What is a kWh to amp-hours calculator?
A kWh to amp-hours calculator converts an amount of stored or consumed energy into the electric charge a battery must supply at a given voltage. A kilowatt-hour (kWh) is a unit of energy, while an amp-hour (Ah) measures charge — the current a battery can deliver multiplied by the time it sustains it. Knowing both the energy and the operating voltage lets you size a battery bank in the units that manufacturers actually print on their cells.
This is especially useful for solar storage, electric vehicles, and off-grid systems, where capacity is quoted in amp-hours but your demand is often measured in kilowatt-hours.
How does it work?
Energy is the product of charge and voltage, so charge is energy divided by voltage. Because one kilowatt-hour equals 1000 watt-hours, multiply the kWh figure by 1000 to get watt-hours, then divide by the voltage:
Here is the charge in amp-hours, is the energy in kilowatt-hours, and is the system voltage in volts.
How to use
- Enter the energy in kilowatt-hours (kWh).
- Enter the voltage of the battery or system in volts (V).
- Read the charge in amp-hours (Ah). The result appears automatically once both fields are filled.
The voltage must be greater than zero, since dividing by a voltage of zero has no physical meaning.
Worked examples
A 1 kWh battery operating at 12 V holds a charge of:
A 2.4 kWh pack at a 240 V system voltage corresponds to:
Notice how raising the voltage for the same energy lowers the amp-hour figure — high-voltage systems carry the same energy with less current, which is why electric vehicles run hundreds of volts rather than 12 V.
Practical notes
Amp-hour ratings describe a battery’s nominal capacity, but usable capacity is usually lower because deep discharge shortens battery life. Many lead-acid systems are sized for only 50% depth of discharge, so you may need roughly double the amp-hours this calculation suggests. Lithium chemistries tolerate deeper discharge and stay closer to their rated figure.
To work in watt-hours instead of kilowatt-hours, the Wh to Ah calculator applies the same idea without the factor of 1000, and the Ah to Wh calculator reverses the conversion. If you want average power rather than charge, the kWh to watts calculator divides energy by run time instead of voltage.