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Derivative Instruments (Tables) | 9 Months Ended
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Sep. 30, 2025
Derivative Instruments [Line Items] |
Notional Amounts Of Derivative Instruments | As of September 30, 2025, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands):
| Electricity |  | FTRs |  | Natural Gas |  |  |  | Diesel Fuel
| MWhs |  | Years |  | MWhs |  | Years |  | Dths |  | Years |  |  |  |  |  | Gallons |  | Years
Alliant Energy | 1,689 |  |  | 2025-2026 |  | 17,992 |  |  | 2025-2026 |  | 136,910 |  |  | 2025-2032 |  |  |  |  |  | 630 |  |  | 2025
IPL | 563 |  |  | 2025-2026 |  | 7,143 |  |  | 2025-2026 |  | 56,355 |  |  | 2025-2030 |  |  |  |  |  | — |  |  | —
WPL | 1,126 |  |  | 2025-2026 |  | 10,849 |  |  | 2025-2026 |  | 80,555 |  |  | 2025-2032 |  |  |  |  |  | 630 |  |  | 2025
Fair Value Of Financial Instruments | Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2025 |  | December 31, 2024 |  | September 30, 2025 |  | December 31, 2024 |  | September 30, 2025 |  | December 31, 2024
Current derivative assets | $55 |  | $41 |  | $38 |  | $29 |  | $17 |  | $12
Non-current derivative assets | 27 |  | 34 |  | 14 |  | 19 |  | 13 |  | 15
Current derivative liabilities | 22 |  | 26 |  | 8 |  | 11 |  | 14 |  | 15
Non-current derivative liabilities | 26 |  | 32 |  | 2 |  | 2 |  | 24 |  | 30
Balance Sheet Offsetting | However, if the fair value amounts of derivative instruments by counterparty were netted, derivative assets and derivative liabilities related to commodity contracts would have been presented on the balance sheets as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| Gross |  |  |  | Gross |  |  |  | Gross |  |
| (as reported) |  | Net |  | (as reported) |  | Net |  | (as reported) |  | Net
September 30, 2025 |  |  |  |  |  |  |  |  |  |  |
Derivative assets | $82 |  | $72 |  | $52 |  | $47 |  | $30 |  | $25
Derivative liabilities | 48 |  | 38 |  | 10 |  | 5 |  | 38 |  | 33
December 31, 2024 |  |  |  |  |  |  |  |  |  |  |
Derivative assets | 75 |  | 64 |  | 48 |  | 43 |  | 27 |  | 21
Derivative liabilities | 58 |  | 47 |  | 13 |  | 8 |  | 45 |  | 39
IPL [Member] |
Derivative Instruments [Line Items] |
Notional Amounts Of Derivative Instruments | As of September 30, 2025, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands):
| Electricity |  | FTRs |  | Natural Gas |  |  |  | Diesel Fuel
| MWhs |  | Years |  | MWhs |  | Years |  | Dths |  | Years |  |  |  |  |  | Gallons |  | Years
Alliant Energy | 1,689 |  |  | 2025-2026 |  | 17,992 |  |  | 2025-2026 |  | 136,910 |  |  | 2025-2032 |  |  |  |  |  | 630 |  |  | 2025
IPL | 563 |  |  | 2025-2026 |  | 7,143 |  |  | 2025-2026 |  | 56,355 |  |  | 2025-2030 |  |  |  |  |  | — |  |  | —
WPL | 1,126 |  |  | 2025-2026 |  | 10,849 |  |  | 2025-2026 |  | 80,555 |  |  | 2025-2032 |  |  |  |  |  | 630 |  |  | 2025
Fair Value Of Financial Instruments | Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2025 |  | December 31, 2024 |  | September 30, 2025 |  | December 31, 2024 |  | September 30, 2025 |  | December 31, 2024
Current derivative assets | $55 |  | $41 |  | $38 |  | $29 |  | $17 |  | $12
Non-current derivative assets | 27 |  | 34 |  | 14 |  | 19 |  | 13 |  | 15
Current derivative liabilities | 22 |  | 26 |  | 8 |  | 11 |  | 14 |  | 15
Non-current derivative liabilities | 26 |  | 32 |  | 2 |  | 2 |  | 24 |  | 30
Balance Sheet Offsetting | However, if the fair value amounts of derivative instruments by counterparty were netted, derivative assets and derivative liabilities related to commodity contracts would have been presented on the balance sheets as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| Gross |  |  |  | Gross |  |  |  | Gross |  |
| (as reported) |  | Net |  | (as reported) |  | Net |  | (as reported) |  | Net
September 30, 2025 |  |  |  |  |  |  |  |  |  |  |
Derivative assets | $82 |  | $72 |  | $52 |  | $47 |  | $30 |  | $25
Derivative liabilities | 48 |  | 38 |  | 10 |  | 5 |  | 38 |  | 33
December 31, 2024 |  |  |  |  |  |  |  |  |  |  |
Derivative assets | 75 |  | 64 |  | 48 |  | 43 |  | 27 |  | 21
Derivative liabilities | 58 |  | 47 |  | 13 |  | 8 |  | 45 |  | 39
WPL [Member] |
Derivative Instruments [Line Items] |
Notional Amounts Of Derivative Instruments | As of September 30, 2025, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands):
| Electricity |  | FTRs |  | Natural Gas |  |  |  | Diesel Fuel
| MWhs |  | Years |  | MWhs |  | Years |  | Dths |  | Years |  |  |  |  |  | Gallons |  | Years
Alliant Energy | 1,689 |  |  | 2025-2026 |  | 17,992 |  |  | 2025-2026 |  | 136,910 |  |  | 2025-2032 |  |  |  |  |  | 630 |  |  | 2025
IPL | 563 |  |  | 2025-2026 |  | 7,143 |  |  | 2025-2026 |  | 56,355 |  |  | 2025-2030 |  |  |  |  |  | — |  |  | —
WPL | 1,126 |  |  | 2025-2026 |  | 10,849 |  |  | 2025-2026 |  | 80,555 |  |  | 2025-2032 |  |  |  |  |  | 630 |  |  | 2025
Fair Value Of Financial Instruments | Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2025 |  | December 31, 2024 |  | September 30, 2025 |  | December 31, 2024 |  | September 30, 2025 |  | December 31, 2024
Current derivative assets | $55 |  | $41 |  | $38 |  | $29 |  | $17 |  | $12
Non-current derivative assets | 27 |  | 34 |  | 14 |  | 19 |  | 13 |  | 15
Current derivative liabilities | 22 |  | 26 |  | 8 |  | 11 |  | 14 |  | 15
Non-current derivative liabilities | 26 |  | 32 |  | 2 |  | 2 |  | 24 |  | 30
Balance Sheet Offsetting | However, if the fair value amounts of derivative instruments by counterparty were netted, derivative assets and derivative liabilities related to commodity contracts would have been presented on the balance sheets as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| Gross |  |  |  | Gross |  |  |  | Gross |  |
| (as reported) |  | Net |  | (as reported) |  | Net |  | (as reported) |  | Net
September 30, 2025 |  |  |  |  |  |  |  |  |  |  |
Derivative assets | $82 |  | $72 |  | $52 |  | $47 |  | $30 |  | $25
Derivative liabilities | 48 |  | 38 |  | 10 |  | 5 |  | 38 |  | 33
December 31, 2024 |  |  |  |  |  |  |  |  |  |  |
Derivative assets | 75 |  | 64 |  | 48 |  | 43 |  | 27 |  | 21
Derivative liabilities | 58 |  | 47 |  | 13 |  | 8 |  | 45 |  | 39

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