STEM, INC.

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. )

Stem, Inc.

(Name of Registrant as Specified in Its Charter)

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

1400 Post Oak Boulevard, Suite 560, Houston, Texas 77056

NOTICE OF 2026 ANNUAL MEETING OF STOCKHOLDERS

TO BE HELD ON JUNE 3, 2026

To our Stockholders:

Stem, Inc. (the “Company”) will hold its 2026 Annual Meeting of Stockholders (the “Annual Meeting”) on Wednesday, June 3, 2026, beginning at 10:00 a.m. Central Time. The Annual Meeting will be a virtual meeting conducted exclusively online via live audio webcast atwww.virtualshareholdermeeting.com/STEM2026. The Annual Meeting will be held for the following purposes, as more fully described in the accompanying proxy statement (the “Proxy Statement”):

(1) to elect the three Class II director nominees named in the Proxy Statement to serve until the 2029 Annual Meeting of Stockholders and until their successors are duly elected and qualified (“Proposal 1”);

(2) to approve an amendment and restatement of our Amended and Restated 2024 Equity Incentive Plan to increase the number of shares available for issuance by 425,000 shares and to extend the plan term (“Proposal 2”);

(3) to approve, on a non-binding, advisory basis, the compensation of our named executive officers (“Proposal 3”);

(4) to ratify the selection of RSM US LLP as our independent registered public accounting firm for the year ending December 31, 2026 (“Proposal 4”); and

(5) to transact any other matters that may properly come before the Annual Meeting or any adjournments or postponements thereof.

Our Board of Directors (the “Board”) has fixed April 10, 2026 as the record date for the Annual Meeting. Only stockholders of record at the close of business on that date will be entitled to notice of, and to vote at, the Annual Meeting or any adjournment or postponement thereof.

Instructions for accessing the virtual Annual Meeting are provided in the Proxy Statement. We believe that holding the Annual Meeting online via a live audio webcast expands stockholder access, improves communications, and lowers our costs while reducing the environmental impact of the meeting. Stockholders will be able to listen to the Annual Meeting live online, submit questions and vote their shares virtually.

By Order of the Board,

Saul R. Laureles

Chief Legal Officer and Corporate Secretary

Houston, Texas

April 24, 2026

Whether or not you expect to participate in the virtual Annual Meeting, please vote as promptly as possible in order to ensure your representation at the Annual Meeting. You may vote online or, if you requested printed copies of the proxy materials, by telephone or by using the proxy card or voting instruction form provided with the printed proxy materials.

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PROXY OVERVIEW

ANNUAL MEETING OF STOCKHOLDERS

To Be Held on Wednesday, June 3, 2026

“Thank you for being a Stem stockholder. No matter how large or small your holdings, your vote is important to us. We encourage you to vote in accordance with the Board’s recommendations.” —David Buzby, Chairman of the Board

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TABLE OF CONTENTS

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LEGAL MATTERS

Important Notice Regarding the Availability of Proxy Materials for the 2026 Annual Meeting of Stockholders to Be Held on June 3, 2026. The Proxy Statement and our Annual Report on Form 10-K for the year ended December 31, 2025 are available atwww.proxyvote.com.

Forward-Looking Statements. The Proxy Statement may contain “forward-looking statements” within the meaning of the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995, which statements are subject to substantial risks and uncertainties and are based on estimates and assumptions. All statements other than statements of historical fact included in the Proxy Statement are forward-looking statements, including statements about the Company’s Board of Directors, corporate governance practices, executive compensation program, equity compensation utilization, and environment, social, and governance initiatives. In some cases, you can identify forward-looking statements by terms such as “may,” “might,” “will,” “objective,” “intend,” “should,” “could,” “can,” “would,” “expect,” “believe,” “design,” “estimate,” “predict,” “potential,” “plan,” or the negative of these terms, and similar expressions intended to identify forward-looking statements. These statements involve known and unknown risks, uncertainties, and other factors that could cause our actual results or outcomes to differ materially from the forward-looking statements expressed or implied in the Proxy Statement. Such risks, uncertainties, and other factors include those identified in the Company’s Annual Report on Form 10-K for the year ended December 31, 2025 filed with the U.S. Securities and Exchange Commission (“SEC”) and other subsequent documents we file with the SEC. The Company expressly disclaims any obligation to update or alter any statements whether as a result of new information, future events, or otherwise, except as required by law.

Website References. Website references throughout this document are inactive textual references and provided for convenience only, and the content on the referenced websites is not incorporated herein by reference and does not constitute a part of the Proxy Statement.

