| Fiscal period | 2025 | 2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 |
|---|
| Period End Date | 12/31/2025 | 12/31/2024 | 12/31/2023 | 12/31/2022 | 12/31/2021 | 12/31/2020 | 12/31/2019 | 12/31/2018 | 12/31/2017 | 12/31/2016 |
|---|
| Utility: Gas | 525.00 | 465.00 | 540.00 | 642.00 | 456.00 | 373.00 | 455.20 | 446.60 | 400.90 | 355.40 |
| Utility: Electric | 3,697.00 | 3,372.00 | 3,345.00 | 3,421.00 | 3,081.00 | 2,920.00 | 3,063.60 | 3,000.30 | 2,894.70 | 2,875.50 |
| Utility: Other | 51.00 | 54.00 | 52.00 | 49.00 | 49.00 | 49.00 | 46.50 | 48.00 | 47.50 | 48.60 |
| Utility: Non-regulated | 89.00 | 90.00 | 90.00 | 93.00 | 83.00 | 74.00 | 82.40 | 39.60 | 39.10 | 40.50 |
| Total revenues | 4,362.00 | 3,981.00 | 4,027.00 | 4,205.00 | 3,669.00 | 3,416.00 | 3,647.70 | 3,534.50 | 3,382.20 | 3,320.00 |
| Cost of gas sold | 263.00 | 224.00 | 299.00 | 389.00 | 258.00 | 182.00 | 221.70 | 232.30 | 211.40 | 194.30 |
| Purchased power | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Electric production fuel and purchased power | 742.00 | 628.00 | 736.00 | 830.00 | 642.00 | 652.00 | 776.70 | 855.00 | 818.10 | 854.00 |
| Other operation and maintenance | 740.00 | 676.00 | 675.00 | 704.00 | 676.00 | 670.00 | -- | 645.80 | 651.00 | 606.50 |
| Other | -- | -- | -- | -- | -- | -- | 712.20 | -- | -- | -- |
| Non-regulated operation and maintenance | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Electric transmission service | 625.00 | 613.00 | 583.00 | 573.00 | 537.00 | 449.00 | 481.40 | 495.70 | 480.90 | 527.90 |
| Depreciation and amortization | 846.00 | 772.00 | 676.00 | 671.00 | 657.00 | 615.00 | 567.20 | 506.90 | 461.80 | 411.60 |
| Taxes other than income taxes | 121.00 | 122.00 | 115.00 | 110.00 | 104.00 | 108.00 | 110.80 | 104.40 | 105.60 | 102.30 |
| Asset valuation charges for Franklin County wind farm | -- | (60.00) | -- | -- | -- | -- | -- | -- | 0.00 | (86.40) |
| Total Operating Expenses | 3,337.00 | 3,095.00 | 3,084.00 | 3,277.00 | 2,874.00 | 2,676.00 | 2,870.00 | 2,840.10 | 2,728.80 | 2,783.00 |
| Operating income (loss) | 1,025.00 | 886.00 | 943.00 | 928.00 | 795.00 | 740.00 | 777.70 | 694.40 | 653.40 | 537.00 |
| Interest expense | 512.00 | 449.00 | 394.00 | 325.00 | 277.00 | 275.00 | 272.90 | 247.00 | 215.60 | 196.20 |
| Impairment of available-for-sale securities of McLeodUSA Inc | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Gain on sale of IPL"s electric transmission assets | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Gain on sale of Alliant Energy New Zealand Ltd. stock | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Preferred dividend requirements of subsidiaries | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Equity income from unconsolidated investments | 60.00 | 61.00 | 61.00 | 51.00 | 62.00 | 61.00 | 53.00 | 54.60 | 44.80 | 39.60 |
| Interest income and other | -- | -- | -- | -- | -- | -- | -- | -- | 0.50 | 0.50 |
| Interest income from loans to discontinued operations, net | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Allowance for funds used during construction | 89.00 | 75.00 | 100.00 | 60.00 | 25.00 | 55.00 | 92.70 | 75.60 | 49.70 | 62.50 |
| Other | (1.00) | 3.00 | (3.00) | (6.00) | (5.00) | (14.00) | (14.40) | (7.60) | -- | -- |
| Miscellaneous, net | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Loss on early extinguishment of debt | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Asset valuation charges - Brazil investments | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Pre-Tax Income | 661.00 | 576.00 | 707.00 | 708.00 | 600.00 | 567.00 | 636.10 | 570.00 | 532.80 | 443.40 |
