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Electrical Engineering Calculators

Battery Capacity Calculator

Battery bank capacity in Ah and kWh for a required runtime, allowing for depth of discharge.

Enter values

Results update as you type.

Result

Battery capacity needed

463 Ah

Energy needed
5.556 kWh
Energy delivered to the load
4.444 kWh
Discharge current
46.3 A
100 Ah batteries required
5

About the Battery Capacity Calculator

Battery bank capacity in Ah and kWh for a required runtime, allowing for depth of discharge.

Also known as: battery bank size, ah calculator, watt hours battery, battery sizing.

How to use this calculator

  1. Enter load power, runtime needed, system voltage, usable depth of discharge and the other fields.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Review the breakdown shown under the main result.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Formula

Ah = load W × hours ÷ efficiency ÷ DoD ÷ system V

Worked example

Using the values pre-filled in the calculator above:

  • Load power = 500 W
  • Runtime needed = 8 hours
  • System voltage = 12 V
  • Usable depth of discharge = 80 %
  • Inverter efficiency = 90 %

the calculator returns:

  • Battery capacity needed: 463 Ah
  • Energy needed: 5.556 kWh
  • Energy delivered to the load: 4.444 kWh
  • Discharge current: 46.3 A