Ameresco : 2024 Proxy

Proxy Statement

for 2024 Annual Meeting

NOTICE OF 2024 ANNUAL MEETING OF STOCKHOLDERS

TO BE HELD ON JUNE 4, 2024

To Our Stockholders:

The 2024 annual meeting of stockholders of Ameresco, Inc., a Delaware corporation, will be held on June 4, 2024, at 10:00 a.m., Eastern Time, for the following purposes:

1. To elect the three (3) nominees identified in the accompanying proxy statement as members of our board of directors to serve as class II directors for a term of three years.
2. To ratify the appointment of RSM US LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2024.
3. To approve an amendment to the 2017 Employee Stock Purchase Plan to increase the number of shares reserved for issuance under the plan to 575,000.
4. To transact other business, if any, that may properly come before the annual meeting and any adjournment thereof.

The foregoing items of business are more fully described in the Proxy Statement. Only stockholders who owned our Class A common stock or Class B common stock at the close of business on April 10, 2024, can vote at the Annual Meeting or any adjournments or postponements that take place.

Our board of directors, or board, recommends that you vote FOR the election of the director nominees named in Proposal 1, FOR the ratification of the appointment of RSM US LLP as our independent registered public accounting firm as described in Proposal 2, and FOR the approval of an amendment to the 2017 Employee Stock Purchase Plan as described in Proposal 3.

This year's Annual Meeting will be a completely virtual meeting of stockholders, conducted via an online platform. The Annual Meeting can be accessed by visiting www.virtualshareholdermeeting.com/AMRC2024, where you will be able to listen to the meeting live, submit questions and vote online.

We are pleased to utilize the Securities and Exchange Commission, or SEC, rules that allow issuers to furnish proxy materials to their stockholders on the Internet. On or about April 23, 2024, we will mail to our stockholders of record as of April 10, 2024 (other than those who previously requested electronic or paper delivery on an ongoing basis) a Notice Regarding the Availability of Proxy Materials, or Notice, with instructions for accessing the proxy materials and voting over the Internet, by telephone or mobile device or by mail. The Notice also provides information on how stockholders may request paper copies of our proxy materials. We believe electronic delivery of our proxy materials and our 2023 Annual Report will help us reduce the environmental impact and costs of printing and distributing paper copies and improve the speed and efficiency by which our stockholders can access these materials.

Your vote is very important. Whether or not you plan to attend the virtual Annual Meeting, we encourage you to read our proxy materials and submit your proxy or voting instructions as soon as possible over the Internet, by telephone or mobile device or by mail.

By Order of the Board of Directors,

David J. Corrsin

Secretary

April 23, 2024

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TABLE OF CONTENTS

GENERAL INFORMATION ABOUT THE MEETING AND VOTING	1
PROPOSAL 1-ELECTION OF DIRECTORS	4
PROPOSAL 2-RATIFICATION OF THE SELECTION OF OUR INDEPENDENT REGISTERED PUBLIC
ACCOUNTING FIRM	5
Audit and Other Fees	5
Policy on Pre-Approval of Audit and Non-Audit Services	5
Audit Committee Report	6
PROPOSAL 3-APPROVAL OF AN AMENDMENT TO THE 2017 EMPLOYEE STOCK PURCHASE PLAN	7
STOCK OWNERSHIP AND RELATED INFORMATION	12
Stock Ownership	12
Equity Compensation Plan Information	14
Delinquent Section 16(a) Reports	14
CORPORATE GOVERNANCE	15
Board of Directors	15
Corporate Governance Guidelines	23
Anti-hedging and Pledging Policies	23
Code of Business Conduct and Ethics	23
Stock Ownership Guidelines	23
Clawback Policy	24
Rule 10b-5 Sales Plans	24
Compensation Committee Interlocks and Insider Participation	24
EXECUTIVE COMPENSATION AND RELATED INFORMATION	25
Our Executive Officers and Our Named Executive Officers	25
Compensation Discussion And Analysis	26
Risk Considerations in our Compensation Program	32
Compensation Committee Report	33
Executive Compensation Tables	34
Pay Ratio	37
Pay Versus Performance	38
CERTAIN RELATIONSHIPS AND RELATED PERSON TRANSACTIONS	43
ADDITIONAL INFORMATION	43
APPENDIX A	A-1

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AMERESCO, INC.

111 Speen Street, Suite 410,

Framingham, Massachusetts 01701

PROXY STATEMENT FOR 2024 ANNUAL MEETING OF STOCKHOLDERS

TO BE HELD ON JUNE 4, 2024

GENERAL INFORMATION ABOUT THE MEETING AND VOTING

This proxy statement is furnished in connection with the solicitation of proxies by the board of directors of Ameresco, Inc. for use at the 2024 annual meeting of stockholders, or the Annual Meeting, to be held on June 4, 2024, at 10:00 a.m., local time, and at any adjournments of the Annual Meeting. We will hold our annual meeting of stockholders in virtual meeting, via live audio webcast. You may virtually attend the meeting and vote your shares by visiting www.virtualshareholdermeeting.com/AMRC2024.

