Commitments And Contingencies (Tables)

12 Months Ended

Dec. 31, 2025

Long-term Purchase Commitment [Line Items]

Other Purchase Commitments

At December 31, 2025, the related minimum future commitments, excluding amounts for purchased power commitments that do not have minimum thresholds but require payment when electricity is generated by the provider and amounts for future commitments to deliver power to electric customers that do not have current minimum thresholds but will be billed for requirements when power is provided, were as follows (in millions):

Alliant Energy	2026	2027	2028	2029	2030	Thereafter	Total
Natural gas	$271	$191	$163	$145	$103	$245	$1,118
Coal	76	42	28	—	—	—	146
Other (a)	57	16	8	4	3	17	105
	$404	$249	$199	$149	$106	$262	$1,369

IPL	2026	2027	2028	2029	2030	Thereafter	Total
Natural gas	$149	$105	$85	$70	$31	$52	$492
Coal	34	14	10	—	—	—	58
Other (a)	24	2	2	2	2	16	48
	$207	$121	$97	$72	$33	$68	$598

WPL	2026	2027	2028	2029	2030	Thereafter	Total
Natural gas	$122	$86	$78	$75	$72	$193	$626
Coal	42	28	18	—	—	—	88
Other (a)	25	1	—	—	—	—	26
	$189	$115	$96	$75	$72	$193	$740

(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2025.

Schedule of Environmental Liabilities

At December 31, 2025, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions):

	Alliant Energy			IPL			WPL
Range of estimated future costs	$7	-	$29	$5	-	$18	$2	-	$11
Current and non-current environmental liabilities	$12			$8			$4

IPL [Member]

Long-term Purchase Commitment [Line Items]

Other Purchase Commitments

At December 31, 2025, the related minimum future commitments, excluding amounts for purchased power commitments that do not have minimum thresholds but require payment when electricity is generated by the provider and amounts for future commitments to deliver power to electric customers that do not have current minimum thresholds but will be billed for requirements when power is provided, were as follows (in millions):

Alliant Energy	2026	2027	2028	2029	2030	Thereafter	Total
Natural gas	$271	$191	$163	$145	$103	$245	$1,118
Coal	76	42	28	—	—	—	146
Other (a)	57	16	8	4	3	17	105
	$404	$249	$199	$149	$106	$262	$1,369

IPL	2026	2027	2028	2029	2030	Thereafter	Total
Natural gas	$149	$105	$85	$70	$31	$52	$492
Coal	34	14	10	—	—	—	58
Other (a)	24	2	2	2	2	16	48
	$207	$121	$97	$72	$33	$68	$598

WPL	2026	2027	2028	2029	2030	Thereafter	Total
Natural gas	$122	$86	$78	$75	$72	$193	$626
Coal	42	28	18	—	—	—	88
Other (a)	25	1	—	—	—	—	26
	$189	$115	$96	$75	$72	$193	$740

(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2025.

Schedule of Environmental Liabilities

At December 31, 2025, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions):

	Alliant Energy			IPL			WPL
Range of estimated future costs	$7	-	$29	$5	-	$18	$2	-	$11
Current and non-current environmental liabilities	$12			$8			$4

WPL [Member]

Long-term Purchase Commitment [Line Items]

Other Purchase Commitments

At December 31, 2025, the related minimum future commitments, excluding amounts for purchased power commitments that do not have minimum thresholds but require payment when electricity is generated by the provider and amounts for future commitments to deliver power to electric customers that do not have current minimum thresholds but will be billed for requirements when power is provided, were as follows (in millions):

Alliant Energy	2026	2027	2028	2029	2030	Thereafter	Total
Natural gas	$271	$191	$163	$145	$103	$245	$1,118
Coal	76	42	28	—	—	—	146
Other (a)	57	16	8	4	3	17	105
	$404	$249	$199	$149	$106	$262	$1,369

IPL	2026	2027	2028	2029	2030	Thereafter	Total
Natural gas	$149	$105	$85	$70	$31	$52	$492
Coal	34	14	10	—	—	—	58
Other (a)	24	2	2	2	2	16	48
	$207	$121	$97	$72	$33	$68	$598

WPL	2026	2027	2028	2029	2030	Thereafter	Total
Natural gas	$122	$86	$78	$75	$72	$193	$626
Coal	42	28	18	—	—	—	88
Other (a)	25	1	—	—	—	—	26
	$189	$115	$96	$75	$72	$193	$740

(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2025.

Schedule of Environmental Liabilities

At December 31, 2025, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions):

	Alliant Energy			IPL			WPL
Range of estimated future costs	$7	-	$29	$5	-	$18	$2	-	$11
Current and non-current environmental liabilities	$12			$8			$4