Battery Storage Calculator
Estimate the battery capacity needed for a backup load, calculate runtime from an existing battery, or determine how many battery modules are required.
Battery storage example
A 1,000 W average backup load running for 10 hours requires 10 kWh delivered to the loads.
With 5 kWh battery modules, this example rounds up to 3 modules or 15 kWh installed nominal capacity.
What should be included in the backup load?
Use the average power of the loads you expect to run during an outage. Critical loads often include refrigeration, lighting, communications, heating controls, pumps and selected outlets. Large heating, cooling, cooking or motor loads can materially increase both energy and power requirements.
Battery storage FAQ
What is depth of discharge?
Depth of discharge is the share of nominal battery capacity you allow to be used. A 90% usable depth of discharge means 10% is left unused as reserve.
Why include inverter efficiency?
Battery energy is typically converted to AC power before it reaches household loads. That conversion is not perfectly efficient, so usable AC energy is lower than nominal battery energy.
Does this calculator size the inverter?
No. Inverter sizing depends on simultaneous load, motor starting current, surge demand, voltage and system architecture. This calculator focuses on stored energy capacity.