Additional Proxy Soliciting Materials (Form DEFA14A)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

Filed by the Registrant ☒       Filed by a Party other than the Registrant ☐

Check the appropriate box:

POWER SOLUTIONS INTERNATIONAL, INC.

Payment of Filing Fee (Check the appropriate box):

Your Vote Counts! POWER SOLUTIONS INTERNATIONAL, INC. 201 MITTEL DRIVE WOOD DALE, IL 60191 ATTN: KEN JENKE T00922-P54276 You invested in POWER SOLUTIONS INTERNATIONAL, INC. and it's time to vote! You have the right to vote on proposals being presented at the Annual Meeting. This is an important notice regarding the availability of proxy materials for the stockholder meeting to be held on July 23, 2026. Get informed before you vote View the Notice of Annual Meeting, Proxy Statement and Annual Report on Form 10-K online OR you can receive a free paper or email copy of the material(s) by requesting prior to July 9, 2026. If you would like to request a copy of the material(s) for this and/or future stockholder meetings, you may (1) visit www.ProxyVote.com, (2) call 1-800-579-1639 or (3) send an email to [email protected]. If sending an email, please include your control number (indicated below) in the subject line. Unless requested, you will not otherwise receive a paper or email copy. Smartphone users Point your camera here and vote without entering a control number Virtually at: Vote Virtually at the Meeting* July 23, 2026 8:00 a.m., Central Time www.virtualshareholdermeeting.com/PSIX2026 *Please check the meeting materials for any special requirements for meeting attendance.

Vote at www.ProxyVote.com THIS IS NOT A VOTABLE BALLOT This is an overview of the proposals being presented at the upcoming stockholder meeting. Please follow the instructions on the reverse side to vote these important matters. Voting Items Board Recommends 1.Election of Directors Nominees: 1a. Jiwen Zhang For 1b. Xuesen Yang For 1c. Frank P. Simpkins For 1d. Courtney C. Shea For 1e. Hong He For 1f. Zhao Jin For 1g. Fuzhang Yu For 2.Ratification of the appointment of BDO USA, P.C. as the independent registered public accounting firm for the fiscal year ending December 31, 2026. For 3.To approve, by non-binding advisory vote, the compensation of the Company's named executive officers. For 4.To recommend, in a stockholder non-binding advisory vote, the frequency of votes of the compensation of the Company's named executive officers. 1 Year NOTE: Such other business as may properly come before the meeting or any adjournment thereof. Prefer to receive an email instead? While voting on www.ProxyVote.com, be sure to click "Delivery Settings". T00923-P54276