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Calculate the nominal energy of a battery

Enter the battery voltage in volts and the capacity in amp-hours. The calculator finds the nominal energy in Wh or kWh.

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The nominal voltage of the battery. It is printed on the battery.

V

The capacity of the battery in amp-hours. It is printed on the battery.

Ah

A nominal estimate. The usable energy is lower because of losses and discharge limits.

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Worked example
  • Voltage: 12 V
  • Capacity: 100 Ah

Result

Energy

1,200 Wh

Working

  1. E = U × Q
    12 V × 100 Ah = 1,200 Wh

From volts and amp-hours to energy

The capacity of a battery in Ah is not enough on its own to find the energy. The voltage must also be known. The calculator uses both to give a nominal estimate, which can be useful when you compare batteries with different voltages.

Use the stated voltage and capacity of the battery. If one of the two is missing, the nominal energy is unknown. Wh and kWh describe energy, while Ah describes capacity in amp-hours.

The formula for the energy of a battery

The formula is E = U × Q. U is the voltage in volts, and Q is the capacity in amp-hours. When the two are multiplied, the result is in watt-hours.

The energy that can be used in practice is lower because of losses and discharge limits. The result therefore does not on its own tell you how long a particular appliance can run, or how much energy can be delivered to it.

Example with 12 V and 100 Ah

A battery has a voltage of 12 V and a capacity of 100 Ah. The nominal energy is 12 × 100 = 1,200 Wh. To get the result in kWh, divide by 1,000: 1,200 / 1,000 = 1.2 kWh.