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Leases (Tables) | 12 Months Ended
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Dec. 31, 2024
Leases [Line Items] |
Schedule of Lease Details | Operating lease details are as follows (dollars in millions):
| December 31, 2024 |  | December 31, 2023
| Alliant Energy |  | IPL |  | WPL |  | Alliant Energy |  | IPL |  | WPL
Property, plant and equipment, net | $22 |  | $12 |  | $9 |  | $23 |  | $13 |  | $9
Other current liabilities | $2 |  | $1 |  | $1 |  | $2 |  | $1 |  | $1
Other liabilities | 20 |  | 11 |  | 8 |  | 21 |  | 12 |  | 8
Total operating lease liabilities | $22 |  | $12 |  | $9 |  | $23 |  | $13 |  | $9
Weighted average remaining lease term | 11 years |  | 11 years |  | 12 years |  | 12 years |  | 12 years |  | 12 years
Weighted average discount rate | 4% |  | 4% |  | 4% |  | 4% |  | 4% |  | 4%
Finance lease details are as follows (dollars in millions):
| December 31, 2024 |  | December 31, 2023
| Alliant Energy |  | IPL |  | WPL |  | Alliant Energy |  | IPL |  | WPL
Property, plant and equipment, net: |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility | N/A |  | N/A |  | $74 |  | N/A |  | N/A |  | $79
Leased land for solar generation | $189 |  | $53 |  | 136 |  | $172 |  | $33 |  | 139
| $189 |  | $53 |  | $210 |  | $172 |  | $33 |  | $218
Other current liabilities: |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility | N/A |  | N/A |  | $7 |  | N/A |  | N/A |  | $11
Leased land for solar generation | $— |  | $— |  | — |  | $— |  | $— |  | —
| — |  | — |  | 7 |  | — |  | — |  | 11
Other liabilities: |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility | N/A |  | N/A |  | 71 |  | N/A |  | N/A |  | 78
Leased land for solar generation | 189 |  | 53 |  | 136 |  | 172 |  | 33 |  | 139
| 189 |  | 53 |  | 207 |  | 172 |  | 33 |  | 217
Total finance lease liabilities | $189 |  | $53 |  | $214 |  | $172 |  | $33 |  | $228
Weighted average remaining lease term | 31 years |  | 28 years |  | 28 years |  | 33 years |  | 29 years |  | 27 years
Weighted average discount rate | 5% |  | 5% |  | 5% |  | 5% |  | 5% |  | 5%
| Alliant Energy |  | IPL |  | WPL
| 2024 |  | 2023 |  | 2022 |  | 2024 |  | 2023 |  | 2022 |  | 2024 |  | 2023 |  | 2022
Depreciation and amortization expenses | $— |  |  | $1 |  |  | $— |  |  | $— |  |  | $— |  |  | $— |  |  | $4 |  |  | $6 |  |  | $6 |
Interest expense | 8 |  |  | 6 |  |  | 3 |  |  | 2 |  |  | 1 |  |  | — |  |  | 10 |  |  | 8 |  |  | 7 |
Total finance lease expense | $8 |  |  | $7 |  |  | $3 |  |  | $2 |  |  | $1 |  |  | $— |  |  | $14 |  |  | $14 |  |  | $13 |
Finance lease liabilities arising from obtaining leased assets, which represent non-cash financing activities, were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2024 |  | 2023 |  |  |  | 2024 |  | 2023 |  |  |  | 2024 |  | 2023 |  |
Finance lease liabilities arising from obtaining leased assets | $20 |  |  | $34 |  |  |  |  | $20 |  |  | $33 |  |  |  |  | $— |  |  | $71 |  |  |
Schedule of Operating Lease Liability Maturities | As of December 31, 2024, expected maturities of lease liabilities were as follows (in millions):
| 2025 |  | 2026 |  | 2027 |  | 2028 |  | 2029 |  | Thereafter |  | Total |  | Less: amount representing interest |  | Present value of minimum lease payments
Operating Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy | $3 |  |  | $3 |  |  | $3 |  |  | $3 |  |  | $2 |  |  | $14 |  | $28 |  | $6 |  | $22
IPL | 2 |  |  | 2 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 8 |  | 15 |  | 3 |  | 12
WPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 7 |  | 12 |  | 3 |  | 9
