Battery Bank

A battery bank is a group of batteries wired together to store electricity generated by a solar system. Battery banks provide backup power during grid outages and can store excess solar energy for use at night or during peak-rate periods.

Batteries in a bank can be wired in series (to increase voltage), in parallel (to increase capacity), or both. The total capacity of a battery bank is measured in kilowatt-hours (kWh). A typical residential battery bank ranges from 10 to 30 kWh — enough to power essential circuits for 8–24 hours depending on usage. Off-grid systems often require much larger battery banks (40–100+ kWh) since they must provide all power when the sun isn’t shining. Modern residential battery banks use lithium-ion chemistry (LFP or NMC), which offers high energy density, long cycle life, and low maintenance compared to older lead-acid batteries. Popular pre-packaged battery systems like the Tesla Powerwall (13.5 kWh) and Enphase IQ Battery (5 kWh per unit, stackable) have largely replaced custom-built battery banks in grid-tied residential systems, though DIY and off-grid installations still commonly use individual batteries assembled into banks.