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Summary of Significant Accounting Policies (Tables) | 12 Months Ended
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Dec. 31, 2025
Accounting Policies [Abstract] |
Supplemental Cash Flow Information |
|  | MGE Energy |  |  | MGE(b) |
(In Thousands) |  | 2025 |  |  | 2024 |  |  | 2023 |  |  | 2025 |  |  | 2024 |  |  | 2023 |
Interest Paid |  | $ | 35,755 |  |  | $ | 34,306 |  |  | $ | 29,526 |  |  | $ | 35,755 |  |  | $ | 34,306 |  |  | $ | 29,526 |
Income taxes paid (receipts), net(a): |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
US Federal |  |  | (3,970 | ) |  |  | (16,238 | ) |  |  | 4,000 |  |  |  | (5,750 | ) |  |  | (18,658 | ) |  |  | 3,450 |
US State and Local: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Wisconsin |  |  | 10,250 |  |  |  | 3,100 |  |  |  | 5,800 |  |  |  | 9,650 |  |  |  | 2,450 |  |  |  | 5,990 |
Other |  |  | 66 |  |  |  | 36 |  |  |  | — |  |  |  | — |  |  |  | — |  |  |  | — |
Significant noncash investing activities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accrued capital expenditures(c) |  |  | 55,283 |  |  |  | 22,734 |  |  |  | 17,247 |  |  |  | 55,283 |  |  |  | 22,734 |  |  |  | 17,247 |
(a) During the years ended December 31, 2025 and December 31, 2024, federal tax payments and receipts included proceeds from the transfer of PTCs under Internal Revenue Code Section 6418. Cash received for income taxes in 2025 includes $10.9 million related to PTCs generated in 2025 that were sold to a third party. Cash received for income taxes in 2024 includes $18.5 million related to PTCs generated in 2024 and 2023 that were sold to a third party. (b) MGE Energy files a consolidated federal income tax return with its subsidiaries. While taxes are filed on a consolidated basis, MGE calculates its respective share of tax liability and makes intercompany tax payments to or from its parent company. (c) Includes a $2.0 million unsecured promissory note, for an acquisition of land, issued to the seller, with all principal and interest paid in January 2026.
Cash, Cash Equivalents, and Restricted Cash | The following table presents components of cash flow, total cash, cash equivalents, and restricted cash on the consolidated balance sheets.
(In thousands) |  | MGE Energy |  |  | MGE |
As of December 31, |  | 2025 |  |  | 2024 |  |  | 2025 |  |  | 2024 |
Cash and cash equivalents |  | $ | 5,666 |  |  | $ | 21,302 |  |  | $ | 2,248 |  |  | $ | 16,865 |
Restricted cash |  |  | 952 |  |  |  | 1,113 |  |  |  | 952 |  |  |  | 1,113 |
Receivable - margin account |  |  | 2,118 |  |  |  | 2,081 |  |  |  | 2,118 |  |  |  | 2,081 |
Cash, cash equivalents, and restricted cash |  | $ | 8,736 |  |  | $ | 24,496 |  |  | $ | 5,318 |  |  | $ | 20,059 |
Straight-Line Depreciation Rates | Provisions at composite straight-line depreciation rates approximate the following percentages for the cost of depreciable property:
|  | 2025 |  | 2024 |  | 2023 |
Electric |  | 3.7 | % |  | 3.8 | % |  | 3.8 | %
Gas |  | 2.2 | % |  | 2.1 | % |  | 2.1 | %
Nonregulated |  | 2.3 | % |  | 2.3 | % |  | 2.3 | %
Approved AFUDC retail rates by rate case | For 2025, 2024, and 2023, as approved by the PSCW, MGE capitalized AFUDC-debt and equity on 50% of applicable average construction work in progress as shown in the following table:
|  | 2025 |  | 2024 |  | 2023 |
Approved AFUDC retail rates |  | 7.72 | % |  | 7.73 | % |  | 7.11 | %
Approved AFUDC-debt and equity capitalized amounts | For the years ended 2025, 2024, and 2023, MGE recorded AFUDC-debt and AFUDC-equity as shown in the following table:
(In millions) |  | 2025 |  | 2024 |  | 2023
AFUDC-debt |  | $ | 2.4 |  | $ | 2.2 |  | $ | 2.0
AFUDC-equity |  |  | 6.2 |  |  | 5.7 |  |  | 5.8

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