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ESS Energy Warehouse Receives Further Safety Certification

UL 9540 demonstrates comprehensive safety of company’s sustainable long-duration energy storage systems

ESS Tech Inc. (“ESS”) (NYSE:GWH), a leading manufacturer of flexible, sustainable and responsible long-duration energy storage systems for commercial and utility-scale applications, today announced that its Energy Warehouse products have been certified to the UL 9540 standard by ETL. UL 9540 is a comprehensive safety standard for grid-connected energy storage systems which affirms the safety of the battery system and its environmental performance. The standard covers stationary energy storage systems for both outdoor and indoor installations.

This comprehensive certification enables customers to expedite permitting and approval processes for new energy storage projects which incorporate ESS systems and further demonstrates the company’s commitment to deploying resilient and sustainable long-duration energy storage systems that are safe for workers, communities and the environment. ETL certification to UL 9540 follows the ETL certification of ESS iron flow battery modules to the UL 1973 standard in March, 2023 and initial UL certification to the UL 9540A standard in 2022.

Recent use cases illustrate the advantages of ESS’ safe and sustainable energy storage technology. In April, ESS announced a partnership with Coldwell Solar to deliver Energy Warehouse systems to microgrid projects which will power California wineries in regions at risk of wildfire. This follows the January announcement of ESS’ selection by Amsterdam Airport Schiphol to provide a battery system that will enable electrification of airside ground operations. The safety profile of ESS technology was a key factor in both selections.

In addition, ESS was selected by the Sacramento Municipal Utility District (SMUD) to deliver up to 2 GWh of energy storage systems in support of the utility’s 2030 Clean Energy Vision. To build a resilient, decarbonized energy system, ESS technology will be deployed across SMUD’s grid. The safety and flexibility of ESS technology make it ideally suited for siting in densely populated areas where improved grid resilience is needed and safety is a top priority.

ESS iron flow technology provides cost-effective long-duration energy storage and is ideal for applications that require up to twelve hours of flexible energy capacity. ESS systems are well-suited for multiple use cases including utility-scale renewable energy installations, remote solar + storage microgrids, solar load-shifting and peak shaving, and other ancillary grid services. ESS technology is safe, sustainable and has a 25-year design life with unlimited cycling and without capacity fade.

About ESS

At ESS (NYSE: GWH), our mission is to accelerate global decarbonization by providing safe, sustainable, long-duration energy storage that powers people, communities and businesses with clean, renewable energy anytime and anywhere it’s needed. As more renewable energy is added to the grid, long- duration energy storage is essential to providing the reliability and resiliency we need when the sun is not shining and the wind is not blowing.

Our technology uses earth-abundant iron, salt and water to deliver environmentally safe solutions capable of providing up to 12 hours of flexible energy capacity for commercial and utility-scale energy storage applications. Established in 2011, ESS Inc. enables project developers, independent power producers, utilities and other large energy users to deploy reliable, sustainable long-duration energy storage solutions. For more information visit

Forward-Looking Statements

This communication contains certain forward-looking statements regarding ESS and its management team’s expectations, hopes, beliefs, or intentions regarding the future. The words “estimate”, “expect”, “will” and similar expressions may identify forward-looking statements, but the absence of these words does not mean that a statement is not forward-looking. Examples of forward-looking statements include, among others, statements regarding the Company’s ability to execute on orders and the Company’s relationships with customers. These forward-looking statements are based on ESS’ current expectations and beliefs concerning future developments. Many factors could cause actual future events to differ materially. 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.


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