Ameresco, Inc.

To the Stockholders and the Board of Directors of Ameresco, Inc.

Opinions on the Financial Statements and Internal Control Over Financial Reporting

We have audited the accompanying consolidated balance sheets of Ameresco, Inc. (the Company) as of December 31, 2025 and 2024, and the related consolidated statements of income, comprehensive income, changes in redeemable non-controlling interests and stockholders' equity and cash flows for each of the three years in the period ended December 31, 2025, and the related notes (collectively, the financial statements). We also have audited the Company’s internal control over financial reporting as of December 31, 2025, based on criteria established in Internal Control — Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission in 2013.

In our opinion, the financial statements referred to above present fairly, in all material respects, the financial position of the Company as of December 31, 2025 and 2024, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2025, in conformity with accounting principles generally accepted in the United States of America. Also in our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of December 31, 2025, based on criteria established in Internal Control — Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission in 2013.

Basis for Opinions

The Company's management is responsible for these financial statements, for maintaining effective internal control over financial reporting, and for its assessment of the effectiveness of internal control over financial reporting, included in the accompanying Management’s Annual Report on Internal Control over Financial Reporting. Our responsibility is to express an opinion on the Company's financial statements and an opinion on the Company's internal control over financial reporting based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audits to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud, and whether effective internal control over financial reporting was maintained in all material respects.

Our audits of the financial statements included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. Our audit of internal control over financial reporting included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, and testing and evaluating the design and operating effectiveness of internal control based on the assessed risk. Our audits also included performing such other procedures as we considered necessary in the circumstances. We believe that our audits provide a reasonable basis for our opinions.

Definition and Limitations of Internal Control Over Financial Reporting

A company's internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company's internal control over financial reporting includes those policies and procedures that (1) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (2) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (3) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use or disposition of the company's assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

Critical Audit Matter

The critical audit matter communicated below is a matter arising from the current period audit of the financial statements that was communicated or required to be communicated to the audit committee and that: (1) relates to accounts or disclosures that are material to the financial statements and (2) involved our especially challenging, subjective or complex judgments. The communication of critical audit matters does not alter in any way our opinion on the financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing a separate opinion on the critical audit matter or on the accounts or disclosures to which it relates.

Revenue from Contracts with Customers—Project Revenue

As described in Notes 2 and 3 to the financial statements, the Company’s projects line of business, which relates to the construction of energy efficiency projects, including the design, engineering and installation of technologies and techniques to improve energy efficiency and control the operation of a building’s energy- and-water-consuming systems, recognized revenue of $1.49 billion during the year ended December 31, 2025. Typically, the Company provides a service of integrating a complex set of tasks and components such as design, engineering, construction management, and equipment procurement for a project contract. The Company’s project revenues are generated from long-term contracts whereby revenue is recognized over time using the cost-based input method. The Company uses total costs incurred on the project relative to the total expected costs to estimate progression towards the satisfaction of the performance obligation.

Estimating the amount of project revenue to record from the Company’s long-term contracts requires management’s judgment in estimating final construction contract profits, which are driven by the total estimated consideration payable by the customer and total estimated contract costs. The Company estimates the total consideration payable by the customer when the contracts contain variable consideration provisions, which can include liquidated damages and/or penalties, based on the most likely amount anticipated to be recognized for transferring the promised goods or services. As a result, the Company may constrain revenue to the extent that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. Anticipated contract costs can be incurred over several years and are largely determined based on negotiated or estimated purchase contract terms and consider factors such as historical performance, seasonal and construction schedule risks, estimated subcontractor costs and contingency costs.

We identified the Company’s accounting for revenue recognition from the project line of business to be a critical audit matter due to the significant judgments used by management related to the estimation of final construction profits. Estimating the final construction profit on these long-term contracts requires management to develop estimates of the total consideration payable by the customer, when contracts contain variable consideration provisions, as well as total expected contract costs, including costs associated with labor, materials, equipment, subcontracting and outside engineering cost. Auditing management’s estimates and assumptions involved a high degree of auditor judgment and increased audit effort due to the impact these assumptions have on the revenue recognized.

Our audit procedures related to project revenue included the following, among others:

•We obtained an understanding of the relevant controls related to the recognition of project revenue and tested such controls for design and operating effectiveness, including controls over the determination of the final estimated construction profit, which includes management’s review of the assumptions and key inputs used to recognize revenue on project contracts using the cost-to-cost input method, including costs associated with labor, materials, equipment, subcontracting and outside engineering along with estimates of total consideration payable when contracts contain variable consideration provisions.

•We performed substantive analytical procedures on the Company’s project revenue line of business, with a focus on significant changes in gross margin, contract budgets and contract pricing from the prior year, on contracts open in both the current year and prior year.

•We selected a sample of project contracts and evaluated the estimates of total costs for each of the project contracts by:

◦Testing the initial project budget by the development of an independent contract profit margin expectation for the projects combined with inquiry with the project management team and/or comparing selected items from the underlying budget to the source information used to develop the project budget.

◦Evaluating management’s judgments related to the Company’s ability to achieve both the estimates of final construction contract profit and the project timeline as well as management’s estimates of total consideration payable, when contracts contain variable consideration, by performing corroborating inquiries with Company personnel, including project managers, and comparing the estimates to documentation such as management’s internal budgets and contract terms.

◦Confirming project progression with customers, including identification of any delays in the project timeline.

/s/ RSM US LLP

We have served as the Company's auditor since 2010.

Boston, Massachusetts

March 3, 2026