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Exhibit 5.1

May 3, 2023

Advanced Energy Industries, Inc.

1595 Wynkoop Street, Suite 800

Denver, Colorado 80202

Ladies and Gentlemen:

We have acted as counsel for Advanced Energy Industries, Inc., a Delaware corporation (the “Company”), in conjunction with the preparation of a Registration Statement on Form S-8 (the “Registration Statement”) to be filed by the Company with the Securities and Exchange Commission under the Securities Act of 1933, as amended (the “Securities Act”), registering 2,400,000 shares (the “Registered Shares”) of the Company’s common stock, par value $0.001 per share (“Common Stock”), that may be issued pursuant to the Advanced Energy Industries, Inc. 2023 Omnibus Incentive Plan (the “2023 Plan”).

In connection with our representation, we have examined:  (a) the 2023 Plan and related documents; (b) the Registration Statement, including the exhibits (including those incorporated by reference) constituting a part of the Registration Statement; (c) the Certificate of Incorporation of the Company and the By-Laws of the Company, as amended to date; (d) the resolutions of the Company’s Board of Directors relating to the 2023 Plan and the issuance of Common Stock thereunder; and (e) such other corporate proceedings, documents and records as we have deemed necessary or appropriate to enable us to render this opinion.

In our examination of the above-referenced documents, we have assumed the genuineness of all signatures, the legal capacity and competency of all natural persons, the authenticity of all documents, certificates and instruments submitted to us as originals and the conformity with the originals of all documents submitted to us as copies.  We have also assumed the accuracy of all other information provided to us by the Company during the course of our investigations, on which we have relied in issuing the opinion expressed below.

For the purpose of the opinion rendered below, we have assumed that in connection with the issuance of the Registered Shares under the 2023 Plan, the Company will receive consideration in an amount not less than the aggregate par value of the Registered Shares covered by each such issuance.

It is understood that this opinion is to be used only in connection with the offer and sale of the Registered Shares while the Registration Statement is effective.

We express no opinion herein as to the laws of any state or jurisdiction other than the General Corporation Law of the State of Delaware and the federal laws of the United States of America.  This opinion is being furnished in connection with the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act, and no opinion is expressed herein as to any matter pertaining to the contents of the Registration Statement or the prospectus that forms a part thereof, other than as expressly stated herein with respect to the issuance of the Registered Shares.

AUSTIN Boston CHICAGO dallas DENVER DETROIT houston JACKSONVILLE LOS ANGELES MADISON MEXICO CITY MIAMI MILWAUKEE NEW YORK ORLANDO SACRAMENTO Salt lake city SAN DIEGO SAN FRANCISCO SILICON VALLEY TALLAHASSEE TAMPA WASHINGTON, D.C. BRUSSELS TOKYO

May 3, 2023

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Based upon the foregoing, we are of the opinion that each of the Registered Shares, if and when issued by the Company pursuant to the terms and conditions of the 2023 Plan and as contemplated by the Registration Statement, will be validly issued, fully paid and nonassessable.  

We consent to the use of this opinion as an exhibit to the Registration Statement.  In giving our consent, we do not admit that we are “experts” within the meaning of Section 11 of the Securities Act or within the category of persons whose consent is required by Section 7 of the Securities Act.

Very truly yours,

/s/ Foley & Lardner LLP

Foley & Lardner LLP