Understanding kW and kWh in Battery Storage
Many people don’t understand the difference between kW and kWh, but the distinction matters. These two ratings appear on every battery system and help determine proper sizing. A useful analogy using a car compares kW to engine horsepower and kWh to a fuel tank size or EV driving range. “Kilo” means one thousand, so one kilowatt equals one thousand watts and one kilowatt-hour is 1,000 watts used over an hours time.
Whats a kW
A kW rating measures power, which shows how much electricity a device or battery can deliver at one time. A 1,000-watt microwave needs 1 kW to operate. A battery’s kW rating determines what you can run at the same time during an outage. Batteries also include a surge rating in kW, which handles short bursts of extra power. Surge ratings matter when starting pumps or motors that need higher startup loads.
Whats a kWh
A kWh measures energy used over time. A 100-watt bulb running for ten hours uses 1 kWh. A battery’s kWh rating shows how long it can supply power during an outage. This duration depends on which loads you use and how long they run. Your utility bills also track energy in kWh. Most home battery names use kWh as the main identifier. The Enphase 10C stores 10 kWh. Most systems allow stacking to increase total capacity as needed. Enphase 10C batteries can stack to 80 kWh. Some battery systems also increase power output (kW) as capacity (kWh) grows.