Finance Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy | 9 |  |  | 9 |  |  | 9 |  |  | 10 |  |  | 10 |  |  | 337 |  | 384 |  | 195 |  | 189
IPL | 3 |  |  | 3 |  |  | 3 |  |  | 3 |  |  | 3 |  |  | 92 |  | 107 |  | 54 |  | 53
WPL | 17 |  |  | 13 |  |  | 13 |  |  | 13 |  |  | 13 |  |  | 324 |  | 393 |  | 179 |  | 214
Schedule of Finance Lease Liability Maturities | As of December 31, 2024, expected maturities of lease liabilities were as follows (in millions):
| 2025 |  | 2026 |  | 2027 |  | 2028 |  | 2029 |  | Thereafter |  | Total |  | Less: amount representing interest |  | Present value of minimum lease payments
Operating Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy | $3 |  |  | $3 |  |  | $3 |  |  | $3 |  |  | $2 |  |  | $14 |  | $28 |  | $6 |  | $22
IPL | 2 |  |  | 2 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 8 |  | 15 |  | 3 |  | 12
WPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 7 |  | 12 |  | 3 |  | 9
Finance Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy | 9 |  |  | 9 |  |  | 9 |  |  | 10 |  |  | 10 |  |  | 337 |  | 384 |  | 195 |  | 189
IPL | 3 |  |  | 3 |  |  | 3 |  |  | 3 |  |  | 3 |  |  | 92 |  | 107 |  | 54 |  | 53
WPL | 17 |  |  | 13 |  |  | 13 |  |  | 13 |  |  | 13 |  |  | 324 |  | 393 |  | 179 |  | 214
IPL [Member] |
Leases [Line Items] |
Schedule of Lease Details | Operating lease details are as follows (dollars in millions):
| December 31, 2024 |  | December 31, 2023
| Alliant Energy |  | IPL |  | WPL |  | Alliant Energy |  | IPL |  | WPL
Property, plant and equipment, net | $22 |  | $12 |  | $9 |  | $23 |  | $13 |  | $9
Other current liabilities | $2 |  | $1 |  | $1 |  | $2 |  | $1 |  | $1
Other liabilities | 20 |  | 11 |  | 8 |  | 21 |  | 12 |  | 8
Total operating lease liabilities | $22 |  | $12 |  | $9 |  | $23 |  | $13 |  | $9
Weighted average remaining lease term | 11 years |  | 11 years |  | 12 years |  | 12 years |  | 12 years |  | 12 years
Weighted average discount rate | 4% |  | 4% |  | 4% |  | 4% |  | 4% |  | 4%
Finance lease details are as follows (dollars in millions):
| December 31, 2024 |  | December 31, 2023
| Alliant Energy |  | IPL |  | WPL |  | Alliant Energy |  | IPL |  | WPL
Property, plant and equipment, net: |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility | N/A |  | N/A |  | $74 |  | N/A |  | N/A |  | $79
Leased land for solar generation | $189 |  | $53 |  | 136 |  | $172 |  | $33 |  | 139
| $189 |  | $53 |  | $210 |  | $172 |  | $33 |  | $218
Other current liabilities: |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility | N/A |  | N/A |  | $7 |  | N/A |  | N/A |  | $11
Leased land for solar generation | $— |  | $— |  | — |  | $— |  | $— |  | —
| — |  | — |  | 7 |  | — |  | — |  | 11
Other liabilities: |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility | N/A |  | N/A |  | 71 |  | N/A |  | N/A |  | 78
Leased land for solar generation | 189 |  | 53 |  | 136 |  | 172 |  | 33 |  | 139
| 189 |  | 53 |  | 207 |  | 172 |  | 33 |  | 217
Total finance lease liabilities | $189 |  | $53 |  | $214 |  | $172 |  | $33 |  | $228
Weighted average remaining lease term | 31 years |  | 28 years |  | 28 years |  | 33 years |  | 29 years |  | 27 years
Weighted average discount rate | 5% |  | 5% |  | 5% |  | 5% |  | 5% |  | 5%
| Alliant Energy |  | IPL |  | WPL
| 2024 |  | 2023 |  | 2022 |  | 2024 |  | 2023 |  | 2022 |  | 2024 |  | 2023 |  | 2022
Depreciation and amortization expenses | $— |  |  | $1 |  |  | $— |  |  | $— |  |  | $— |  |  | $— |  |  | $4 |  |  | $6 |  |  | $6 |
Interest expense | 8 |  |  | 6 |  |  | 3 |  |  | 2 |  |  | 1 |  |  | — |  |  | 10 |  |  | 8 |  |  | 7 |
