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Investments | 12 Months Ended
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Dec. 31, 2025
Investments Disclosure [Abstract] |
Investments | Investme nts - MGE Energy and MGE. a. Equity Securities, Equity Method Investments, and Other Investments.
|  | MGE Energy |
(In thousands) |  | 2025 |  |  | 2024 |
Equity securities |  | $ | 22,591 |  |  | $ | 23,119 |
Equity method investments: |  |  |  |  |  |
ATC and ATC Holdco |  |  | 102,985 |  |  |  | 92,579 |
Other |  |  | 39 |  |  |  | 39 |
Total equity method investments |  |  | 103,024 |  |  |  | 92,618 |
Other investments |  |  | 2,298 |  |  |  | 2,298 |
Total |  | $ | 127,913 |  |  | $ | 118,035 |
Equity securities represent private equity investments in common stock of companies in various industries. MGE had no material investments in 2025 or 2024. For the years ended December 31, 2025, 2024, and 2023, there were no material liquidated investments for MGE. For the years ended December 31, 2025, 2024, and 2023, certain investments were liquidated for MGE Energy. As a result of these liquidations, the following was received:
(In thousands) |  | 2025 |  |  | 2024 |  |  | 2023 |
Cash proceeds |  | $ | 4,497 |  |  | $ | 2,554 |  |  | $ | 995 |
Gain (loss) on sale |  |  | 3,263 |  |  |  | 239 |  |  |  | (899 | )
b. ATC and ATC Holdco. ATC owns and operates electric transmission facilities primarily in Wisconsin. MGE received an interest in ATC when it, like other Wisconsin electric utilities, contributed its electric transmission facilities to ATC as required by Wisconsin law. That interest is presently held by MGE Transco, a subsidiary of MGE Energy. ATC Holdco was formed by several members of ATC, including MGE Energy, to pursue electric transmission development and investments outside of Wisconsin. The ownership interest in ATC Holdco is held by MGEE Transco, a subsidiary of MGE Energy. As of December 31, 2025 and 2024, MGE Transco held a 3.6% ownership interest in ATC. As of December 31, 2025 and 2024, MGEE Transco held a 4.4% ownership interest in ATC Holdco. MGE Transco and MGEE Transco have accounted for their investment in ATC and ATC Holdco, respectively, under the equity method of accounting. Equity earnings from investments are recorded as "Other income, net" on the consolidated statements of income of MGE Energy. For the following years ended December 31, MGE Transco recorded the following:
(In thousands) |  | 2025 |  |  | 2024 |  |  | 2023 |
Equity earnings from investment in ATC |  | $ | 12,682 |  |  | $ | 12,498 |  |  | $ | 10,515 |
Dividends received from ATC |  |  | 10,612 |  |  |  | 8,635 |  |  |  | 8,397 |
Capital contributions to ATC |  |  | 8,385 |  |  |  | 2,679 |  |  |  | 3,750 |
In January 2026, MGE Transco made a $4.5 million capital contribution to ATC. ATC Holdco was formed in December 2016. In 2025, 2024, and 2023 MGEE Transco recorded no capital contributions to ATC Holdco. ATC's summarized financial data is as follows:
(In thousands) |  |  |  |  |  |  |  |  |
Income statement data for the year ended December 31, |  | 2025 |  |  | 2024 |  |  | 2023 |
Operating revenues |  | $ | 974,956 |  |  | $ | 911,314 |  |  | $ | 818,921 |
Operating expenses |  |  | (472,610 | ) |  |  | (442,359 | ) |  |  | (407,643 | )
Other income |  |  | 1,364 |  |  |  | 1,407 |  |  |  | 2,452 |
Interest expense, net |  |  | (167,152 | ) |  |  | (139,204 | ) |  |  | (134,107 | )
Earnings before members' income taxes |  | $ | 336,558 |  |  | $ | 331,158 |  |  | $ | 279,623 |
Balance sheet data as of December 31, |  | 2025 |  |  | 2024 |  |  |  |
Current assets |  | $ | 137,522 |  |  | $ | 126,628 |  |  |  |
Noncurrent assets |  |  | 7,590,778 |  |  |  | 6,792,600 |  |  |  |
Total assets |  | $ | 7,728,300 |  |  | $ | 6,919,228 |  |  |  |
Current liabilities |  | $ | 839,789 |  |  | $ | 482,440 |  |  |  |
Long-term debt |  |  | 3,156,253 |  |  |  | 3,083,409 |  |  |  |
Other noncurrent liabilities |  |  | 638,916 |  |  |  | 544,973 |  |  |  |
Members' equity |  |  | 3,093,342 |  |  |  | 2,808,406 |  |  |  |
Total members' equity and liabilities |  | $ | 7,728,300 |  |  | $ | 6,919,228 |  |  |  |
MGE receives transmission and other related services from ATC. For the years ended December 31, 2025, 2024, and 2023, MGE recorded $40.8 million, $36.3 million, and $33.8 million, respectively, for transmission services received from ATC. MGE also provides a variety of operational, maintenance, and project management work for ATC, which is reimbursed by ATC. As of December 31, 2025 and 2024, MGE had a receivable due from ATC of $2.5 million and $2.0 million, respectively, related primarily to transmission interconnection at renewable solar and battery generation sites. MGE will be reimbursed for these costs after the new generation assets are placed into service.

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