Otter Tail Corp

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

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Exchange Act of 1934 (Amendment No. )

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OTTER TAIL CORPORATION

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OTTER TAIL CORPORATION

ANNUAL MEETING OF SHAREHOLDERS

Monday, April 14, 2025

10:00 A.M. (CDT)

Virtual Meeting Link: www.virtualshareholdermeeting.com/OTTR2025.

In order to be admitted to the Annual Meeting, you will need to enter the 16-Digit Control Number found on your proxy card, voting instruction form, or Notice you previously received. You may vote during the Annual Meeting by following the instructions that will be available on the virtual meeting website.

Contact Shareholder

Services for Information

March 3, 2025

Dear Shareholders:

We invite you to join us at our virtual 2025 Annual Meeting of Shareholders on Monday, April 14, 2025 at 10:00 A.M. (CDT). An audio archive of the Annual Meeting, including the question and answer session, will be posted on Otter Tail Corporation’s website atwww.ottertail.com within a few days after the meeting’s adjournment.

Otter Tail Corporation produced record earnings in 2024, generating diluted earnings per share of $7.17. We produced a return on equity of 19 percent on an equity layer of 62 percent. In addition, 2024 marked the completion of the 86th consecutive year of paying dividends to our shareholders. Finally, in February 2025, we increased our dividend by 12 percent producing an annual indicated dividend of $2.10.

In 2024, our regulated electric utility, Otter Tail Power Company, continued to execute on its regulatory priorities. It received approval from the Minnesota Public Utilities Commission on its Integrated Resource Plan and approval from the North Dakota Public Service Commission for its general rate case. Otter Tail Power also continued to deliver on its significant rate base growth plan, investing to provide safe, reliable, efficient and increasingly clean electric service to our customers while maintaining some of the lowest electric service rates in the nation.

Our manufacturing platform faced changing market conditions throughout 2024. Our manufacturing businesses continue to navigate softened end market demand but remain well positioned to respond once demand improves. Our plastic pipe businesses produced another year of strong financial results, benefiting from customer sales volume growth and improved end market demand. We completed the first phase of Vinyltech Corporation’s expansion project, adding large diameter PVC pipe production capability, and look forward to completing our expansion project at BTD Georgia in early 2025, positioning us to better serve our customers in the southeast.

Our diversified business model continues to serve us and our stakeholders well, as our manufacturing platform generates accretive earnings, enhanced returns and positive free cash flow to fund our electric utility rate base growth plan without any equity needs. We look forward to sharing more about our 2024 operational and financial results, as well as our long-term strategy to continue to produce value for our employees, customers and shareholders during the 2025 Annual Meeting.

Your vote is important. Information concerning the matters to be considered and voted upon at the 2025 Annual Meeting along with instructions on how to vote your shares is set out in the attached Notice of 2025 Annual Meeting and Proxy Statement. Please be sure to retain your Notice or proxy card (if you received a printed copy of the proxy materials), which has your 16-Digit Control Number required to be admitted into the 2025 Annual Meeting.

Thank you for your confidence and investment in Otter Tail Corporation.

Notice of Annual Meeting

Table of Contents

Forward-Looking Statements

The statements contained in this Proxy Statement about our future performance and operations, including, without limitation, financial and operational results, use of renewable resources and carbon emissions reductions, strategies, visions, prospects, plans, targets, goals, objectives, opportunities, consequences and all other statements that are not purely historical, are forward-looking statements for purposes of the safe harbor provisions under The Private Securities Litigation Reform Act of 1995. Although we believe that our expectations are based on information currently available and on reasonable assumptions, we can give no assurance they will be achieved. There are a number of risks and uncertainties that could cause actual results to differ materially from any forward-looking statements made herein. A discussion of some of these risks and uncertainties is contained in our Annual Report on Form 10-K and subsequent reports filed with the Securities and Exchange Commission (“SEC”), and available on our website: www.ottertail.com. In addition, any forward-looking statements included herein represent our estimates only as of the date hereof and should not be relied upon as representing our estimates as of any subsequent date. While we may elect to update forward-looking statements from time to time, we specifically disclaim any obligation to do so, even if our internal estimates change, unless otherwise required by applicable securities laws.