XML 23 R11.htm IDEA: XBRL DOCUMENT
v3.26.1

Investment in ATC and ATC Holdco | 6 Months Ended
--- | ---
Jun. 30, 2026
Equity Method Investments and Joint Ventures [Abstract] |
Investment in ATC and ATC Holdco | Investme nt in ATC and ATC Holdco - MGE Energy and MGE. ATC owns and operates electric transmission facilities primarily in Wisconsin. MGE received an interest in ATC when it, like other Wisconsin electric utilities, contributed its electric transmission facilities to ATC, as required by Wisconsin law. That interest is presently held by MGE Transco, a subsidiary of MGE Energy. ATC Holdco was formed by several members of ATC, including MGE Energy, to pursue electric transmission development and investments outside of Wisconsin. The ownership interest in ATC Holdco is held by MGEE Transco, a subsidiary of MGE Energy. MGE Transco and MGEE Transco have accounted for their investments in ATC and ATC Holdco, respectively, under the equity method of accounting. Equity earnings from investments are recorded as "Other income" on the consolidated statements of income of MGE Energy. MGE Transco recorded the following amounts related to its investment in ATC:
|  | Three Months Ended |  |  | Six Months Ended |
|  | June 30, |  |  | June 30, |
(In thousands) |  | 2026 |  |  | 2025 |  |  | 2026 |  |  | 2025 |
Equity earnings from investment in ATC |  | $ | 3,776 |  |  | $ | 3,066 |  |  | $ | 7,298 |  |  | $ | 6,056 |
Dividends received from ATC |  |  | 2,788 |  |  |  | 2,345 |  |  |  | 5,450 |  |  |  | 5,632 |
Capital contributions to ATC |  |  | 2,156 |  |  |  | 2,679 |  |  |  | 6,616 |  |  |  | 5,171 |
In July 2026, MGE Transco made a $3.6 million capital contribution to ATC. ATC's summarized financial data is as follows:
|  | Three Months Ended |  |  | Six Months Ended |
|  | June 30, |  |  | June 30, |
(In thousands) |  | 2026 |  |  | 2025 |  |  | 2026 |  |  | 2025 |
Operating revenues |  | $ | 274,048 |  |  | $ | 241,227 |  |  | $ | 539,307 |  |  | $ | 476,156 |
Operating expenses |  |  | (129,636 | ) |  |  | (117,564 | ) |  |  | (257,041 | ) |  |  | (234,309 | )
Other income, net |  |  | 1,228 |  |  |  | 550 |  |  |  | 1,928 |  |  |  | 633 |
Interest expense, net |  |  | (45,925 | ) |  |  | (43,254 | ) |  |  | (90,401 | ) |  |  | (82,447 | )
Earnings before members' income taxes |  | $ | 99,715 |  |  | $ | 80,959 |  |  | $ | 193,793 |  |  | $ | 160,033 |
MGE receives transmission and other related services from ATC. During the three and six months ended June 30, 2026, MGE recorded $11.2 million and $22.4 million, respectively, for transmission service compared to $10.2 million and $20.4 million for the comparable periods in 2025. MGE also provides a variety of operational, maintenance, and project management work for ATC, which is reimbursed by ATC. As of June 30, 2026, and December 31, 2025, MGE had a receivable due from ATC of $3.7 million and $2.5 million, respectively. The receivable is primarily related to transmission interconnection activities at the renewable generation sites. MGE will be reimbursed for these costs after the new generation assets are placed into service.

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

X
- Definition The entire disclosure for equity method investments and joint ventures. Equity method investments are investments that give the investor the ability to exercise significant influence over the operating and financial policies of an investee. Joint ventures are entities owned and operated by a small group of businesses as a separate and specific business or project for the mutual benefit of the members of the group. + References Reference 1: http://www.xbrl.org/2003/role/recommendedDisclosureRef -Topic 740 -SubTopic 323 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478156/740-323-50-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 323 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481687/323-10-50-3 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 323 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481687/323-10-50-3 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Topic 323 -Publisher FASB -URI https://asc.fasb.org/323/tableOfContent + Details
Name: | us-gaap_EquityMethodInvestmentsDisclosureTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration