Long-Term Debt (Details) (USD $)

MGE's utility plant is subject to the lien of its Indenture of Mortgage and Deed of Trust, under which its first mortgage bonds are issued. The Mortgage Indenture provides that dividends or any other distribution or purchase of 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 31,2014, approximately $334.8 million was available for the payment of dividends under this covenant.

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 first mortgage bonds.

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.

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, 2014, MGE is in compliance with the covenant requirements.

Issued by MGE Power West Campus. The Note Purchase Agreements require it 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 its ownership interest in the West Campus Cogeneration Facility pursuant to a long-term lease.As of December 31, 2014, MGE Power West Campus is in compliance with the covenant requirements.

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 its ownership interest in the Elm Road Units pursuant to long-term leases.As of December 31, 2014, MGE Power Elm Road is in compliance with the covenant requirements.

Includes $48.2 million for MGE Power West Campusand $68.0 million for MGE Power Elm Road, all of which are consolidated with MGE's debt (see Footnote 2 for further information).