Total finance lease expense | $8 |  |  | $7 |  |  | $3 |  |  | $2 |  |  | $1 |  |  | $— |  |  | $14 |  |  | $14 |  |  | $13 |
Finance lease liabilities arising from obtaining leased assets, which represent non-cash financing activities, were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2024 |  | 2023 |  |  |  | 2024 |  | 2023 |  |  |  | 2024 |  | 2023 |  |
Finance lease liabilities arising from obtaining leased assets | $20 |  |  | $34 |  |  |  |  | $20 |  |  | $33 |  |  |  |  | $— |  |  | $71 |  |  |
Schedule of Operating Lease Liability Maturities | As of December 31, 2024, expected maturities of lease liabilities were as follows (in millions):
| 2025 |  | 2026 |  | 2027 |  | 2028 |  | 2029 |  | Thereafter |  | Total |  | Less: amount representing interest |  | Present value of minimum lease payments
Operating Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy | $3 |  |  | $3 |  |  | $3 |  |  | $3 |  |  | $2 |  |  | $14 |  | $28 |  | $6 |  | $22
IPL | 2 |  |  | 2 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 8 |  | 15 |  | 3 |  | 12
WPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 7 |  | 12 |  | 3 |  | 9
Finance Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy | 9 |  |  | 9 |  |  | 9 |  |  | 10 |  |  | 10 |  |  | 337 |  | 384 |  | 195 |  | 189
IPL | 3 |  |  | 3 |  |  | 3 |  |  | 3 |  |  | 3 |  |  | 92 |  | 107 |  | 54 |  | 53
WPL | 17 |  |  | 13 |  |  | 13 |  |  | 13 |  |  | 13 |  |  | 324 |  | 393 |  | 179 |  | 214
Schedule of Finance Lease Liability Maturities | As of December 31, 2024, expected maturities of lease liabilities were as follows (in millions):
| 2025 |  | 2026 |  | 2027 |  | 2028 |  | 2029 |  | Thereafter |  | Total |  | Less: amount representing interest |  | Present value of minimum lease payments
Operating Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy | $3 |  |  | $3 |  |  | $3 |  |  | $3 |  |  | $2 |  |  | $14 |  | $28 |  | $6 |  | $22
IPL | 2 |  |  | 2 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 8 |  | 15 |  | 3 |  | 12
WPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 7 |  | 12 |  | 3 |  | 9
Finance Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy | 9 |  |  | 9 |  |  | 9 |  |  | 10 |  |  | 10 |  |  | 337 |  | 384 |  | 195 |  | 189
IPL | 3 |  |  | 3 |  |  | 3 |  |  | 3 |  |  | 3 |  |  | 92 |  | 107 |  | 54 |  | 53
WPL | 17 |  |  | 13 |  |  | 13 |  |  | 13 |  |  | 13 |  |  | 324 |  | 393 |  | 179 |  | 214
WPL [Member] |
Leases [Line Items] |
Schedule of Lease Details | Operating lease details are as follows (dollars in millions):
| December 31, 2024 |  | December 31, 2023
| Alliant Energy |  | IPL |  | WPL |  | Alliant Energy |  | IPL |  | WPL
Property, plant and equipment, net | $22 |  | $12 |  | $9 |  | $23 |  | $13 |  | $9
Other current liabilities | $2 |  | $1 |  | $1 |  | $2 |  | $1 |  | $1
Other liabilities | 20 |  | 11 |  | 8 |  | 21 |  | 12 |  | 8
Total operating lease liabilities | $22 |  | $12 |  | $9 |  | $23 |  | $13 |  | $9
Weighted average remaining lease term | 11 years |  | 11 years |  | 12 years |  | 12 years |  | 12 years |  | 12 years
Weighted average discount rate | 4% |  | 4% |  | 4% |  | 4% |  | 4% |  | 4%
Finance lease details are as follows (dollars in millions):
| December 31, 2024 |  | December 31, 2023
| Alliant Energy |  | IPL |  | WPL |  | Alliant Energy |  | IPL |  | WPL
Property, plant and equipment, net: |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility | N/A |  | N/A |  | $74 |  | N/A |  | N/A |  | $79
Leased land for solar generation | $189 |  | $53 |  | 136 |  | $172 |  | $33 |  | 139
| $189 |  | $53 |  | $210 |  | $172 |  | $33 |  | $218
