Solar Battery Size Calculator
Estimate solar battery-bank capacity from daily energy use, autonomy, reserve, usable depth, system efficiency and battery-module size.
Default project preview
38.3 kWh
Battery modules
8
Purchased nominal
40 kWh
Estimated usable energy
28.8 kWh
Estimated autonomy
2.4 days
Calculator
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Enter the project details and calculate a rounded material estimate.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Usable energy need = daily demand × autonomy days × reserve. Nominal bank = usable need ÷ depth of discharge ÷ system efficiency. Modules round up.
FAQ
Solar Battery Size Calculator questions
Why is nominal battery capacity larger than usable energy?+
Depth-of-discharge limits and conversion losses reduce the energy available to loads.
Does this include poor solar-weather days?+
Only through the autonomy-days input. A full design should use local solar production and seasonal weather data.
Is inverter size based only on daily energy?+
No. Inverters must also handle simultaneous and startup loads, which can be much higher than average demand.