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|  | UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 |  |
| FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 |
|  | May 8, 2026 Date of report (date of earliest event reported) |  |
Commission File No. |  | Name of Registrant, State of Incorporation, Address of Principal Executive Offices, and Telephone No. |  | IRS Employer Identification No.
000-49965 |  | MGE Energy, Inc. (a Wisconsin Corporation) 133 South Blair Street Madison, Wisconsin 53788 (608) 252-7000 | mgeenergy.com |  | 39-2040501
000-1125 |  | Madison Gas and Electric Company (a Wisconsin Corporation) 133 South Blair Street Madison, Wisconsin 53788 (608) 252-7000 | mge.com |  | 39-0444025

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class |  | Trading symbol(s) |  | Name of each exchange on which registered
Common Stock, $1 Par Value Per Share |  | MGEE |  | The NASDAQ Stock Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

MGE Energy, Inc. ☐ Madison Gas and Electric Company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.

MGE Energy, Inc. ☐ Madison Gas and Electric Company ☐

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Item 7.01. Regulation FD Disclosure.

On May 8, 2026, MGE Energy, Inc. posted a financial presentation on its Investor Relations website. A copy of the presentation is attached as Exhibit 99.1. Representatives of MGE Energy, Inc. will be participating in upcoming meetings with investors at the 2026 AGA Financial Forum in Scottsdale, Arizona, May 17-18, 2026. This Form 8-K and the attached exhibits are furnished to, but not filed with, the Securities and Exchange Commission.

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits.

Exhibit No. |  | Description
99.1 |  | Presentation Slides.
104 |  | Cover Page Interactive Data File (the cover page XBRL tags are embedded in the Inline XBRL document).

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrants have duly caused this report to be signed on their behalf by the undersigned hereunto duly authorized.

| MGE Energy, Inc. Madison Gas and Electric Company
| (Registrants)
Date: May 8, 2026 | /s/ Jenny L. Lagerwall
| Jenny L. Lagerwall Assistant Vice President - Accounting and Controller (Chief Accounting Officer)

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