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

(Amendment No.    )

Filed by the Registrant  þ                             Filed by a Party other than the Registrant  ¨

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¨ Preliminary Proxy Statement

¨ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

¨ Definitive Proxy Statement

þ Definitive Additional Materials

¨ Soliciting Material Pursuant to §240.14a-12

Powell Industries, Inc.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

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þ No fee required.

¨ Fee computed on table below per Exchange Act Rules 14a-6(i)(1) and 0-11.

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¨ Fee paid previously with preliminary materials.

¨ Check box if any part of the fee is offset as provided by Exchange Act Rule 0-11(a)(2) and identify the filing for which the offsetting fee was paid previously. Identify the previous filing by registration statement number, or the Form or Schedule and the date of its filing.

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Signature of Stockholder Date: Signature of Stockholder Date: Note: Please sign exactly as your name or names appear on this Proxy. When shares are held jointly, each holder should sign. When signing as executor, administrator, attorney, trustee or guardian, please give full title as such. If the signer is a corporation, please sign full corporate name by duly authorized officer, giving full title as such. If signer is a partnership, please sign in partnership name by authorized person. To change the address on your account, please check the box at right and indicate your new address in the address space above. Please note that changes to the registered name(s) on the account may not be submitted via this method. 1. Election of the nominees listed below (except as indicated below) to the Board of Directors, class of 2017. O EUGENE L. BUTLER O CHRISTOPHER E. CRAGG O BONNIE V. HANCOCK 2. To approve the Company’s 2014 Equity Incentive Plan. 3. To approve the Company’s 2014 Non-Employee Director Equity Incentive Plan. 4. To approve, on an advisory basis, the compensation of executives, as disclosed pursuant to the compensation disclosure rules of the Securities and Exchange Commission, including the compensation discussion and analysis, the compensation tables and any related material disclosed in this proxy statement (“say-on-pay”). 5. In their discretion with respect to (1) any other matters as may properly come before the meeting and any adjournment thereof, (2) approval of the minutes of the prior meeting, if such approval does not amount to ratification of the action taken at that meeting, (3) the election of any other person as a director if a nominee named above is unable to serve or for good cause will not serve, and (4) matters incident to the conduct of the meeting. If properly executed, this voting instruction will be voted as directed herein. IF NO DIRECTION IS INDICATED WITH RESPECT TO THE ABOVE PROPOSALS, SHARES ALLOCATED WILL BE VOTED “FOR” THE BOARD OF DIRECTORS’ NOMINEES. FOR ALL NOMINEES WITHHOLD AUTHORITY FOR ALL NOMINEES FOR ALL EXCEPT (See instructions below) INSTRUCTIONS:To withhold authority to vote for any individual nominee(s), mark “FOR ALL EXCEPT” and fill in the circle next to each nominee you wish to withhold, as shown here: JOHN SMITH 1234 MAIN STREET APT. 203 NEW YORK, NY 10038 NOMINEES: ANNUAL MEETING OF STOCKHOLDERS OF POWELL INDUSTRIES, INC. February 26, 2014 INTERNET - Access “www.voteproxy.com” and follow the on-screen instructions or scan the QR code with your smartphone. Have your proxy card available when you access the web page. Vote online until 11:59 PM EST the day before the meeting. MAIL - Sign, date and mail your proxy card in the envelope provided as soon as possible. IN PERSON - You may vote your shares in person by attending the Annual Meeting. GO GREEN - e-Consent makes it easy to go paperless. With e-Consent, you can quickly access your proxy material, statements and other eligible documents online, while reducing costs, clutter and paper waste. Enroll today via www.amstock.com to enjoy online access. PROXY VOTING INSTRUCTIONS Please detach along perforated line and mail in the envelope provided IF you are not voting via the Internet. THE BOARD OF DIRECTORS RECOMMENDS A VOTE “FOR” THE ELECTION OF ALL NOMINEES, “FOR” THE APPROVAL OF THE COMPANY’S 2014 EQUITY INCENTIVE PLAN, “FOR” THE APPROVAL OF THE COMPANY’S 2014 NON-EMPLOYEE DIRECTOR EQUITY INCENTIVE PLAN AND “FOR” THE ADVISORY APPROVAL OF THE COMPANY’S EXECUTIVE COMPENSATION. PLEASE SIGN, DATE AND RETURN PROMPTLY IN THE ENCLOSED ENVELOPE. PLEASE MARK YOUR VOTE IN BLUE OR BLACK INK AS SHOWN HERE x --------------- ---------------- 20333300000000000000 0 022614 COMPANY NUMBER ACCOUNT NUMBER NOTICE OF INTERNET AVAILABILITY OF PROXY MATERIAL: The Notice of Meeting, proxy statement and proxy card are available at http://investor.shareholder.com/powell/annual-proxy.cfm FOR AGAINST ABSTAIN