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Long-Term Debt (Tables) | 12 Months Ended
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Dec. 31, 2025
Debt Disclosure [Abstract] |
Schedule of Long-Term Debt |
|  | December 31, |
(In thousands) |  | 2025 |  |  | 2024 |
First Mortgage Bonds:(a) |  |  |  |  |  |
7.70%, 2028 Series |  | $ | 1,200 |  |  | $ | 1,200 |
Tax Exempt Debt: |  |  |  |  |  |
3.75%, 2027 Series, Industrial Development Revenue Bonds |  |  | 19,300 |  |  |  | 19,300 |
Medium-Term Notes:(b) |  |  |  |  |  |
6.12%, due 2028 |  |  | 20,000 |  |  |  | 20,000 |
7.12%, due 2032 |  |  | 25,000 |  |  |  | 25,000 |
6.247%, due 2037 |  |  | 25,000 |  |  |  | 25,000 |
Total Medium-Term Notes |  |  | 70,000 |  |  |  | 70,000 |
Other Long-Term Debt:(c) |  |  |  |  |  |
3.29%, due 2026(d) |  |  | 15,000 |  |  |  | 15,000 |
3.11%, due 2027(d) |  |  | 30,000 |  |  |  | 30,000 |
2.94%, due 2029(d) |  |  | 50,000 |  |  |  | 50,000 |
2.48%, due 2031(d) |  |  | 60,000 |  |  |  | 60,000 |
5.43%, due 2032(d) |  |  | 25,000 |  |  |  | 25,000 |
5.43%, due 2033(d) |  |  | 15,000 |  |  |  | 15,000 |
5.68%, due 2033(e) |  |  | 15,726 |  |  |  | 17,297 |
5.19%, due 2033(e) |  |  | 10,250 |  |  |  | 11,298 |
2.63%, due 2033(d) |  |  | 40,000 |  |  |  | 40,000 |
5.61%, due 2034(d) |  |  | 40,000 |  |  |  | 40,000 |
5.53%, due 2035(d) |  |  | 35,000 |  |  |  | 35,000 |
5.12%, due 2036(d)(f) |  |  | 25,000 |  |  |  | — |
5.30%, due 2039(d) |  |  | 25,000 |  |  |  | 25,000 |
5.26%, due 2040(d) |  |  | 15,000 |  |  |  | 15,000 |
5.04%, due 2040(g) |  |  | 23,472 |  |  |  | 25,139 |
4.74%, due 2041(g) |  |  | 15,167 |  |  |  | 16,167 |
4.38%, due 2042(d) |  |  | 28,000 |  |  |  | 28,000 |
4.42%, due 2043(d) |  |  | 20,000 |  |  |  | 20,000 |
4.47%, due 2048(d) |  |  | 20,000 |  |  |  | 20,000 |
4.19%, due 2048(d) |  |  | 60,000 |  |  |  | 60,000 |
3.76%, due 2052(d) |  |  | 40,000 |  |  |  | 40,000 |
4.24%, due 2053(d) |  |  | 20,000 |  |  |  | 20,000 |
5.91%, due 2053(d) |  |  | 30,000 |  |  |  | 30,000 |
5.59%, due 2054(d) |  |  | 25,000 |  |  |  | 25,000 |
5.76%, due 2055(d)(f) |  |  | 25,000 |  |  |  | — |
4.34%, due 2058(d) |  |  | 20,000 |  |  |  | 20,000 |
Total Other Long-Term Debt |  |  | 727,615 |  |  |  | 682,901 |
Long-term debt due within one year |  |  | (21,633 | ) |  |  | (5,285 | )
Unamortized discount and debt issuance costs |  |  | (4,277 | ) |  |  | (4,419 | )
Total Long-Term Debt |  | $ | 792,205 |  |  | $ | 763,697 |
(a) MGE's utility plant was subject to a lien related to its Indenture of Mortgage and Deed of Trust, under which its first mortgage bonds were issued. On January 27, 2026, MGE completed a redemption of all outstanding first mortgage bonds and delivered to the Trustee a satisfaction and discharge which, pursuant to the terms of the Indenture, effectively discharged the Indenture. The Mortgage Indenture provided that dividends or any other distribution or purchase of MGE shares may not be made if the aggregate amount thereof since December 31, 1945, would exceed the earned surplus (retained earnings) accumulated subsequent to December 31, 1945. As of December 31, 2025, approximately $807.2 million was available for the payment of dividends under this covenant. (b) The indenture under which MGE's Medium-Term notes are issued provides that those notes will be entitled to be equally and ratably secured in the event that MGE issues any additional secured bonds. (c) Unsecured notes issued pursuant to various Note Purchase Agreements with one or more purchasers. The notes are not issued under, or governed by, MGE's Indenture dated as of September 1, 1998, which governs MGE's Medium-Term Notes. (d) Issued by MGE. Under that Note Purchase Agreement: (i) note holders have the right to require MGE to repurchase their notes at par in the event of an acquisition of beneficial ownership of 30% or more of the outstanding voting stock of MGE Energy, (ii) MGE must maintain a ratio of its consolidated indebtedness to consolidated total capitalization not to exceed a maximum of 65%, and (iii) MGE cannot issue "Priority Debt" in an amount exceeding 20% of its consolidated assets. Priority Debt is defined as any indebtedness of MGE secured by liens other than specified liens permitted by the Note Purchase Agreement and certain unsecured indebtedness of certain subsidiaries. As of December 31, 2025, MGE was in compliance with the covenant requirements. (e) Issued by MGE Power West Campus. The Note Purchase Agreements require MGE Power West Campus to maintain a projected debt service coverage ratio of not less than 1.25 to 1.00, and debt to total capitalization ratio of not more than 0.65 to 1.00. The notes are secured by a collateral assignment of lease payments that MGE is making to MGE Power West Campus for use of the WCCF pursuant to a long-term lease. As of December 31, 2025, MGE Power West Campus was in compliance with the covenant requirements. (f) In October 2025, MGE entered into a private placement Note Purchase Agreement in which it committed to issue $25 million of new long-term debt (Series A), carrying an interest rate of 5.12% per annum over its 11-year life, and $25 million of new long-term debt (Series B), carrying an interest rate of 5.76% per annum over its 30-year life. Funding occurred on November 13, 2025. The proceeds of the senior notes will be used to assist with capital expenditures and other corporate obligations. The covenants of this debt are substantially consistent with the covenants applicable to MGE's existing unsecured senior notes. (g) Issued by MGE Power Elm Road. The Note Purchase Agreement requires MGE Power Elm Road to maintain a projected and actual debt service coverage ratio at the end of any calendar quarter of not less than 1.25 to 1.00 for the trailing 12-month period. The notes are secured by a collateral assignment of lease payments that MGE is making to MGE Power Elm Road for use of the Elm Road Units pursuant to long-term leases. As of December 31, 2025, MGE Power Elm Road was in compliance with the covenant requirements.
Schedule of Long-Term Debt Maturities | Below is MGE Energy's and MGE's aggregate maturities for all long-term debt for years following December 31, 2025.
(In thousands) |  | 2026 |  |  | 2027 |  |  | 2028 |  |  | 2029 |  |  | 2030 |  |  | Thereafter |
Long-term debt maturities |  | $ | 21,633 |  |  | $ | 54,888 |  |  | $ | 25,753 |  |  | $ | 55,926 |  |  | $ | 6,110 |  |  | $ | 653,805 |

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