A battery energy storage system (BESS) is a stationary installation of batteries, inverters and controls that stores electricity and releases it when it is needed.
At grid scale, BESS shifts solar power from midday into the evening peak and steadies the grid. At the scale of a building or a parking facility, it does the same job locally: charging when power is cheap or plentiful and discharging when demand, price or an outage makes stored energy more valuable.
A garage with fast chargers draws a spiky load. The utility bills the highest fifteen minutes of the month. Turn the battery on and set how hard it works.
Without a battery, three fast chargers running at once set a peak near 500 kW, and the demand charge is billed on that peak all month. A 250 kW, 200 kWh battery can hold grid draw near 250 kW by discharging during the spikes and recharging in quiet hours.
Illustrative: 150 kW chargers, 250 kW / 200 kWh battery, $20 per kW-month demand charge. Real tariffs vary.
How parking facilities use BESS
- Peak shaving for EV charging. A battery can supply the surge from DC fast chargers so the site avoids high demand charges and, in some cases, a costly utility service upgrade.
- Pairing with solar. Energy from a solar canopy can be stored for evening charging or building loads.
- Resilience. With the right controls, a BESS can keep critical loads, chargers or a microgrid running during an outage.
Safety and codes
- Stationary energy storage installations are addressed by NFPA 855 and the fire code adopted locally, and equipment is commonly listed to UL 9540.
- Location, separation, ventilation and fire department access are reviewed early; placement in or near an enclosed garage gets particular scrutiny.
The Parkonomics view
For many garages the expensive part of EV charging is not the charger but the electrical service behind it. A battery can make the economics work by buying time and capacity from the grid on the owner’s schedule. Run the numbers on demand charges and service upgrades before sizing chargers; the battery may be the cheaper path to the same number of charged cars.
Related terms: Demand Charge, DC Fast Charging, Solar Canopy, Microgrid, Vehicle-to-Grid
Further reading: EV Charging Did Not Break the Grid. Batteries Fixed It.