Proposal Activity up to ~1.2 GWh and Growing following Energy Base Product Launch Exhibit 99.1 ESS Tech, Inc. Announces First Quarter 2025 Financial Results In Contracting for 50 MWh Energy Base Award with Arizona based Utility Energy Warehouse Startup Completed in the Second Quarter for California Irrigation District systems ESS' Made in the USA batteries Well Positioned to Navigate Tariff Volatility ESS Global Fleet Nearing 2.5 GWh of Transacted Energy WILSONVILLE, Ore. – May 15, 2025 – ESS Tech, Inc. ("E ...