Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2025

Asset Retirement Obligation Disclosure [Abstract]

Change in Asset Retirement Obligations

The following table summarizes the change in AROs. Amounts include conditional AROs.

(In thousands)	2025			2024
Balance as of January 1,	$	69,132		$	54,430
Liabilities incurred(a)		3,010			25,756
Accretion expense		3,435			2,671
Liabilities settled(b)		(808	)		(7,548	)
Revisions in estimated cash flows(c)		1,520			(6,177	)
Balance as of December 31,	$	76,289		$	69,132

(a)In June 2024, MGE recorded an asset retirement obligation for its estimated share of the legal liability associated with the effect of the CCR Legacy Rule for remediation and groundwater compliance monitoring at Columbia. See Footnote 16 for further information on the CCR Legacy Rule.

(b)In 2024, MGE settled $6.8 million of liabilities related to the Columbia Ash Pond.

(c)In December 2024, revisions were made related to the Columbia CCR asset retirement obligation estimates based on additional analysis completed on the impacted areas.