MGE ENERGY INC

UNITED STATESSECURITIES AND EXCHANGE COMMISSIONWashington, D.C. 20549

SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of theSecurities Exchange Act of 1934

Filed by registrant: ☒ Filed by a Party other than the Registrant: ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☒ Definitive Proxy Statement ☐ Definitive Additional Materials ☐ Soliciting Material under §240.14a-12 MGE Energy, Inc.(Name of Registrant as Specified In Its Charter) (Name of Person(s) Filing Proxy Statement, if Other Than the Registrant) Payment of Filing Fee (Check all boxes that apply): ☒ No Fee Required ☐ Fee paid previously with preliminary materials ☐ Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a6(i)(1) and 0-11

About MGE Energy MGE Energy, Inc. (MGE Energy or the Company), is an investor-owned public utility holding company headquartered in the state capital of Madison, Wis. MGE Energy is the parent company of Madison Gas and Electric Company (MGE), your community energy company. With roots in the community dating back more than 150 years, the utility provides affordable natural gas and electric service in south-central and western Wisconsin.

Our Mission We are committed to industry leadership, to customer engagement in many different ways and to safe, reliable, affordable and sustainable energy. Your community energy company is growing its use of cost-effective carbon-free energy resources and partnering with customers to advance innovative solutions that meet their needs, manage energy affordability and achieve shared energy goals.

Our Decarbonization Strategies Your community energy company is pursuing globally recognized strategies to achieve our goal ofnet-zero carbon electricity by 2050. To achieve our sustainability goals, we are:▪Decarbonizing our energy supply cost-effectively.▪Partnering with our customers in new, innovative ways to help manage their energy use.▪Electrifying transportation, the largest source of direct greenhouse gas emissions, and other end uses.▪Building a more dynamic, integrated grid to enable new technologies.▪Balancing this transition to a net-zero carbon future to ensure all our customers benefit.

From Our Chairman, President and CEO

Dear Fellow Shareholders: In 2025, MGE Energy marked 50 consecutive years of dividend increases, joining only a select number of companies to achieve that milestone. Our record is indicative of our ongoing commitment to consistent growth and to responsible financial stewardship of your investment. Thank you for the trust and confidence you have in our Company. I look forward to the opportunity to discuss our performance during our Annual Meeting of Shareholders on Tuesday, May 19, 2026. Please join us online beginning at 11 a.m., Central Time. With nearly $2 billion in projected capital investment within the next five years, we remain focused on providing safe, reliable and affordable energy for the customers and communities we are privileged to serve. Our planned investments in wind, solar, battery storage and natural gas generation will help to ensure ongoing top-ranked electric reliability as we continue to transition our energy supply responsibly. In 2025, we continued to grow our use of renewables and battery storage serving our grid:

Jeff Keebler

Chairman, President and CEO

•

Paris Battery Energy Storage: Wisconsin's first large-scale battery storage project came online in June 2025. MGE owns 11 megawatts (MW) of battery storage and 20 MW of solar at the 310-MW Paris Solar-Battery Park in Kenosha County.

•

Darien Solar: MGE owns 10% of the 250-MW solar project in southern Wisconsin, which also features 75 MW of battery energy storage expected online in 2026.

•

Strix Solar: One-third of MGE's 6-MW Strix Solar project outside of Madison, Wisconsin, serves the Company’s new community solar program. The remaining capacity serves all MGE electric customers with cost-effective local solar energy.

The Company’s current capital plan supports the additional development of nearly 400 MW of renewables and energy storage in the next five years.

In March 2026, MGE applied for State regulatory approval to purchase a share of the existing natural gas-fired RockGen Energy Center. Cost-effective natural gas supports the Company’s renewables growth by helping to ensure reliability during extreme conditions, such as the severe cold weather this past winter. If approved, we expect to close on the purchase in 2027.

Safe, reliable, affordable energy is our fundamental obligation to our customers. It helps our communities continue to grow and to thrive as new large-load customers seek opportunities in Wisconsin. Your community energy company is working to support the continued health and vitality of our communities through our ongoing economic development efforts and the creation of new rate structures to serve very large customers.

We also continue working in multiple ways to maintain energy affordability, including through innovative partnerships with customers and other stakeholders. MGE’s affordability as a percentage of customer wallet has improved 20% since 2014. Maintaining energy affordability is a top priority as we work to meet our communities’ sustainability goals and reliability needs and advance new energy solutions for the future.

Thank you for your valued partnership and investment in MGE Energy. Please review this Proxy Statement and cast your vote promptly.

Sincerely,

Jeff M. Keebler

Chairman, President and CEO

April 2, 2026

From Our Lead Independent Director

Dear Fellow Shareholders: As Lead Independent Director, I am pleased to provide a brief overview of the board’s ongoing work to provide strong governance. We continue our oversight of MGE Energy’s long-term strategy. With ten meetings of the full board annually, directors are actively engaged, receiving regular briefings from subject matter experts on matters critical to our business and evolving industry.Board Oversight and Strategic DirectionThe board remains focused on overseeing the Company’s continued delivery of safe, reliable, affordable, and increasingly sustainable energy, with more than 40 clean energy and battery storage projects announced in the last 10 years. We engage management regularly on the Company’s substantial and ongoing investment in generation and infrastructure to enhance grid reliability. These efforts support long-term system resilience, customer and community expectations, and economic development throughout the service territory.

Jim Possin

Lead Independent Director

Governance, Independence, and Board EffectivenessEight out of our 10 directors are independent, ensuring robust independent oversight. Independent directors meet regularly without management to review strategy, risk, and performance. Our oversight encompasses strategic planning, major capital projects, enterprise‑wide risk assessments, market and regulatory trends, and key operational matters, including cybersecurity and new and emerging technologies.Our experienced and highly engaged board is well positioned to support the Company's long-term needs through the range of skills our directors bring to their service. Further, our annual director peer- and self-evaluation process strengthens our preparedness to navigate evolving regulatory, operational and market dynamics.Reliability and Responsible StewardshipMGE continues to be recognized for delivering top-ranked electric reliability, which reflects both disciplined operational practices and strategic investments in our electric generation and distribution system. Our board is deeply committed to ensuring the Company delivers on its responsibilities while transitioning our energy supply and electric grid for the future. On behalf of the board, thank you for your continued support of MGE Energy. We are committed to representing your interests and creating long-term value for our investors and the communities that depend on the Company for safe, reliable energy. Please review this Proxy Statement and exercise your right to vote your shares. Our shareholders’ perspectives help to inform the future of your Company. On behalf of the board, we look forward to your participation at the upcoming Annual Meeting.

Sincerely,

James L. Possin

Lead Independent Director

April 2, 2026

Notice of 2026 Annual Meeting of Shareholders

Regardless of whether you plan to attend the MGE Energy, Inc., 2026 Annual Meeting of Shareholders (the Annual Meeting), please take a moment to vote your proxy.

The Annual Meeting will be held virtually, using the same format as last year's meeting. As always, we encourage you to vote your shares prior to the meeting date.

By Order of the Board of Directors,

Cari Anne Renlund

Vice President General Counsel and Secretary

This notice of Annual Meeting, Proxy Statement and accompanying proxy card are first being mailed on or about April 2, 2026, to shareholders of record at the close of business on March 23, 2026, the record date for this meeting.

Important Notice Regarding the Availability of Proxy Materials for the Annual Meeting to be Held on May 19, 2026:

This Proxy Statement and our 2025 Annual Report to Shareholders are available atwww.mgeenergy.com/proxy.

Table of Contents