GWH · ESS Tech, Inc.

Agreement Supports Advancement and Real-World Evaluation of ESS’s Non-Lithium Long Duration Energy Storage Energy Base Technology Collaboration Expected to Support Utility and Large-Load Sustainability Objectives, and Clean Energy Goals of Project Participants ESS Tech, Inc. (NYSE: GWH) (ESS, or the Company), a leading manufacturer of long-duration energy storage (LDES) systems for commercial and utility-scale today applications, today announced a collaboration framework with Salt River Project (SRP) and Google for Project New Horizon to advance long-duration energy storage innovation at SRP’s Copper Crossing Energy and Research Center in Florence, Arizona. Project New Horizon is a five-megawatt (MW), 50 megawatt hour (MWh) system that will deploy ESS’ iron flow Energy Base technology and represents a significant commercial validation milestone for the Company’s next-generation, utility-scale platform. The pilot is expected to support SRP’s evaluation of emerging non-lithium LDES

Veteran Energy Storage Commercial Leader to Drive Global Commercial Execution as ESS Strengthens Leadership Team and Scales Deployments ESS Tech, Inc. (NYSE: GWH) (“ESS” or the “Company”), a leading innovator in long-duration energy storage solutions, today announced that Randall “Randy” Selesky has joined the company as Chief Commercial Officer (CCO). In this role, Selesky will lead global commercial strategy, sales, marketing, product management, and business development initiatives as ESS advances commercialization and scales deployment of its long-duration energy storage solutions worldwide. Selesky joins ESS with more than 20 years of leadership in the energy sector, including more than a decade in the battery storage industry. Prior to joining ESS, he served as the Chief Commercial Officer at VoltStorage, where he played a central role in shaping commercial strategy, building partnerships, and guiding the company’s market expansion. Throughout his career, Selesky has been

ESS Tech, Inc. (ESS) (NYSE : GWH), a leading manufacturer of iron flow long-duration energy storage (LDES) systems for commercial- and utility-scale applications, today announced that it will hold a conference call on Thursday, March 5, 2026 at 5:00 p.m. EST to discuss financial results for its fourth quarter and full year 2025 ended December 31, 2025, and will be providing updates on recent organizational changes, commercial progress and customer deployments, and strategic priorities going forward. A press release detailing these results will be issued prior to the call. ESS Tech CEO Drew Buckley and CFO Kate Suhadolnik will host the conference call, followed by a question-and-answer period. The conference call will be accompanied by a presentation, which can be viewed or access following the call via the investor relations section of the Company’s website here . To access the call, please use the following information: Date : Thursday, March 5, 2026 Time: 5:00 p.m. Eastern Time

Acquisition Expands ESS Technology Portfolio and Strengthens Path to Lower-Cost, Scalable Long-Duration Storage Key VoltStorage Executive and Engineering Personnel Join ESS, Strengthening the Commercial and Technical Bench ESS Tech, Inc. (“ESS” or the “Company”), a leading innovator in long-duration energy storage solutions, today announced the acquisition of the intellectual property and assets of VoltStorage GmbH, a pioneer in iron-salt battery technology. This strategic move combines two complementary technologies to deliver the most flexible, cost-effective long-duration energy storage solution available on the market. The combined platform will set a new industry standard for performance, sustainability, and affordability. This acquisition adds VoltStorage’s portfolio of patents and technical development work to ESS’ robust existing intellectual property base. Through the transaction, ESS also gains access to skilled personnel with deep electrochemistry, materials science, and

Recently Appointed CEO Drew Buckley Highlights Recent Commercial Progress, Balance Sheet Actions, and Corporate Governance Updates ESS Tech, Inc. (NYSE: GWH) (the “Company”), a leading manufacturer of long-duration energy storage systems (LDES) for commercial and utility-scale applications, today issued a letter to shareholders from Drew Buckley, Chief Executive Officer. Dear Shareholders, Since assuming the role of Chief Executive Officer at the beginning of 2026, my focus has been on resetting ESS Tech’s leadership structure, strengthening the balance sheet, and sharpening execution as we enter the Company’s next phase. Over the past several months, we have taken deliberate steps to position the business for discipline, accountability, and long-term value creation. I want to highlight several recent developments that I believe are important as we move toward our upcoming financial reporting and investor engagements. Leadership and Organizational Reset Earlier this year, ESS Tech

ESS Tech, Inc. (NYSE: GWH) (the “Company”), a leading manufacturer of long-duration energy storage systems (LDES) for commercial and utility-scale applications, today announced the closing of the previously announced registered direct offering with institutional investors of approximately $15 million of shares of Common Stock and pre-funded warrants at a price of $1.75 per share of Common Stock, which price was a premium to the closing price on January 28, 2026. The offering consisted of the sale of 8,571,428 shares of Common Stock (or Pre-Funded Warrants). The public offering price per share is $1.75 (or $1.74999 for each Pre-Funded Warrant, which is equal to the public offering price per share of Common Stock sold in the offering minus an exercise price of $0.00001 per Pre-Funded Warrant). The Pre-Funded Warrants are immediately exercisable and may be exercised at any time until exercised in full. Aggregate gross proceeds to the Company were approximately $15 million. The