transmission service expense	417	196	613	N/A	613
Cost of gas sold expense	123	101	224	N/A	224
Asset valuation charge for IPL’s Lansing Generating Station	60	—	60	N/A	60
Other operation and maintenance expense	358	279	637	39	676
Other segment items:
Depreciation and amortization expense	404	357	761	11	772
Interest expense	177	165	342	107	449
Equity income from unconsolidated investments, net	—	(2)	(2)	(59)	(61)
Income tax expense (benefit)	(129)	11	(118)	4	(114)
Other (b)	5	34	39	5	44
Net income (loss)	362	345	707	(17)	690
Total assets	11,407	10,106	21,513	1,201	22,714
Investments in equity method subsidiaries	5	17	22	601	623
Construction and acquisition expenditures	1,224	828	2,052	197	2,249

	Utility
			Total		Alliant
			Reportable		Energy
2023 (amounts may not foot due to rounding)	IPL	WPL	Segments	Other	Consolidated
Electric utility revenues	$1,761	$1,584	$3,345	N/A	$3,345
Gas utility revenues	300	240	540	N/A	540
Other revenues	49	3	52	$90	142
Total revenues	2,110	1,827	3,937	90	4,027
Electric production fuel and purchased power expense	282	455	737	N/A	736
Electric transmission service expense	420	163	583	N/A	583
Cost of gas sold expense	166	134	300	N/A	299
Other operation and maintenance expense	353	271	624	51	675
Other segment items:
Depreciation and amortization expense	388	280	668	8	676
Interest expense	155	149	304	90	394
Equity income from unconsolidated investments, net	—	(3)	(3)	(58)	(61)
Income tax expense (benefit)	(58)	60	2	2	4
Other (b)	38	(27)	11	5	18
Net income (loss)	366	345	711	(8)	703
Total assets	10,489	9,634	20,123	1,114	21,237
Investments in equity method subsidiaries	5	16	21	564	585
Construction and acquisition expenditures	712	1,019	1,731	123	1,854

(a)Alliant Energy’s non-utility holdings include Travero’s wind turbine blade recycling services, which commenced commercial operations in 2024, and whose assets are primarily included in “Property, plant and equipment, net” on Alliant Energy’s balance sheets. Alliant Energy suspended production of Travero’s wind turbine blade recycling services in November 2025 based on a review of strategic options, and as a result, a pre-tax non-cash asset valuation charge of $16 million was recorded to “Other operation and maintenance” in Alliant Energy’s income statement in 2025.

(b)Other segment items for each reportable segment include AFUDC, taxes other than income taxes, interest income, and other miscellaneous income and deductions.

WPL [Member]

Segment Reporting Information [Line Items]

Schedule of Segments of Business

Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s reportable segments, which represents the services provided to their customers, and reconciliation to consolidated amounts, was as follows (in millions):

	Utility
			Total		Alliant
			Reportable		Energy
2025	IPL	WPL	Segments	Other	Consolidated
Electric utility revenues	$1,896	$1,801	$3,697	N/A	$3,697
Gas utility revenues	265	260	525	N/A	525
Other revenues	47	4	51	$89	140
Total revenues	2,208	2,065	4,273	89	4,362
Electric production fuel and purchased power expense	283	459	742	N/A	742
Electric transmission service expense	422	203	625	N/A	625
Cost of gas sold expense	130	133	263	N/A	263
Other operation and maintenance expense (a)	373	306	679	61	740
Other segment items:
Depreciation and amortization expense	463	370	833	13	846
Interest expense	211	173	384	128	512
Equity income from unconsolidated investments, net	—	(2)	(2)	(58)	(60)
Income tax benefit	(127)	(14)	(141)	(8)	(149)
Other (b)	(4)	36	32	1	33
Net income (loss)	457	401	858	(48)	810
Total assets	12,495	10,655	23,150	1,841	24,991
Investments in equity method subsidiaries	5	19	24	650	674
Construction and acquisition expenditures	1,473	804	2,277	206	2,483

	Utility
			Total		Alliant
			Reportable		Energy
2024	IPL	WPL	Segments	Other	Consolidated
Electric utility revenues	$1,747	$1,625	$3,372	N/A	$3,372
Gas utility revenues	250	215	465	N/A	465
Other revenues	49	5	54	$90	144
Total revenues	2,046	1,845	3,891	90	3,981
Electric production fuel and purchased power expense	269	359	628	N/A	628
Electric transmission service expense	417	196	613	N/A	613
Cost of gas sold expense	123	101	224	N/A	224
Asset valuation charge for IPL’s Lansing Generating Station	60	—	60	N/A	60
Other operation and maintenance expense	358	279	637	39	676
Other segment items:
Depreciation and amortization expense	404	357	761	11	772
Interest expense	177	165	342	107	449
Equity income from unconsolidated investments, net	—	(2)	(2)	(59)	(61)
Income tax expense (benefit)	(129)	11	(118)	4	(114)
Other (b)	5	34	39	5	44
Net income (loss)	362	345	707	(17)	690
Total assets	11,407	10,106	21,513	1,201	22,714
Investments in equity method subsidiaries	5	17	22	601	623
Construction and acquisition expenditures	1,224	828	2,052	197	2,249

	Utility
			Total		Alliant
			Reportable		Energy
2023 (amounts may not foot due to rounding)	IPL	WPL	Segments	Other	Consolidated
Electric utility revenues	$1,761	$1,584	$3,345	N/A	$3,345
Gas utility revenues	300	240	540	N/A	540
Other revenues	49	3	52	$90	142
Total revenues	2,110	1,827	3,937	90	4,027
Electric production fuel and purchased power expense	282	455	737	N/A	736
Electric transmission service expense	420	163	583	N/A	583
Cost of gas sold expense	166	134	300	N/A	299
Other operation and maintenance expense	353	271	624	51	675
Other segment items:
Depreciation and amortization expense	388	280	668	8	676
Interest expense	155	149	304	90	394
Equity income from unconsolidated investments, net	—	(3)	(3)	(58)	(61)
Income tax expense (benefit)	(58)	60	2	2	4
Other (b)	38	(27)	11	5	18
Net income (loss)	366	345	711	(8)	703
Total assets	10,489	9,634	20,123	1,114	21,237
Investments in equity method subsidiaries	5	16	21	564	585
Construction and acquisition expenditures	712	1,019	1,731	123	1,854

(a)Alliant Energy’s non-utility holdings include Travero’s wind turbine blade recycling services, which commenced commercial operations in 2024, and whose assets are primarily included in “Property, plant and equipment, net” on Alliant Energy’s balance sheets. Alliant Energy suspended production of Travero’s wind turbine blade recycling services in November 2025 based on a review of strategic options, and as a result, a pre-tax non-cash asset valuation charge of $16 million was recorded to “Other operation and maintenance” in Alliant Energy’s income statement in 2025.

(b)Other segment items for each reportable segment include AFUDC, taxes other than income taxes, interest income, and other miscellaneous income and deductions.