How is battery backup time calculated?

Runtime is estimated by dividing usable battery energy by the appliance load. This calculator uses 90% of the selected battery capacity as a simple LiFePO4 starting assumption.

Why does a kettle or microwave reduce battery runtime quickly?

Heating appliances use high power for a short time. They can draw several times more than lights, Wi-Fi and a fridge, so they reduce available runtime and can affect the inverter size required.

Battery backup runtime calculator

Choose a battery size and the appliances you want to keep on. The result is an honest starting estimate, not a promise of runtime.

Free tool

How long will your battery last?

Pick a battery size and what you want to keep running.

Battery size

5.0 kWh

Estimated backup time

12.9 hours

Running about 350 W

Rough estimate at ~90% usable depth. Real runtime depends on the exact appliances and battery. A quote sizes it properly.

Get a battery quote

Actual backup time changes with appliance cycling, battery condition, inverter losses, battery temperature and how much charge is available at the start of an outage. Use the result to shape the conversation, then have the final system designed around your home.

Use the result properly

Keep the list to the circuits that matter in an outage. If a high-power appliance is essential, mention it in the quote request so the inverter and battery are assessed together.

Next step

Compare the batteries in the verified catalogue, then request a quote with your backup priorities included.

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