Leases (Tables)

12 Months Ended

Dec. 31, 2023

Leases [Line Items]

Schedule of Lease Details

Operating lease details are as follows (dollars in millions):

	December 31, 2023			December 31, 2022
	Alliant Energy	IPL	WPL	Alliant Energy	IPL	WPL
Property, plant and equipment, net	$23	$13	$9	$16	$9	$6
Other current liabilities	$2	$1	$1	$3	$1	$1
Other liabilities	21	12	8	13	8	5
Total operating lease liabilities	$23	$13	$9	$16	$9	$6
Weighted average remaining lease term	12 years	12 years	12 years	10 years	11 years	9 years
Weighted average discount rate	4%	4%	4%	4%	4%	4%

Finance lease details are as follows (dollars in millions):

	December 31, 2023			December 31, 2022
	Alliant Energy	IPL	WPL	Alliant Energy	IPL	WPL
Property, plant and equipment, net:
Sheboygan Falls Energy Facility	N/A	N/A	$79	N/A	N/A	$15
Leased land for solar generation	$172	$33	139	$133	$—	133
	$172	$33	$218	$133	$—	$148
Other current liabilities:
Sheboygan Falls Energy Facility	N/A	N/A	$11	N/A	N/A	$12
Leased land for solar generation	$—	$—	—	$5	$—	5
	—	—	11	5	—	17
Other liabilities:
Sheboygan Falls Energy Facility	N/A	N/A	78	N/A	N/A	19
Leased land for solar generation	172	33	139	131	—	131
	172	33	217	131	—	150
Total finance lease liabilities	$172	$33	$228	$136	$—	$167
Weighted average remaining lease term	33 years	29 years	27 years	34 years	N/A	28 years
Weighted average discount rate	5%	5%	5%	5%	N/A	5%

	Alliant Energy			IPL			WPL
	2023	2022	2021	2023	2022	2021	2023	2022	2021
Depreciation and amortization expenses	$1	$—	$—	$—	$—	$—	$6	$6	$6
Interest expense	6	3	—	1	—	—	8	7	5
Total finance lease expense	$7	$3	$—	$1	$—	$—	$14	$13	$11

Finance lease liabilities arising from obtaining leased assets, which represent non-cash financing activities, were as follows (in millions):

	Alliant Energy		IPL		WPL
	2023	2022	2023	2022	2023	2022
Finance lease liabilities arising from obtaining leased assets	$34	$125	$33	$—	$71	$125

Schedule of Operating Lease Liability Maturities

As of December 31, 2023, expected maturities of lease liabilities were as follows (in millions):

	2024	2025	2026	2027	2028	Thereafter	Total	Less: amount representing interest	Present value of minimum lease payments
Operating Leases:
Alliant Energy	$3	$3	$3	$3	$2	$16	$30	$7	$23
IPL	1	2	2	1	1	10	17	4	13
WPL	2	1	1	1	1	6	12	3	9
Finance Leases:
Alliant Energy	8	8	8	8	8	320	360	188	172
IPL	2	2	2	2	2	59	69	36	33
WPL	21	17	13	13	13	334	411	183	228

Schedule of Finance Lease Liability Maturities

As of December 31, 2023, expected maturities of lease liabilities were as follows (in millions):

	2024	2025	2026	2027	2028	Thereafter	Total	Less: amount representing interest	Present value of minimum lease payments
Operating Leases:
Alliant Energy	$3	$3	$3	$3	$2	$16	$30	$7	$23
IPL	1	2	2	1	1	10	17	4	13
WPL	2	1	1	1	1	6	12	3	9
Finance Leases:
Alliant Energy	8	8	8	8	8	320	360	188	172
IPL	2	2	2	2	2	59	69	36	33
WPL	21	17	13	13	13	334	411	183	228

IPL [Member]

Leases [Line Items]

Schedule of Lease Details

Operating lease details are as follows (dollars in millions):

	December 31, 2023			December 31, 2022
	Alliant Energy	IPL	WPL	Alliant Energy	IPL	WPL
Property, plant and equipment, net	$23	$13	$9	$16	$9	$6
Other current liabilities	$2	$1	$1	$3	$1	$1
Other liabilities	21	12	8	13	8	5
Total operating lease liabilities	$23	$13	$9	$16	$9	$6
Weighted average remaining lease term	12 years	12 years	12 years	10 years	11 years	9 years
Weighted average discount rate	4%	4%	4%	4%	4%	4%

Finance lease details are as follows (dollars in millions):

	December 31, 2023			December 31, 2022
	Alliant Energy	IPL	WPL	Alliant Energy	IPL	WPL
Property, plant and equipment, net:
Sheboygan Falls Energy Facility	N/A	N/A	$79	N/A	N/A	$15
Leased land for solar generation	$172	$33	139	$133	$—	133
	$172	$33	$218	$133	$—	$148
Other current liabilities:
Sheboygan Falls Energy Facility	N/A	N/A	$11	N/A	N/A	$12
Leased land for solar generation	$—	$—	—	$5	$—	5
	—	—	11	5	—	17
Other liabilities:
Sheboygan Falls Energy Facility	N/A	N/A	78	N/A	N/A	19
Leased land for solar generation	172	33	139	131	—	131
	172	33	217	131	—	150
Total finance lease liabilities	$172	$33	$228	$136	$—	$167
Weighted average remaining lease term	33 years	29 years	27 years	34 years	N/A	28 years
Weighted average discount rate	5%	5%	5%	5%	N/A	5%

