Long-duration energy storage (LDES)

Long-duration energy storage (LDES) refers to storage technologies built to discharge continuously for roughly 8 to 100+ hours, well beyond the 1-4 hour discharge window that standard lithium-ion BESS systems are optimized for. Where short-duration batteries handle frequency response and peak shaving, LDES targets multi-day firming of intermittent renewables and grid resilience — a growing concern as data center campuses sign gigawatt-scale renewable PPAs and need storage that can bridge multi-hour or multi-day generation gaps rather than a few hours of evening peak. Candidate technologies include iron-air batteries (Form Energy markets a 100-hour discharge system), flow batteries, gravity and pumped-hydro storage, compressed-air storage and thermal storage. The US Department of Energy's Long Duration Storage Shot targets a 90% cost reduction for LDES systems by 2030, aiming for roughly /bin/bash.05 per kWh per cycle, a level that would make multi-day storage competitive with building new gas peaker capacity. LDES remains far more expensive and less commercially proven than lithium-ion BESS today, so most 2026 data center storage deployments still use short-duration systems for backup and demand response.