In this proxy statement, unless expressly stated or the context otherwise requires, the use of "Ameresco," "the Company," "our," "we," or "us" refers to Ameresco, Inc.

We are mailing the Notice Regarding the Availability of Proxy Materials, or the Notice, to our stockholders of record as of April 10, 2024, or the Record Date, on or about April 23, 2024. In addition, we have provided brokers, dealers, banks, voting trustees and their nominees, at our expense, with additional copies of our proxy materials and the 2023 Annual Report so that our record holders can supply these materials to the beneficial owners of shares of our Class A common stock and Class B common stock as of the Record Date. The proxy statement and our annual report to stockholders are available for viewing, printing and downloading online at the "Investor Relations - Annual Meeting" section of our website at www.ameresco.com.

Information about the proxy process and voting

Record Date, Voting Rights and Outstanding Shares

Our board of directors has fixed April 10, 2024 as the record date for determining the holders of our capital stock who are entitled to vote at the annual meeting.

We have two classes of capital stock issued and outstanding: Class A common stock, $.0001 par value per share, and Class B common stock, $.0001 par value per share. We refer to our Class A common stock and our Class B common stock collectively as our common stock.

With respect to all of the matters submitted for vote at the Annual Meeting, each share of Class A common stock is entitled to one vote and each share of Class B common stock is entitled to five votes.

Our Class A common stock and Class B common stock will vote as a single class on each of the matters submitted at the Annual Meeting. On April 10, 2024, there were outstanding and entitled to vote 34,330,161 shares of Class A common stock and 18,000,000 shares of Class B common stock.

Quorum

In order for business to be conducted at the Annual Meeting, a quorum must be present at the meeting. A quorum for purposes of the Annual Meeting will exist if the holders of a majority of the voting power represented by the common stock issued and outstanding on April 10, 2024 attend the virtual meeting or are represented by proxy at the Annual Meeting. Shares represented by valid proxies, regardless of whether the proxy is noted as casting a vote or abstaining, and broker non-votes (described below) will be treated as present at the Annual Meeting for purposes of determining a quorum. Shares voted by a broker on any item other than a procedural motion will be considered present for purposes of determining a quorum, even if such shares are not voted on every item.

Required Votes

Election of directors (Proposal 1): The three director nominees identified in this proxy statement receiving a plurality, or the highest number, of votes cast, regardless of whether that number represents a majority of the votes cast, will be elected. Only votes "For" will affect the outcome of this proposal.

Ratification of the appointment of RSM US LLP (Proposal 2): The affirmative vote of a majority of the votes cast is needed to ratify the appointment of RSM US LLP as our independent registered public accounting firm for our fiscal year ending December 31, 2024. Abstentions and broker non-votes will have no effect on the outcome of this proposal.

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Approval of an amendment to our 2017 Employee Stock Purchase Plan (Proposal 3): The affirmative vote of a majority of the shares present, in person or represented by proxy, and voting on such matter is required to approve the amendment to the 2017 Employee Stock Purchase Plan.

Voting; Voting by Proxy

Stockholders of Record. If on the Record Date, your shares were registered directly in your name with the transfer agent for our common stock, then you are a stockholder of record. As a stockholder of record, you may vote at the Annual Meeting or by proxy. Whether or not you plan to attend the Annual Meeting, we urge you to vote and submit your proxy in advance of the Annual Meeting by one of the methods below to ensure your vote is counted. To vote by any of these methods, read this Proxy Statement, have your Notice, proxy card, or voting instruction form in hand, and follow the instructions below for your preferred method of voting. Each of these voting methods is available 24 hours per day, seven days per week, but you must vote by 11:59 pm. on June 3, 2024.

By internet

Before the Annual Meeting - go to www.proxyvote.com. During the Annual Meeting - go to www.virtualshareholdermeet ing.com/AMRC2024

By phone

From the United States, U.S. territories and Canada: call 1-800-690-6903

By mail

If you received a paper copy of the proxy materials by mail, mark, sign, date and promptly mail the enclosed proxy card in the postage- paid envelope

By scanning

Scan the QR code using your mobile device to vote via the ProxyVote app

Beneficial Owner (Shares Registered in the Name of a Broker, Bank or Other Agent). If, on the Record Date, your shares were held in an account at a broker, bank or other agent, then you are the beneficial owner of shares held in "street name" and the Notice or these proxy materials are being forwarded to you by that organization. The organization holding your account is considered the stockholder of record for purposes of voting at the Annual Meeting. As a beneficial owner, you have the right to direct your broker, bank or other agent on how to vote the shares in your account. You are also invited to attend the Annual Meeting via the Internet. However, because you are not the stockholder of record, you may not vote your shares at the Annual Meeting unless you request and obtain a valid proxy card from your broker, bank or other agent. Please follow the instructions from your broker, bank or other agent included with these proxy materials, or contact your broker, bank or other agent to request a proxy card.

