From California's hybrid solar-storage giants to Arizona's rising influence and Texas' pure-play installations, this is your go-to guide for understanding where the biggest batteries are — and who's behind them. battery energy storage systems with project-level size, duration, inverters, point-of- interconnection, timelines, and more. Find opportunities for new investment, identify new counterparties, and access new information that can be input into models or verify data from other sources. The largest upcoming BESS. The US energy storage market in 2025 is undergoing a monumental transformation, defined by a rapid and massive scale-up in Battery Energy Storage System (BESS) capacity. The primary driver is the urgent need to firm up intermittent renewable energy and guarantee grid reliability.