What is a home battery?

A large rechargeable battery stores solar power for nighttime use or keeps essentials running during an outage. It is the missing piece that lets rooftop solar…

A large rechargeable battery stores solar power for nighttime use or keeps essentials running during an outage. It is the missing piece that lets rooftop solar serve a home around the clock.

How to think about sizing one

Batteries carry two numbers that both matter. Capacity, in kilowatt-hours (kWh), is how much energy it holds — how long it runs things. Power, in kilowatts (kW), is how much it can run at once. Most happy owners size for essentials, not the whole house.

How to decide, step by step

1. Pick the job first: shifting solar power into the evening, backup during outages, or both. The answer changes the right size.
2. List what truly must keep running in an outage: fridge, lights, Wi-Fi, medical devices, a well pump. Size to that list.
3. Match the numbers to it — enough kWh for the hours you care about, enough kW to start your biggest load.
4. If you have (or plan) solar, check compatibility: some batteries pair only with certain inverters, and retrofits differ from new installs.
5. Ask a licensed installer about current incentives and your electric rates. Batteries pay back fastest where evening electricity costs most.
6. Agree placement and permits before buying — batteries have fire-code rules about where they can be mounted.