What are "broker non-votes"?

Broker non-votes occur when a beneficial owner of shares held in "street name" does not give instructions to the broker, bank or other agent holding the shares as to how to vote on matters deemed "non-discretionary." Generally, if shares are held in street name, the beneficial owner of the shares is entitled to give voting instructions to the broker, bank or other agent holding the shares. If the beneficial owner does not provide voting instructions, the broker, bank or other agent can still vote the shares with respect to matters that are considered to be "discretionary," but not with respect to "non- discretionary" matters. In the event that a broker, bank or other agent or other record holder of common stock indicates on a proxy that it does not have discretionary authority to vote certain shares on a particular proposal, then those shares will be treated as broker non-votes with respect to that proposal. Accordingly, if you own shares through a nominee, such as a broker, bank or other agent, please be sure to instruct your nominee how to vote to ensure that your vote is counted on each of the proposals.

Which ballot measures are considered "discretionary" or "non-discretionary?"

The ratification of the appointment of RSM LLP as our independent registered public accounting firm for the year ending December 31, 2024 (Proposal 2) is considered discretionary under applicable rules. A broker, bank or other agent may generally vote on discretionary matters, and therefore no broker non-votes are expected to exist in connection with Proposal 2. The election of directors (Proposal 1) and the amendment to the Employee Stock Purchase Plan (Proposal 3) are considered non-discretionary under applicable rules. A broker, bank or other agent cannot vote without instructions on non-discretionary matters, and therefore there may be broker non-votes on Proposal 1 or Proposal 3.

Discretionary Voting by Proxies on Other Matters

We do not know of any other proposals that may be presented at the Annual Meeting. If another matter is properly presented for consideration at the meeting, the persons named in the accompanying proxy card will exercise their discretion in voting on the matter.

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Can I change my vote after submitting my proxy?

Yes. You can revoke your proxy at any time before the final vote at the Annual Meeting. If you are the record holder of your shares, you may revoke your proxy in any one of three (3) ways:

• You may submit another properly completed proxy with a later date over the Internet, by telephone or mobile device or by mail.
• You may send a written notice that you are revoking your proxy to us at our principal executive offices, 111 Speen Street, Suite 410, Framingham, Massachusetts 01701, Attention: Secretary.
• You may attend the Annual Meeting via the Internet and vote online. Simply attending the Annual Meeting will

not, by itself, revoke your proxy.

If your shares are held by your broker, bank or other agent, you should follow the instructions provided by them.

Voting Results

We will report the voting results from the Annual Meeting in a Current Report on Form 8-K, which we expect to file with the SEC within four business days after the Annual Meeting.

What does it mean if I receive more than one Notice?

If you receive more than one Notice, your shares are registered in more than one name or are registered in different accounts. In order to vote all the shares you own, you must vote pursuant to the instructions on each Notice.

Expenses of Solicitation

We will bear the costs of soliciting proxies. We will, upon request, reimburse brokers, custodians and fiduciaries for reasonable out-of-pocket expenses incurred in forwarding proxy solicitation materials to the beneficial owners of stock held in their names. In addition to solicitations by mail, our directors, officers and employees may solicit proxies from stockholders in person or by other means of communication, including telephone, facsimile and e-mail, without additional remuneration.

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PROPOSAL 1-ELECTION OF DIRECTORS

Our board of directors is divided into three classes, with one class being elected each year and members of each class holding office for a three-year term. We have three (3) class I directors, whose terms expire at our 2026 annual meeting of stockholders; three (3) class II directors, whose terms expire at this Annual Meeting of stockholders; and two (2) class III directors, whose terms expire at our 2025 annual meeting of stockholders. Our board of directors currently consists of eight members.

At this Annual Meeting, our stockholders will have an opportunity to vote for three (3) nominees for class II directors:

• David J. Corrsin,
• George P. Sakellaris, and
• Joseph W. Sutton

each of whom are currently directors of Ameresco. You can find more information about each of the nominees in "Corporate Governance-OurBoard of Directors" below.

If no contrary indication is made, proxies in the accompanying form will be voted "FOR" these three nominees as class II directors. If elected, each of the nominees for class II director will hold office until the 2027 annual meeting of stockholders and until their successor is elected and qualified or until their earlier death, resignation or removal. Each of the nominees has indicated their willingness to serve if elected. However, if any nominee should be unable to serve, then either the persons named in the proxy card may vote the proxy for a substitute nominee if one is nominated by our board of directors, or we may maintain a vacancy on our board of directors until such time as our board of directors can find a suitable candidate to serve on the board, or our board of directors may reduce the number of directors.

Our board of directors recommends a vote FOR each of the three nominees for class II directors.

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