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ENGINEERING TOOL

Solar Battery Size Calculator

Estimate the nominal battery capacity needed for daily energy use, backup days, usable depth of discharge and inverter losses.

Solar Battery Size Calculator

FREE ONLINE TOOL
Formula and assumptions

Nominal battery capacity (kWh) = daily use × autonomy days ÷ (depth of discharge × inverter efficiency).

Energy-planning estimate only; it does not size panels, charge controllers, cables or protection. Include seasonal conditions and manufacturer limits in system design.

5 kWh/day for 2 days at 80% discharge and 90% efficiency requires about 13.89 kWh nominal capacity.

STEP BY STEP

How to use solar battery size calculator

  1. Check the input units and assumptions.
  2. Review the result and example.

IN PRACTICE

Example

For 5 kWh/day, 2 days of autonomy, 80% maximum discharge and 90% inverter efficiency, the estimated nominal battery capacity is 13.89 kWh.

GOOD TO KNOW

What does the solar battery size estimate include?

Required nominal capacity (kWh) = daily use × autonomy days ÷ (maximum discharge fraction × inverter efficiency fraction). This energy estimate does not select panels, controller, wiring or protection equipment.

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