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, 2025 and 2024, the related consolidated statements of operations and comprehensive loss, shareholders’ deficit, and cash flows, for each of the two years in the period ended December 31, 2025, 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, 2025 and 2024, and the results of its operations and its cash flows for each of the two years in the period ended December 31, 2025, in conformity with accounting principles generally accepted in the United States of America.

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 Matters

The critical audit matters communicated below are matters arising from the current-period audit of the financial statements that were communicated or required to be communicated to the audit committee and that (1) relate 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 matters below, providing a separate opinion on the critical audit matters or on the accounts or disclosures to which they relate.

Convertible Notes and Warrants Liability - Refer to Notes 13, 14 and 16 to the financial statements

Critical Audit Matter Description

On June 3, 2025, the Company issued the May 2025 Convertible Notes and used a portion of the proceeds to extinguish the 2021 Convertible Notes. On July 29, 2025, the Company amended the AFG Convertible Notes, and during August 2025 and November 2025 settled the AFG Convertible Notes in shares of common stock. On November 24, 2025, the Company issued the November 2025 Convertible Notes, and subsequent to the issuance of the November 2025 Convertible Notes settled a portion of the May 2025 Convertible Notes in cash.

Auditing the accounting for the (1) issuance of the May 2025 Convertible Notes and the November 2025 Convertible Notes, (2) extinguishment of the 2021 Convertible Notes, (3) amendment and subsequent conversion of the AFG Convertible Notes, and (4) partial settlement of the May 2025 Convertible Notes, required a high degree of auditor judgment and an increased extent of effort, including the need to involve professionals in our firm with expertise in accounting for financial instruments.

The Company’s 2021 Convertible Notes, the AFG Convertible Notes, and the November 2025 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 inception and at each valuation date. The Company estimates the fair value of the embedded conversion features using a binomial lattice model at 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 included 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 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 warrants and the embedded conversion features in the Convertible Notes is inherently subjective and involves the use of complex modeling tools. Auditing the fair value of warrants and the embedded conversion features in the Convertible Notes required 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 (1) accounting for (a) the issuance of the May 2025 Convertible Notes and the November 2025 Convertible Notes, (b) the extinguishment of the 2021 Convertible Notes, (c) the amendment and subsequent conversion of the AFG Convertible Notes, and (d) the partial settlement of the May 2025 Convertible Notes, and (2) valuation of the warrants and embedded conversion features in the Convertible Notes, included the following, among others:

•With the assistance of professionals in our firm with expertise in accounting for financial instruments, we evaluated the appropriateness of management’s accounting conclusions related to (a) issuance of the May 2025 Convertible Notes and the November 2025 Convertible Notes, (b) the extinguishment of the 2021

Convertible Notes, (c) the amendment and subsequent conversion of the AFG Convertible Notes, and (d) the partial settlement of the May 2025 Convertible Notes.

•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 warrants and the embedded conversion features in the Convertible Notes by::

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

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

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

Financial Instruments Associated with the Credit and Securities Purchase Transaction - Refer to Notes 3, 13, 14 and 16 to the financial statements

Critical Audit Matter Description

On June 21, 2024, the Company entered into a (1) credit and guaranty agreement (the “Credit Agreement”) with CCM Denali Debt Holdings, LP, and (2) Securities Purchase Agreement (the “SPA”) with CCM Denali Equity Holdings, LP (collectively, CCM Denali Debt Holdings, LP and CCM Denali Equity Holdings, LP referred to as “Cerberus”) (collectively, the Credit Agreement and the SPA referred to as “Cerberus Agreements”).

Under the terms of the Credit Agreement, Cerberus agreed to provide a (1) $210.5 million secured multi-draw facility to be made in four installments (the “Delayed Draw Term Loan”) upon the achievement of certain performance milestones on dates specified in the Credit Agreement, and (2) $105.0 million revolving credit facility, to be made available beginning June 21, 2026, at Cerberus’ sole discretion and only if the Delayed Draw Term Loan is fully funded. The Delayed Draw Term Loan was fully funded in 2025.

Under the terms of the SPA, during 2024 and 2025 the Company issued the following (1) a warrant to purchase 43,276,194 shares of Common Stock (the “SPA Warrant”), (2) 59 shares of Series A-1 Preferred Stock, and (3) preferred stock or warrants upon the achievement of performance milestones on dates specified in the Credit Agreement, up to an aggregate of 33.0% ownership limitation on a fully diluted basis at such time the Delayed Draw Term Loan is fully drawn (the “Contingent Warrants”). The Contingent Warrants were settled in Preferred Stock upon the successful funding of the Delayed Draw Term Loan on dates specified in the Credit Agreement.

The Company estimates the fair value of the debt issued under the Delayed Draw Term Loan at inception and on subsequent valuation dates using a discounted cash flow method, based on the contractual cash flows discounted at the effective debt yield. The effective debt yield involves unobservable inputs.

The Company estimates the fair value for the SPA warrant issued under the Securities Purchase Agreement at inception and on subsequent valuation dates based on its intrinsic value, using the Company’s common stock closing price adjusted by a discount for lack of marketability (“DLOM”), less the exercise price. The DLOM involves unobservable inputs.

The Company estimates the fair value of the Contingent Warrants (issued under the Securities Purchase Agreement), which were subsequently settled in Preferred Stock, on subsequent valuation dates based on the Company’s common stock closing price adjusted by a DLOM using Black-Scholes option pricing model. The expected volatility, and the DLOM involve unobservable inputs.

Unlike the fair value of financial instruments that are readily observable and therefore more easily independently corroborated, the valuation of the financial instruments associated with the Cerberus Agreements is inherently subjective and involves the use of complex modeling tools. Auditing the fair value of the financial instruments associated with the Cerberus Agreements required 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 the financial instruments associated with the Cerberus Agreements 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 financial instruments issued under the Cerberus Agreements by:

◦Testing the source information underlying the fair value of the financial instruments issued under the Cerberus Agreements 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 financial instruments issued under the Cerberus Agreements.

•We evaluated the competency and objectivity of management’s expert engaged by the Company to perform the accounting and valuation of the financial instruments associated with the Cerberus Agreements.

/s/Deloitte & Touche LLP

New York, NY

February 26, 2026

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