Other current liabilities: |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility | N/A |  | N/A |  | $7 |  | N/A |  | N/A |  | $11
Leased land for solar generation | $— |  | $— |  | — |  | $— |  | $— |  | —
| — |  | — |  | 7 |  | — |  | — |  | 11
Other liabilities: |  |  |  |  |  |  |  |  |  |  |
Sheboygan Falls Energy Facility | N/A |  | N/A |  | 71 |  | N/A |  | N/A |  | 78
Leased land for solar generation | 189 |  | 53 |  | 136 |  | 172 |  | 33 |  | 139
| 189 |  | 53 |  | 207 |  | 172 |  | 33 |  | 217
Total finance lease liabilities | $189 |  | $53 |  | $214 |  | $172 |  | $33 |  | $228
Weighted average remaining lease term | 31 years |  | 28 years |  | 28 years |  | 33 years |  | 29 years |  | 27 years
Weighted average discount rate | 5% |  | 5% |  | 5% |  | 5% |  | 5% |  | 5%
| Alliant Energy |  | IPL |  | WPL
| 2024 |  | 2023 |  | 2022 |  | 2024 |  | 2023 |  | 2022 |  | 2024 |  | 2023 |  | 2022
Depreciation and amortization expenses | $— |  |  | $1 |  |  | $— |  |  | $— |  |  | $— |  |  | $— |  |  | $4 |  |  | $6 |  |  | $6 |
Interest expense | 8 |  |  | 6 |  |  | 3 |  |  | 2 |  |  | 1 |  |  | — |  |  | 10 |  |  | 8 |  |  | 7 |
Total finance lease expense | $8 |  |  | $7 |  |  | $3 |  |  | $2 |  |  | $1 |  |  | $— |  |  | $14 |  |  | $14 |  |  | $13 |
Finance lease liabilities arising from obtaining leased assets, which represent non-cash financing activities, were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2024 |  | 2023 |  |  |  | 2024 |  | 2023 |  |  |  | 2024 |  | 2023 |  |
Finance lease liabilities arising from obtaining leased assets | $20 |  |  | $34 |  |  |  |  | $20 |  |  | $33 |  |  |  |  | $— |  |  | $71 |  |  |
Schedule of Operating Lease Liability Maturities | As of December 31, 2024, expected maturities of lease liabilities were as follows (in millions):
| 2025 |  | 2026 |  | 2027 |  | 2028 |  | 2029 |  | Thereafter |  | Total |  | Less: amount representing interest |  | Present value of minimum lease payments
Operating Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy | $3 |  |  | $3 |  |  | $3 |  |  | $3 |  |  | $2 |  |  | $14 |  | $28 |  | $6 |  | $22
IPL | 2 |  |  | 2 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 8 |  | 15 |  | 3 |  | 12
WPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 7 |  | 12 |  | 3 |  | 9
Finance Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy | 9 |  |  | 9 |  |  | 9 |  |  | 10 |  |  | 10 |  |  | 337 |  | 384 |  | 195 |  | 189
IPL | 3 |  |  | 3 |  |  | 3 |  |  | 3 |  |  | 3 |  |  | 92 |  | 107 |  | 54 |  | 53
WPL | 17 |  |  | 13 |  |  | 13 |  |  | 13 |  |  | 13 |  |  | 324 |  | 393 |  | 179 |  | 214
Schedule of Finance Lease Liability Maturities | As of December 31, 2024, expected maturities of lease liabilities were as follows (in millions):
| 2025 |  | 2026 |  | 2027 |  | 2028 |  | 2029 |  | Thereafter |  | Total |  | Less: amount representing interest |  | Present value of minimum lease payments
Operating Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy | $3 |  |  | $3 |  |  | $3 |  |  | $3 |  |  | $2 |  |  | $14 |  | $28 |  | $6 |  | $22
IPL | 2 |  |  | 2 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 8 |  | 15 |  | 3 |  | 12
WPL | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 1 |  |  | 7 |  | 12 |  | 3 |  | 9
Finance Leases: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Alliant Energy | 9 |  |  | 9 |  |  | 9 |  |  | 10 |  |  | 10 |  |  | 337 |  | 384 |  | 195 |  | 189
IPL | 3 |  |  | 3 |  |  | 3 |  |  | 3 |  |  | 3 |  |  | 92 |  | 107 |  | 54 |  | 53
WPL | 17 |  |  | 13 |  |  | 13 |  |  | 13 |  |  | 13 |  |  | 324 |  | 393 |  | 179 |  | 214

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