Use of Trademarks. Trademarks of Stem, Inc. include Stem, PowerTrack™, PowerTrack Sage™, Athena® a registered-trademark, and Athena’s trademarked applications include “Analyzer™,” “Supervisor™,” “Explorer™,” and “PowerBidder™.” Other names and brands may be claimed as the property of others.

Company References. Unless the context otherwise requires, references in the Proxy Statement to “Stem,” “we,” “us,” “our,” or the “Company” refer to Stem, Inc. and its consolidated subsidiaries. The Company was originally known as Star Peak Energy Transition Corp. (“STPK”). On April 28, 2021, we merged with an affiliate of STPK (the “Merger”).

Reverse Stock Split. Effective June 23, 2025, the Company effected a reverse stock split of all outstanding shares of the Company’s common stock at a ratio of 1-for-20. Unless otherwise specified, all share amounts and related figures (as applicable) reported in this Proxy Statement are presented on a post-split basis.

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1400 Post Oak Boulevard, Suite 560, Houston, Texas 77056

PROXY STATEMENT

FOR THE 2026 ANNUAL MEETING OF STOCKHOLDERS

QUESTIONS AND ANSWERS ABOUT THE PROXY MATERIALS AND VOTING

What Is the Purpose of These Proxy Materials?

We are making these proxy materials available to you in connection with the solicitation of proxies by our Board of Directors (the “Board”) for use at our 2026 Annual Meeting of Stockholders (the “Annual Meeting”), to be held virtually on June 3, 2026 at 10:00 a.m. Central Time, or at any other time following adjournment or postponement thereof. You are invited to participate in the Annual Meeting and to vote on the proposals described in this Proxy Statement. The proxy materials will be first made available to our stockholders on or about April 24, 2026.

Why Did I Receive a Notice of Internet Availability?

Pursuant to SEC rules, we are furnishing the proxy materials to our stockholders primarily via the Internet instead of mailing printed copies. This process allows us to expedite our stockholders’ receipt of proxy materials, lower the costs of printing and mailing the proxy materials, and reduce the environmental impact of our Annual Meeting. If you received a Notice of Internet Availability of Proxy Materials (the “Notice”), you will not receive a printed copy of the proxy materials unless you request one. The Notice provides instructions on how to access the proxy materials for the Annual Meeting via the Internet, how to request a printed set of proxy materials, and how to vote your shares.

Why Are We Holding a Virtual Annual Meeting?

We have adopted a virtual meeting format for the Annual Meeting to provide a consistent experience to all stockholders regardless of geographic location. We believe this expands stockholder access, improves communications, and lowers our costs, while reducing the environmental impact of the meeting. In structuring our virtual Annual Meeting, our goal is to enhance rather than constrain stockholder participation in the meeting, and we have designed the meeting to provide stockholders with the same rights and opportunities to participate as they would have at an in-person meeting.

Who Can Vote?

Only stockholders of record at the close of business on April 10, 2026 (the “Record Date”) are entitled to notice of the Annual Meeting and to vote on the proposals described in this Proxy Statement. At the close of business on the Record Date, 8,567,840 shares of our common stock were issued and outstanding.

What Is the Difference between Holding Shares of Common Stock as a Registered Stockholder and as a Beneficial Owner?

If your shares of common stock are registered directly in your name with our transfer agent, Computershare Trust Company, N.A., you are considered to be, with respect to those shares of common stock, the registered stockholder, and these proxy materials are being sent directly to you by us.

If your shares of common stock are held by a broker, fiduciary, or custodian, you are considered the beneficial owner of shares of common stock held in “street name,” and these proxy materials are being forwarded to you from that broker, fiduciary, or custodian.

How Can I Participate in the Virtual Annual Meeting?

Only stockholders of record and beneficial owners of shares of our common stock as of the close of business on April 10, 2026, the Record Date, may attend and participate in the virtual Annual Meeting, including to vote and ask questions. Because the Annual Meeting is solely virtual, you will not be able to attend the Annual Meeting physically in person.

If you are the beneficial owner of shares held of record (i.e. in “street name”) by a broker, bank, or other nominee, you will receive voting instructions from your broker, bank, or other nominee. If your voting instruction form or Notice indicates that you may vote those shares throughwww.proxyvote.com, then you may access, participate in and vote at the Annual Meeting with the 16-digit access code indicated on that voting instruction form or Notice. Otherwise, stockholders who hold their shares in street name should contact their bank, broker or other nominee (preferably at least five days before the Annual Meeting) and obtain a “legal proxy” in order to be able to attend, participate in or vote at the Annual Meeting.

