XML 37 R16.htm IDEA: XBRL DOCUMENT
v3.25.4

Joint Plant Ownership | 12 Months Ended
--- | ---
Dec. 31, 2025
Regulated Operations [Abstract] |
Joint Plant Ownership | Joint Plant Ownership - MGE Energy and MGE. MGE has undivided ownership interests in jointly owned facilities. Generation and operating expenses are primarily divided between the joint owners under the same method as ownership. MGE provides its own financing, and the respective portion of facilities and costs are included in the corresponding operating expenses (fuel for electric generation, purchased power, other operations and maintenance, etc.) in the consolidated statements of income. The following tables show MGE's interest in utility plant in service, operating expense (net of deferred costs), and the related accumulated depreciation reserves and other information related to MGE's jointly owned facilities:
(In thousands, except for percentages and MW) |  | Columbia(a) |  | Elm Road(b) |  | West Campus(c) |  | West Riverside(d) |  | Forward Wind(e)
Ownership interest |  |  |  | 19 |  | % |  |  |  | 8.33 |  | % |  |  |  | 55 |  | % |  |  |  | 6.9 |  | % |  |  |  | 12.8 |  | %
Fuel source |  |  | Coal |  |  | Coal |  |  | Natural gas |  |  | Natural gas |  |  | Wind
Share of generation |  |  |  | 211 |  | MW |  |  |  | 106 |  | MW |  |  |  | 157 |  | MW |  |  |  | 50 |  | MW |  |  |  | 18 |  | MW
For the year ended December 31, |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating expense - 2025 |  | $ |  | 37,684 |  |  |  | $ |  | 23,809 |  |  |  |  | (f) |  |  |  | $ |  | 1,826 |  |  |  | $ |  | 596 |  |
Operating expense - 2024 |  |  |  | 29,815 |  |  |  |  |  | 21,511 |  |  |  |  | (f) |  |  |  |  |  | 5,954 |  |  |  |  |  | 755 |  |
Operating expense - 2023 |  |  |  | 30,103 |  |  |  |  |  | 21,072 |  |  |  |  | (f) |  |  |  |  |  | 3,214 |  |  |  |  |  | 677 |  |
As of December 31, 2025 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Utility plant |  | $ |  | 301,705 |  |  |  | $ |  | 209,502 |  |  |  | $ |  | 124,316 |  |  |  | $ |  | 56,394 |  |  |  | $ |  | 34,348 |  |
Accumulated depreciation |  |  |  | (202,111 | ) |  |  |  |  | (51,850 | ) |  |  |  |  | (45,346 | ) |  |  |  |  | (9,331 | ) |  |  |  |  | (19,123 | ) |
Construction work in progress |  |  |  | 4,665 |  |  |  |  |  | 485 |  |  |  |  |  | 4,174 |  |  |  |  |  | 342 |  |  |  |  |  | 3,954 |  |
As of December 31, 2024 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Utility plant |  | $ |  | 299,048 |  |  |  | $ |  | 207,070 |  |  |  | $ |  | 118,317 |  |  |  |  |  | 54,996 |  |  |  | $ |  | 34,363 |  |
Accumulated depreciation |  |  |  | (177,472 | ) |  |  |  |  | (47,494 | ) |  |  |  |  | (41,939 | ) |  |  |  |  | (7,421 | ) |  |  |  |  | (18,069 | ) |
Construction work in progress |  |  |  | 1,724 |  |  |  |  |  | 514 |  |  |  |  |  | 3,052 |  |  |  |  |  | 404 |  |  |  |  |  | — |  |
(a) As of December 31, 2024, coal operations were expected to conclude at Columbia Units 1 and 2 by the end of 2029, and thus at that time Columbia Units 1 and 2 met the criteria to be considered probable of abandonment. As a minority owner, MGE and the other Columbia co-owners currently plan to continue coal operations at least through 2029. Final timing and retirement dates continue to be evaluated, and depend upon operational regulatory considerations, capacity needs, and availability. As of December 31, 2025, early retirement of Columbia Unit 1 and 2 was no longer probable. See Footnote 4 for further information. (b) Two coal-fired generating units in Oak