	Alliant Energy			IPL			WPL
	2023	2022	2021	2023	2022	2021	2023	2022	2021
Depreciation and amortization expenses	$1	$—	$—	$—	$—	$—	$6	$6	$6
Interest expense	6	3	—	1	—	—	8	7	5
Total finance lease expense	$7	$3	$—	$1	$—	$—	$14	$13	$11

Finance lease liabilities arising from obtaining leased assets, which represent non-cash financing activities, were as follows (in millions):

	Alliant Energy		IPL		WPL
	2023	2022	2023	2022	2023	2022
Finance lease liabilities arising from obtaining leased assets	$34	$125	$33	$—	$71	$125

Schedule of Operating Lease Liability Maturities

As of December 31, 2023, expected maturities of lease liabilities were as follows (in millions):

	2024	2025	2026	2027	2028	Thereafter	Total	Less: amount representing interest	Present value of minimum lease payments
Operating Leases:
Alliant Energy	$3	$3	$3	$3	$2	$16	$30	$7	$23
IPL	1	2	2	1	1	10	17	4	13
WPL	2	1	1	1	1	6	12	3	9
Finance Leases:
Alliant Energy	8	8	8	8	8	320	360	188	172
IPL	2	2	2	2	2	59	69	36	33
WPL	21	17	13	13	13	334	411	183	228

Schedule of Finance Lease Liability Maturities

As of December 31, 2023, expected maturities of lease liabilities were as follows (in millions):

	2024	2025	2026	2027	2028	Thereafter	Total	Less: amount representing interest	Present value of minimum lease payments
Operating Leases:
Alliant Energy	$3	$3	$3	$3	$2	$16	$30	$7	$23
IPL	1	2	2	1	1	10	17	4	13
WPL	2	1	1	1	1	6	12	3	9
Finance Leases:
Alliant Energy	8	8	8	8	8	320	360	188	172
IPL	2	2	2	2	2	59	69	36	33
WPL	21	17	13	13	13	334	411	183	228

WPL [Member]

Leases [Line Items]

Schedule of Lease Details

Operating lease details are as follows (dollars in millions):

	December 31, 2023			December 31, 2022
	Alliant Energy	IPL	WPL	Alliant Energy	IPL	WPL
Property, plant and equipment, net	$23	$13	$9	$16	$9	$6
Other current liabilities	$2	$1	$1	$3	$1	$1
Other liabilities	21	12	8	13	8	5
Total operating lease liabilities	$23	$13	$9	$16	$9	$6
Weighted average remaining lease term	12 years	12 years	12 years	10 years	11 years	9 years
Weighted average discount rate	4%	4%	4%	4%	4%	4%

Finance lease details are as follows (dollars in millions):

	December 31, 2023			December 31, 2022
	Alliant Energy	IPL	WPL	Alliant Energy	IPL	WPL
Property, plant and equipment, net:
Sheboygan Falls Energy Facility	N/A	N/A	$79	N/A	N/A	$15
Leased land for solar generation	$172	$33	139	$133	$—	133
	$172	$33	$218	$133	$—	$148
Other current liabilities:
Sheboygan Falls Energy Facility	N/A	N/A	$11	N/A	N/A	$12
Leased land for solar generation	$—	$—	—	$5	$—	5
	—	—	11	5	—	17
Other liabilities:
Sheboygan Falls Energy Facility	N/A	N/A	78	N/A	N/A	19
Leased land for solar generation	172	33	139	131	—	131
	172	33	217	131	—	150
Total finance lease liabilities	$172	$33	$228	$136	$—	$167
Weighted average remaining lease term	33 years	29 years	27 years	34 years	N/A	28 years
Weighted average discount rate	5%	5%	5%	5%	N/A	5%

	Alliant Energy			IPL			WPL
	2023	2022	2021	2023	2022	2021	2023	2022	2021
Depreciation and amortization expenses	$1	$—	$—	$—	$—	$—	$6	$6	$6
Interest expense	6	3	—	1	—	—	8	7	5
Total finance lease expense	$7	$3	$—	$1	$—	$—	$14	$13	$11

Finance lease liabilities arising from obtaining leased assets, which represent non-cash financing activities, were as follows (in millions):

	Alliant Energy		IPL		WPL
	2023	2022	2023	2022	2023	2022
Finance lease liabilities arising from obtaining leased assets	$34	$125	$33	$—	$71	$125

Schedule of Operating Lease Liability Maturities

As of December 31, 2023, expected maturities of lease liabilities were as follows (in millions):

	2024	2025	2026	2027	2028	Thereafter	Total	Less: amount representing interest	Present value of minimum lease payments
Operating Leases:
Alliant Energy	$3	$3	$3	$3	$2	$16	$30	$7	$23
IPL	1	2	2	1	1	10	17	4	13
WPL	2	1	1	1	1	6	12	3	9
Finance Leases:
Alliant Energy	8	8	8	8	8	320	360	188	172
IPL	2	2	2	2	2	59	69	36	33
WPL	21	17	13	13	13	334	411	183	228

Schedule of Finance Lease Liability Maturities

As of December 31, 2023, expected maturities of lease liabilities were as follows (in millions):

	2024	2025	2026	2027	2028	Thereafter	Total	Less: amount representing interest	Present value of minimum lease payments
Operating Leases:
Alliant Energy	$3	$3	$3	$3	$2	$16	$30	$7	$23
IPL	1	2	2	1	1	10	17	4	13
WPL	2	1	1	1	1	6	12	3	9
Finance Leases:
Alliant Energy	8	8	8	8	8	320	360	188	172
IPL	2	2	2	2	2	59	69	36	33
WPL	21	17	13	13	13	334	411	183	228