If you are the stockholder of record, you may vote and ask questions at the meeting by logging on to the meeting website atwww.virtualshareholdermeeting.com/STEM2026, enter the control number found on your proxy card or Notice, and follow the instructions on the website.

We will endeavor to answer as many stockholder-submitted questions as time permits that comply with the Annual Meeting rules of conduct. We reserve the right to edit profanity or other inappropriate language and to exclude questions regarding topics that are not pertinent to meeting matters or Company business. If we receive substantially similar questions, we may group such questions together and provide a single response to avoid repetition.

The meeting webcast will begin promptly at 10:00 a.m. Central Time. Online check-in will begin approximately 15 minutes before then. We encourage you to allow ample time for check-in procedures. If you experience technical difficulties during the check-in process or during the meeting, please call the number listed on the meeting website for technical support. Additional information regarding the rules and procedures for participating in the Annual Meeting will be set forth in our meeting rules of conduct, which stockholders can view during the meeting at the meeting website.

What Am I Voting on?

The proposals to be voted on at the Annual Meeting are as follows:

(a)to elect the three Class II director nominees named in the Proxy Statement to serve until the 2029 Annual Meeting of Stockholders and until their successors are duly elected and qualified (“Proposal 1”);

(b)to approve an amendment and restatement of our Amended and Restated 2024 Equity Incentive Plan to increase the number of shares available for issuance by 425,000 shares and to extend the plan term (“Proposal 2”);

(c)to approve, on a non-binding, advisory basis, the compensation of our named executive officers (“Proposal 3”);

(d)to ratify the selection of RSM US LLP as our independent registered public accounting firm for the year ending December 31, 2026 (“Proposal 4”); and

(e)to transact any other matters that may properly come before the Annual Meeting or any adjournments or postponements thereof.

How Does the Board Recommend That I Vote?

The Board recommends that you vote your shares “FOR” each director nominee in Proposal 1 and “FOR” Proposals 2 through 4.

What If Another Matter Is Properly Brought before the Annual Meeting?

As of the date of filing this Proxy Statement, the Board knows of no other matters that will be presented for consideration at the Annual Meeting. If any other matters are properly brought before the Annual Meeting, it is the intention of the persons named as proxies in the proxy card to vote on such matters in accordance with their best judgment.

How Many Votes Do I Have?

Each share of common stock is entitled to one vote on each proposal to be voted on at the Annual Meeting.

What Does It Mean If I Receive More Than One Set of Proxy Materials?

If you receive more than one set of proxy materials, your shares may be registered in more than one name or held in different accounts. Please cast your vote with respect to each set of proxy materials that you receive to ensure that all of your shares are voted.

How Do I Vote?

If you are the registered stockholder, you may vote your shares online during the virtual Annual Meeting (see “How Can I Participate in the Virtual Annual Meeting?” above) or by proxy in advance of the Annual Meeting by Internet atwww.proxyvote.com or, if you requested paper copies of the proxy materials, by completing and mailing a proxy card or by telephone at 1-800-690-6903. Even if you plan to attend the Annual Meeting, we recommend that you also submit your vote as early as possible in advance so that your vote will be counted if you later decide not to, or are unable to, virtually attend the Annual Meeting.

If you are the beneficial owner, you will receive voting instructions from your broker, bank, or other nominee. You must follow the voting instructions provided by your broker, bank, or other nominee in order to instruct your broker, bank, or other nominee how to vote your shares. The availability of Internet and telephone voting options will depend on the voting process of your broker, bank, or other nominee. You may not vote your shares live at the Annual Meeting unless you obtain a legal proxy from your broker, bank, or other nominee.

What Happens If I Do Not Vote?

If you are the registered stockholder and do not vote in one of the ways described above, your shares will not be voted at the Annual Meeting and will not be counted toward the quorum requirement.

If you are the beneficial owner and do not direct your broker, fiduciary, or custodian how to vote your shares, your broker, fiduciary, or custodian will only be able to vote your shares with respect to proposals considered to be “routine.” Your broker, fiduciary, or custodian is not entitled to vote your shares with respect to “non-routine” proposals, which we refer to as a “broker non-vote.” Whether a proposal is considered routine or non-routine is subject to stock exchange rules and final determination by the stock exchange. Even with respect to routine matters, some brokers are choosing not to exercise discretionary voting authority. As a result, we urge you to direct your broker, fiduciary, or custodian how to vote your shares on all proposals to ensure that your vote is counted.

What If I Sign and Return a Proxy Card or Otherwise Vote but Do Not Indicate Specific Choices?

