Eos Energy Enterprises Inc

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To the shareholders and the Board of Directors of Eos Energy Enterprises, Inc.

Opinion on the Financial Statements

We have audited the accompanying consolidated balance sheets of Eos Energy Enterprises, Inc. (the "Company") as of December 31, 2023 and 2022, the related consolidated statements of operations and comprehensive loss, shareholders’ (deficit) equity, and cash flows, for each of the two years in the period ended December 31, 2023, and the related notes (collectively referred to as the "financial statements"). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2023 and 2022, and the results of its operations and its cash flows for each of the two years in the period ended December 31, 2023, in conformity with accounting principles generally accepted in the United States of America.

Going Concern

The accompanying financial statements have been prepared assuming that the Company will continue as a going concern. As discussed in Note 1 to the financial statements, the Company has suffered recurring losses from operations and may be unable to remain in compliance with a financial covenant required by a borrowing arrangement absent the Company’s ability to secure additional outside capital, which raises substantial doubt about its ability to continue as a going concern. Management’s plans in regard to these matters are also described in Note 1. The financial statements do not include any adjustments that might result from the outcome of this uncertainty.

Basis for Opinion

These financial statements are the responsibility of the Company's management. Our responsibility is to express an opinion on the Company's financial statements 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 the 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 audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. The Company is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. As part of our audits, we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Company’s internal control over financial reporting. Accordingly, we express no such opinion.

Our audits 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. We believe that our audits provide a reasonable basis for our opinion.

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.

Convertible Notes Payable and Warrants Liability -Refer to Notes 12 and 13 to the financial statements

Critical Audit Matter Description

The Company’s 2021 Convertible Notes and AFG Convertible Notes (collectively "the Convertible Notes") contain embedded conversion features that are required to be bifurcated from the Convertible Notes and measured at fair value at each reporting period.

The Company estimates the fair value of the embedded conversion feature using a binomial lattice model at the inception and on subsequent valuation dates. This model incorporates inputs such as the stock price of the Company, dividend yield, risk-free interest rate, the effective debt yield, and expected volatility. The effective debt yield and the expected volatility involve unobservable inputs.

The Company’s April 2023 Transaction, May 2023 Transaction, and the December 2023 Public Offering include warrants that are required to be measured at fair value at each reporting period. The Company estimates the fair value of the warrants using a Black-Scholes model at the inception and on subsequent valuation dates. This model incorporates inputs such as the stock price of the Company, exercise price, risk-free interest rate, expected volatility, and time to expiration. The expected volatility involves unobservable inputs.

Unlike the fair value of financial instruments that are readily observable and therefore more easily independently corroborated, the valuation of the embedded conversion features and warrants is inherently subjective and involves the use of complex modeling tools. Auditing the fair value of the embedded conversion features and warrants requires a high degree of auditor judgment and an increased extent of effort, including the need to involve our fair value specialists.

How the Critical Audit Matter Was Addressed in the Audit

Our audit procedures related to the valuation of (1) the embedded conversion features in the Convertible Notes and (2) warrants included the following, among others:

•With the assistance of our fair value specialists, we evaluated the reasonableness of management’s valuation methodology and the significant assumptions used in determining the fair value of the embedded conversion features and warrants by:

◦Testing the source information underlying the fair value of the embedded conversion features and warrants and the mathematical accuracy of the calculations.

◦Developing an independent estimate of the inputs and compared those to the inputs used in the fair value of the embedded conversion features and warrants.

•We evaluated the competency and objectivity of management’s expert engaged by the Company to perform the valuation of the embedded conversion features and warrants.

/s/Deloitte & Touche LLP

New York, NY

March 4, 2024

We have served as the Company's auditor since 2017.