BESS (Battery Energy Storage System)

BESS (Battery Energy Storage System) is a grid-scale battery installation — almost always lithium-ion today — that stores electricity for peak shaving, time-of-use arbitrage, grid services and extended backup power, distinct from the smaller UPS strings inside a data hall. Where a typical UPS module delivers 50-300 kW for 5-15 minutes to bridge the gap to generators, a BESS scales into tens or hundreds of megawatts with hours of duration, and operators increasingly deploy both in a layered architecture: UPS for millisecond ride-through, BESS for longer bridging, peak shaving and utility grid support. The global BESS market is projected to grow from roughly $77B in 2025 to over $170B by 2030 as data center electricity demand climbs toward 945 TWh by 2030, with projects such as Energy Vault's multi-campus B-Nest deployments targeting gigawatt-scale storage tied directly to AI campuses. Pricing is typically quoted in $/kWh installed and varies sharply between ex-works China cells and fully installed Western systems — a distinction our BESS Price Index tracks separately.