| Income tax expense (benefit) | (149.00) | (114.00) | 4.00 | 22.00 | (74.00) | (57.00) | 68.70 | 47.70 | 66.70 | 59.40 |
| Current tax expense (benefit) : Federal | 10.00 | 13.00 | (3.00) | 7.00 | -- | -- | -- | -- | -- | 1.80 |
| Current tax expense (benefit) : State | (1.00) | (10.00) | (6.00) | 2.00 | -- | -- | -- | -- | -- | 17.20 |
| Deferred tax expense (benefit): Federal | 59.00 | 60.00 | 100.00 | 109.00 | -- | -- | -- | -- | -- | 112.80 |
| Deferred tax expense (benefit): State | 33.00 | 15.00 | 36.00 | 28.00 | -- | -- | -- | -- | -- | 4.90 |
| Foreign tax expense | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Research and development tax credits | (208.00) | (177.00) | -- | (123.00) | -- | -- | -- | -- | -- | (44.20) |
| Other tax credits | -- | -- | -- | (1.00) | -- | -- | -- | -- | -- | -- |
| Other Amortization of investment tax credits | (42.00) | (15.00) | -- | -- | -- | -- | -- | -- | -- | (1.30) |
| Oil, gas and alternative fuel credits | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Affordable housing tax credits | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Current tax expense (benefit): Nonconventional fuel credits | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Deferred tax expense (benefit Nonconventional fuel credits | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Provision recorded as a change in uncertain tax benefits | -- | -- | -- | -- | -- | -- | -- | -- | -- | (31.80) |
| Provision recorded as a change in accrued interest | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Income from continuing operations | -- | -- | -- | -- | -- | -- | 567.40 | 522.30 | 466.10 | 384.00 |
| Income (Loss) from Discontinued Operations, Net of Tax | -- | -- | -- | -- | -- | -- | -- | -- | 1.40 | (2.30) |
| Income (loss) before cumulative effect of changes in accounting principles | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Cumulative effect of changes in accounting principles | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Consolidated Net Income (Loss) | 810.00 | 690.00 | 703.00 | 686.00 | 674.00 | 624.00 | 567.40 | 522.30 | 467.50 | 381.70 |
| Preferred dividend requirements of subsidiaries | -- | -- | -- | -- | 15.00 | 10.00 | 10.20 | 10.20 | 10.20 | 10.20 |
| Net Income (Loss) Available to Common Shareholders | 810.00 | 690.00 | 703.00 | 686.00 | 659.00 | 614.00 | 557.20 | 512.10 | 457.30 | 371.50 |
| Earnings Per Share (Basic) - Cont Ops | -- | -- | -- | -- | -- | -- | -- | 2.19 | 1.99 | 1.65 |
| Earnings Per Share (Basic) - Disc Ops | -- | -- | -- | -- | -- | -- | -- | -- | -- | (0.01) |
| Earnings Per Share (Basic) - Acc Change | -- | -- | -- | -- | -- | -- | -- | 2.19 | -- | -- |
| NET EARNINGS PER SHARE (BASIC) | 3.15 | 2.69 | 2.78 | 2.73 | 2.63 | 2.47 | 2.34 | 2.19 | 1.99 | 1.64 |
| Earnings Per Share (Diluted) - Cont Ops | -- | -- | -- | -- | -- | -- | -- | 2.19 | 1.99 | 1.65 |
| Earnings Per Share (Diluted) - Disc Ops | -- | -- | -- | -- | -- | -- | -- | -- | -- | (0.01) |
| Earnings Per Share (Diluted) - Acc Change | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| NET EARNINGS PER SHARE (DILUTED) | 3.14 | 2.69 | 2.78 | 2.73 | 2.63 | 2.47 | 2.33 | 2.19 | 1.99 | 1.64 |
| Weighted Average Shares Outstanding (Basic) | 257.00 | 256.50 | 253.00 | 250.90 | 250.20 | 248.40 | 238.50 | 233.60 | 229.70 | 227.10 |
| Weighted Average Shares Outstanding (Diluted) | 257.80 | 256.80 | 253.30 | 251.20 | 250.70 | 248.70 | 239.00 | 233.60 | 229.70 | 227.10 |