Creek, Wisconsin. In October 2025, MGE, along with the plant co-owners, filed a joint application with the PSCW to end the use of coal as a primary fuel at the Elm Road Units and transition the plant to natural gas. By the end of 2030, coal is expected to be used only as a backup fuel at the Elm Road Units. By the end of 2032, MGE expects that the Elm Road Units will be fully transitioned away from coal. (c) MGE Power West Campus and the UW jointly own the West Campus Cogeneration Facility (WCCF) located on the UW campus in Madison, Wisconsin. The UW owns a controlling interest in the chilled-water and steam plants, which are used to meet the needs for air-conditioning and steam-heat capacity for the UW campus. MGE Power West Campus owns a controlling interest in the electric generation plant, which is leased and operated by MGE. (d) In March 2023, MGE purchased an ownership interest in West Riverside, a natural gas-fired facility located in Beloit, WI, from WPL, operator and co-owner of the plant. West Riverside was placed in-service in 2020. In June 2024, MGE purchased an additional ownership interest in West Riverside, increasing its interest to 6.9%. (e) The Forward Wind Energy Center (Forward Wind) consists of 86 wind turbines located near Brownsville, Wisconsin. (f) Operating charges are allocated to the UW based on formulas contained in the operating agreement. Under the provisions of this arrangement, the UW is required to reimburse MGE for their allocated portion of fuel and operating expenses. For the years ended December 31, 2025, 2024, and 2023, the UW's allocated share of fuel and operating costs was $8.4 million, $7.0 million, and $6.7 million, respectively.
(In thousands, except for percentages and MW) |  | Two Creeks(g) |  | Badger Hollow I & II(h) |  | Red Barn(i) |  | Paris(j) |  | Darien(k)
Ownership interest |  |  |  | 33 |  | % |  |  |  | 33 |  | % |  |  |  | 10 |  | % |  |  |  | 10 |  | % |  |  |  | 10 |  | %
Fuel Source |  |  | Solar |  |  | Solar |  |  | Wind |  |  | Solar/Battery |  |  | Solar
Share of generation |  |  |  | 50 |  | MW |  |  |  | 100 |  | MW |  |  |  | 9.16 |  | MW |  |  | 20/11 |  | MW |  |  |  | 25 |  | MW
For the year ended December 31, |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating expense - 2025 |  | $ |  | 1,137 |  |  |  | $ |  | 1,804 |  |  |  | $ |  | 209 |  |  |  | $ |  | 441 |  |  |  | $ |  | 295 |  |
Operating expense - 2024 |  |  |  | 961 |  |  |  |  |  | 1,494 |  |  |  |  |  | 213 |  |  |  |  |  | 23 |  |  |  |  | N/A |  |
Operating expense - 2023 |  |  |  | 1,087 |  |  |  |  |  | 751 |  |  |  |  |  | 143 |  |  |  |  | N/A |  |  |  |  | N/A |  |
As of December 31, 2025 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Utility plant |  | $ |  | 68,003 |  |  |  | $ |  | 161,432 |  |  |  | $ |  | 16,750 |  |  |  | $ |  | 27,549 |  |  |  | $ |  | 1,998 |  |
Accumulated depreciation |  |  |  | (12,357 | ) |  |  |  |  | (16,276 | ) |  |  |  |  | (1,391 | ) |  |  |  |  | (586 | ) |  |  |  |  | (44 | ) |
Construction work in progress |  |  |  | 37 |  |  |  |  |  | — |  |  |  |  |  | 22 |  |  |  |  |  | — |  |  |  |  |  | — |  |
As of December 31, 2024 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Utility plant |  | $ |  | 67,999 |  |  |  | $ |  | 160,954 |  |  |  |  |  | 16,484 |  |  |  |  |  | 40,565 |  |  |  |  | N/A |  |
Accumulated depreciation |  |  |  | (9,951 | ) |  |  |  |  | (10,639 | ) |  |  |  |  | (872 | ) |  |  |  |  | — |  |  |  |  | N/A |  |
Construction work in progress |  |  |  | — |  |  |  |  |  | 368 |  |  |  |  |  | — |  |  |  |  |  | — |  |  |  |  | N/A |  |
