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v3.26.1

Summary of Significant Accounting Principles (Details-1) - USD ($) $ in Thousands | 6 Months Ended |  |
--- | --- | --- | ---
Jun. 30, 2026 | Jun. 30, 2025 | Dec. 31, 2025 | Dec. 31, 2024
Supplemental Cash Flow Information [Abstract] |  |  |  |  |
US Federal | [1] | $ (7,232) | $ 3,681 |  |
Accrued capital expenditures |  | 26,099 | 9,120 |  |
Short-Term Debt [Abstract] |  |  |  |  |
Short-Term Debt |  | 34,750 |  | $ 94,527 |
Cash, Cash Equivalents, And Restricted Cash [Abstract] |  |  |  |  |
Cash and cash equivalents |  | 16,621 |  | 5,666 |
Restricted cash |  | 1,014 |  | 952 |
Receivable - margin account |  | 2,048 |  | 2,118 |
Cash, cash equivalents, and restricted cash |  | 19,683 | 13,136 | 8,736 | $ 24,496
Indemnification Agreement [Member] | Renewable Tax Credits Transferred [Member] |  |  |  |  |
Effects of The Inflation Reduction Act [Abstract] |  |  |  |  |
Guarantor Obligations, Liquidation Proceeds, Monetary Amount |  | 9,500 |  |  |
Wisconsin |  |  |  |  |
Supplemental Cash Flow Information [Abstract] |  |  |  |  |
US State and Local |  | 3,800 | 5,000 |  |
US State and Local - Other |  |  |  |  |
Supplemental Cash Flow Information [Abstract] |  |  |  |  |
US State and Local |  | 91 | 66 |  |
MGE [Member] |  |  |  |  |
Supplemental Cash Flow Information [Abstract] |  |  |  |  |
US Federal | [1],[2] | (7,872) | 3,351 |  |
Accrued capital expenditures | [2] | 26,099 | 9,120 |  |
Short-Term Debt [Abstract] |  |  |  |  |
Short-Term Debt |  | 34,750 |  | 94,527 |
Cash, Cash Equivalents, And Restricted Cash [Abstract] |  |  |  |  |
Cash and cash equivalents |  | 10,737 |  | 2,248 |
Restricted cash |  | 1,014 |  | 952 |
Receivable - margin account |  | 2,048 |  | 2,118 |
Cash, cash equivalents, and restricted cash |  | 13,799 | 6,092 | $ 5,318 | $ 20,059
MGE [Member] | Wisconsin |  |  |  |  |
Supplemental Cash Flow Information [Abstract] |  |  |  |  |
US State and Local | [2] | 3,620 | 4,980 |  |
MGE [Member] | US State and Local - Other |  |  |  |  |
Supplemental Cash Flow Information [Abstract] |  |  |  |  |
US State and Local | [2] | $ 0 | $ 0 |  |
[1] | For the six months ended June 30, 2026, federal tax receipts include $9.5 million of proceeds from the transfer of federal tax credits under Internal Revenue Code Section 6418.
[2] | 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.

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