The shares represented by each signed and returned proxy will be voted at the Annual Meeting by the persons named as proxies in the proxy card in accordance with the instructions indicated on the proxy card. However, if you are the registered stockholder and sign and return your proxy card without giving specific instructions, the persons named as proxies in the proxy card will vote your shares in accordance with the recommendations of the Board. Your shares will be counted toward the quorum requirement.

If you are the beneficial owner and sign and return your voting instruction form without giving specific instructions, your broker, fiduciary, or custodian will only be able to vote your shares with respect to proposals considered to be

“routine.” Your broker, fiduciary, or custodian is not entitled to vote your shares with respect to “non-routine” proposals, resulting in a broker non-vote with respect to such proposals.

Can I Change My Vote after I Submit My Proxy?

If you are the registered stockholder, you may revoke your proxy at any time before the final vote at the Annual Meeting in any one of the following ways:

(1) you may complete and submit a new proxy card, but it must bear a later date than the original proxy card;

(2) you may submit new proxy instructions via telephone or the Internet;

(3) you may send a timely written notice that you are revoking your proxy to our Corporate Secretary at the address set forth on the first page of this Proxy Statement; or

(4) you may vote by attending the Annual Meeting virtually. However, your virtual attendance at the Annual Meeting will not, by itself, revoke your proxy.

Your last submitted vote is the one that will be counted.

If you are the beneficial owner, you must follow the instructions you receive from your broker, fiduciary, or custodian with respect to changing your vote.

What Is the Quorum Requirement?

The holders of one-third of the shares of common stock outstanding and entitled to vote at the Annual Meeting must be present at the Annual Meeting, either virtually or represented by proxy, to constitute a quorum. A quorum is required to transact business at the Annual Meeting.

Your shares will be counted toward the quorum only if you submit a valid proxy (or a valid proxy is submitted on your behalf by your broker, fiduciary, or custodian) or if you attend the Annual Meeting virtually and vote. Abstentions and broker non-votes will be counted toward the quorum requirement. If there is no quorum, the chairman of the Annual Meeting or the holders of a majority of shares of common stock virtually present at the Annual Meeting, either personally or by proxy, may adjourn the Annual Meeting to another time or date.

How Many Votes Are Required to Approve Each Proposal and How Are Votes Counted?

Votes will be counted by a representative of Carideo Group, who has been appointed as the independent Inspector of Elections for the Annual Meeting.

Proposal 1: Election of Directors

A nominee will be elected as a director at the Annual Meeting if the nominee receives a plurality of the votes cast “FOR” their election. “Plurality” means that the individuals who receive the largest number of votes cast “FOR” are elected as directors. Broker non-votes, if any, and votes that are withheld will not be counted as votes cast on the proposal and will have no effect on the outcome of the election. Stockholders do not have cumulative voting rights for the election of directors.

Proposal 2: Approval of an Amendment and Restatement of the 2024 Equity Incentive Plan

The affirmative vote of a majority of shares of common stock present or represented at the Annual Meeting and entitled to vote thereon is required for the approval of this proposal. Abstentions will have the same effect as a vote “AGAINST” the proposal. Broker non-votes, if any, will have no effect on the outcome of this proposal.

Proposal 3: Non-binding, Advisory Approval of Named Executive Officer Compensation

The affirmative vote of a majority of shares of common stock present or represented at the Annual Meeting and entitled to vote thereon is required for the approval of this proposal. Abstentions will have the same effect as a vote “AGAINST” the proposal. Broker non-votes, if any, will have no effect on the outcome of this proposal.

Proposal 4: Ratification of Independent Auditor Selection

The affirmative vote of a majority of shares of common stock present or represented at the Annual Meeting and entitled to vote thereon is required for the approval of this proposal. Abstentions will have the same effect as a vote “AGAINST” the proposal. Broker non-votes, if any, will have no effect on the outcome of this proposal.

Who Is Paying for This Proxy Solicitation?

We will pay the costs associated with the solicitation of proxies, including the preparation, assembly, printing, and mailing of the proxy materials. We have retained D.F. King & Co., Inc. and its affiliate to assist in the solicitation of proxies for a fee estimated at $5,500 plus reasonable expenses. Our employees, officers, and directors may solicit proxies in person or via telephone or the Internet. We will not pay additional compensation for any of these services. We may also reimburse brokers, fiduciaries, or custodians for the cost of forwarding proxy materials to beneficial owners of shares of common stock held in “street name.”

How Can I Find out the Voting Results?

We expect to announce preliminary voting results at the Annual Meeting. We will disclose final voting results in a Current Report on Form 8-K that we will file with the SEC within four business days after the Annual Meeting.