(g) The Two Creeks solar generation array is located in the Town of Two Creeks and the City of Two Rivers in Manitowoc and Kewaunee Counties, Wisconsin. Date of commercial operation of the solar array was November 2020. (h) The Badger Hollow I and II solar farm is located in southwestern Wisconsin in Iowa County, near the villages of Montfort and Cobb. Date of commercial operation of Badger Hollow I was November 2021 and December 2023 for Badger Hollow II. (i) The Red Barn Wind Farm is located in the Towns of Wingville and Clifton in Grant County, Wisconsin. MGE purchased its share of Red Barn in 2023. (j) The Paris Solar-Battery Park is located in the Town of Paris in Kenosha County, Wisconsin. Date of commercial operation of the solar array was December 2024. Date of commercial operation of battery was June 2025. (k) The Darien Solar Energy Center is located in Walworth and Rock Counties in southern Wisconsin. Date of commercial operation of the solar array was March 2025. MGE currently has ongoing jointly-owned generation construction projects, as shown in the following table. Incurred costs are reflected in "Property, plant, and equipment, net" or "Construction work in progress" on the consolidated balance sheets.
Project |  | Ownership Interest |  | Source |  | Share of Generation |  | Share of Estimated Costs(a) |  | Costs incurred as of December 31, 2025(a) |  | Estimated Date of Commercial Operation
Darien(b) |  | 10% |  | Battery |  | 7.5 MW |  | $18 million(j) |  | $7.4 million |  | 2026
Koshkonong(c) |  | 10% |  | Solar/Battery |  | 30 MW/16.5 MW |  | $93 million(j) |  | $64.7 million |  | 2026 Solar 2027 Battery
High Noon(d) |  | 10% |  | Solar/Battery |  | 30 MW/16.5 MW |  | $99 million |  | $59.5 million |  | 2027
Columbia Energy Dome(e) |  | 19% |  | Storage |  | 3 MW |  | $22 million(j) |  | $2.7 million |  | 2027
Badger Hollow(f) |  | 10% |  | Wind |  | 11.2 MW |  | $36 million |  | $5.6 million |  | 2027
Whitetail(g) |  | 10% |  | Wind |  | 6.7 MW |  | $23 million |  | $1.2 million |  | 2027
Ursa(h) |  | 10% |  | Solar |  | 20 MW |  | $46 million |  | $6.4 million |  | 2028
Saratoga(i) |  | 10% |  | Solar/Battery |  | 15 MW/5 MW |  | $46 million |  | $10.2 million |  | 2028
(a) Excluding AFUDC. (b) Darien Solar Energy Center is located in Walworth and Rock Counties in southern Wisconsin. (c) Koshkonong Solar Energy Center is located in the Towns of Christiana and Deerfield in Dane County, Wisconsin. (d) High Noon Solar Project is located in Columbia County, Wisconsin. (e) Columbia Energy Dome is located in Columbia County, Wisconsin. (f) Badger Hollow Wind is located in Iowa and Grant Counties, Wisconsin. (g) Whitetail Wind is located in Grant County, Wisconsin. (h) Ursa Solar Park is located in Columbia County, Wisconsin. (i) Saratoga Solar Energy Center is located in Wood County, Wisconsin. (j) Estimated costs are expected to exceed PSCW previously approved Certificate of Authority (CA) levels. Notifications are provided to the PSCW when costs increase above CA levels. MGE has and will continue to request recovery of the updates in its rate case proceedings.

X
- Definition Describes significant information about our ongoing solar generation projects: Two Creeks and Bager Hollow I and II. + References No definition available. + Details
Name: | mgee_JointlyOwnedUtilityPlantInterestsTextBlock
Namespace Prefix: | mgee_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_RegulatedOperationsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration