Free planning tool
Estimate home battery backup runtime
See how long a battery may run your essential loads during an outage. Enter your usable battery capacity and the total power draw you expect to keep on.
Starting surges from refrigerators, pumps and air conditioners can exceed their average draw. Solar charging during an outage can extend runtime, but this calculator intentionally assumes no recharge.
Plan around essentials first
During an outage, prioritize refrigeration, lighting, communications, medical equipment where applicable, and a few outlets. High-heat appliances, electric water heaters and whole-home air conditioning can drain a battery quickly.
Before buying a system
- List what must run during an outage and estimate its watts.
- Ask about startup surge capacity, not only battery kWh.
- Confirm which circuits the installer will back up.