Storage
What Is a BESS (Battery Energy Storage System)?
A system that stores electrical energy using batteries for later use. Grid-scale BESS typically uses lithium-ion batteries and helps balance electricity supply and demand, integrate renewable energy, and provide grid services.
A grid-scale BESS is a field of battery containers, inverters, and controls that charges when electricity is cheap or abundant and discharges when it is scarce or expensive. Most US systems use lithium-ion chemistry and are rated by both power (MW — how fast they can discharge) and energy (MWh — how long they can sustain it). A '100 MW / 400 MWh' system can deliver 100 MW for four hours.
Batteries earn revenue several ways: shifting solar energy into the evening, providing frequency regulation and other grid services, and backstopping reliability during extreme weather. They are also among the most contested clean energy facilities at the county level — fire-safety concerns drive local moratoriums and setback rules, which CleanPowerDaily tracks county by county.
Related terms
Part of the CleanPowerDaily Clean Energy Glossary — 12 in-depth explainers and 50 defined terms. Definitions are free to cite with attribution.