Joint Plant (Tables)

6 Months Ended

Jun. 30, 2025

Public Utilities, Property, Plant and Equipment [Abstract]

Schedule of Jointly Owned Utility Plants

MGE has ownership interests in generation projects with other co-owners, some of which are under construction, 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 June 30, 2025(a)	Date of Commercial Operation
Paris(b)	10%	Battery	11 MW	$25 million(g)	$23.4 million	June 2025 Battery
Darien(c)	10%	Solar/Battery	25 MW/7.5 MW	$63 million(g)	$46.3 million	March 2025 Solar 2026 Battery(h)
Koshkonong(d)	10%	Solar/Battery	30 MW/16.5 MW	$104 million(g)	$24.8 million	2026 Solar(h) 2027 Battery(h)
High Noon(e)	10%	Solar/Battery	30 MW/16.5 MW	$99 million	$17.8 million	2027(h)
Columbia Energy Dome(f)	19%	Storage	3 MW	$17 million	$0.7 million	2027(h)

(a)Excluding AFUDC.

(b)Paris Solar-Battery Park is located in the Town of Paris in Kenosha County, Wisconsin.

(c)Darien Solar Energy Center is located in Walworth and Rock Counties in southern Wisconsin.

(d)Koshkonong Solar Energy Center is located in the Towns of Christiana and Deerfield in Dane County, Wisconsin.

(e)High Noon Solar Project is located in Columbia County, Wisconsin.

(f)Columbia Energy Dome is located in Columbia County, Wisconsin.

(g)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.

(h)Estimated date of commercial operation.