Partnership Begins with Planned 80 MWh California Project and Establishes Framework for Long-term Collaboration

ESS Tech, Inc. (ESS) (NYSE:GWH) ("ESS" or the "company"), a leading provider of non-lithium energy storage solutions, today announced the signing of a Letter of Intent (LOI) with Juniper Energy LLC, a renewable energy development company, for the deployment of 500 MWh or more of sodium-ion battery energy storage systems, representing a major milestone for ESS as it continues to expand its business with innovative, sodium-based battery solutions.

The LOI establishes a framework for a long-term partnership focused on deploying ESS's sodium-ion battery energy storage systems across multiple projects over the coming years. As part of the agreement, the companies plan to collaborate on an initial 10 MW / 80 MWh energy storage project in California, which is expected to utilize ESS's recently announced modular sodium-ion AC solution–Bridge™, along with an ESS Energy Management System (EMS), and is targeted for commercial operation in 2027.

"This agreement with Juniper Energy validates ESS's strategy to expand our technology portfolio and bring sodium-ion energy storage to market," said Drew Buckley, CEO of ESS. "The planned deployment and long-term procurement framework reflect the accelerating customer demand we are seeing for safer, domestically sourced alternatives to conventional lithium-ion batteries."

Subject to successful project execution and future project development, Juniper Energy has expressed its intent to procure 500 MWh or more of ESS battery energy storage systems by 2032.

"Juniper Energy is focused on partnering with companies that can successfully bring innovative energy technologies from development into commercial operation," said Keith McDaniels, Managing Partner of Juniper Energy. "ESS has demonstrated its ability to integrate, deploy, and scale advanced energy storage solutions, giving us confidence in its ability to execute on next-generation sodium-ion technology. We look forward to working together to validate the ESS Bridge energy storage platform and support its broader adoption across future energy storage projects."

ESS believes increasing demand for its domestically sourced, non-lithium energy storage solutions is creating significant opportunities across utility-scale energy storage, AI data centers, commercial and industrial facilities, and critical infrastructure applications.

Unlike conventional lithium-ion systems, ESS's sodium-ion technology utilizes abundant materials and is designed to reduce exposure to geopolitical supply chain risks and Foreign Entity of Concern (FEOC) restrictions while supporting domestic energy infrastructure development.

About ESS Tech, Inc.

ESS (NYSE:GWH) is a leading provider of non-lithium energy storage solutions. ESS was established in 2011 with a mission to accelerate decarbonization safely and sustainably through longer lasting energy storage. Using easy-to-source materials, ESS solutions enable energy security, reliability and resilience. We build flexible storage solutions that allow our customers to meet increasing energy demand without power disruptions and maximize the value potential of excess energy. For more information visit www.essinc.com.

Cautionary Language on Forward-Looking Statements

This communication contains forward-looking statements (including within the meaning of Section 21E of the Securities Exchange Act of 1934, as amended, and Section 27A of the Securities Act of 1933, as amended) concerning the company and other matters that involve substantial risks and uncertainties. These statements may discuss the management team’s goals, beliefs, hopes, intentions and expectations as to future plans, trends, events, results of operations and financial condition, or otherwise, based on current beliefs of the management of the company, as well as assumptions made by, and information currently available to, the company’s management. These forward-looking statements can be identified by the use of forward-looking terminology, including the words "anticipate," "believe," "continue," "could," "estimate," "expect," "intends," "may," "might," "plan," "possible," "potential," "predict," "project," "should," "will," "would," or, in each case, their negative or other variations or comparable terminology may identify forward-looking statements, but the absence of these words does not mean that a statement is not forward-looking. These forward-looking statements, which are subject to risks, uncertainties and assumptions about us, may include our anticipated growth strategies and anticipated trends in our business. Examples of forward-looking statements include, among others, ESS’ plans for its business, ESS’ potential opportunities that may exceed 500MWh with Juniper Energy for sodium-ion product, the timeline for ESS’ development of the Bridge product, domestic supply chain availability, statements by ESS’ CEO, and ESS’ ability to grow and our ability to meet the growing demand for energy storage. These forward-looking statements are based on ESS’ current expectations and beliefs concerning future developments and their potential effects on ESS. Many factors could cause actual future events to differ materially from the forward-looking statements in this communication. There can be no assurance that the future developments affecting ESS will be those that we have anticipated. These forward-looking statements involve a number of risks, uncertainties (some of which are beyond ESS control) or other assumptions that may cause actual results or performance to be materially different from those expressed or implied by these forward-looking statements, which include, but are not limited to, our relationship with our customers, including Juniper Energy, and our ability to execute definitive agreements and deliver thereunder, the successful performance of pilot projects, the demand for our Bridge product or BESS projects not developing as anticipated; our ability to realize and capitalize on sodium-ion opportunities; delays in the development of the Bridge product; our products being in the early stage of commercialization and aspects of our technology not having been fully field tested; our inability to develop our business and effectively commercialize our energy storage products; our dependence on third-party suppliers; our ability to secure or maintain long-term supply relationships with critical suppliers; our ability to secure or maintain a domestic supply chain; our ability to secure binding orders; and our ability to raise capital in the near future and other risks and uncertainties described more fully in Exhibit 99.2 of the Current Report on Form 8-K filed by the Company on June 23, 2026 and the Company’s other filings with the U.S. Securities and Exchange Commission. Except as required by law, ESS is not undertaking any obligation to update or revise any forward-looking statements whether as a result of new information, future events or otherwise.

About Juniper Energy

Juniper Energy is a California-based renewable energy developer focused on building the next generation of sustainable infrastructure. With a mission to deploy safe, reliable, and domestically sourced energy assets, Juniper specializes in utility-scale projects that leverage cutting-edge non-lithium technologies to meet the evolving needs of the modern grid.

View source version on businesswire.com: https://www.businesswire.com/news/home/20260722491522/en/

Company

investors@essinc.com

Investor Relations

Chris Tyson

Executive Vice President

MZ Group - MZ North America

Phone: (949) 491-8235

GWH@mzgroup.us

www.mzgroup.us

Media

Brad Dore

VP, Marketing

ESS, Inc.

brad.dore@essinc.com

916-207-7355