How Kilowatt-Hours Convert to Amp-Hours
Kilowatt-hours measure energy, while amp-hours measure electrical charge. Voltage connects these two measurements. Without the voltage, a kilowatt-hour value cannot be converted accurately into amp-hours.
This calculator is useful when comparing battery specifications, estimating battery capacity, sizing backup systems, or converting energy-storage ratings into the amp-hour units commonly used for batteries. For example, a 1.2 kWh battery at 12 volts has a nominal capacity of 100 Ah.
The result is a nominal value. Real-world usable capacity can be lower because batteries are not normally discharged completely, and charging, wiring, inverter, temperature, and age-related losses reduce the energy available to a load.
Use the battery’s nominal voltage, not its maximum charging voltage, unless the specification or engineering calculation specifically requires another voltage value.
How to Calculate Kilowatt-Hours to Amp-Hours
Step One: Convert Kilowatt-Hours to Watt-Hours
Multiply the energy in kilowatt-hours by 1,000 because one kilowatt-hour equals 1,000 watt-hours.
watt-hours = kilowatt-hours × 1,000
Using the calculator’s default values:
1.2 kWh × 1,000 = 1,200 Wh
Step Two: Convert Watt-Hours to Amp-Hours
Divide watt-hours by the system voltage to calculate amp-hours.
amp-hours = watt-hours ÷ voltage
Using the calculated watt-hour value:
1,200 Wh ÷ 12 V = 100 Ah
Combined Formula
The complete conversion can be written as one formula:
amp-hours = (kilowatt-hours × 1,000) ÷ voltage
For the default 1.2 kWh, 12 V example:
(1.2 × 1,000) ÷ 12 = 100 Ah
Estimating Usable Capacity
To estimate usable amp-hours, multiply the nominal result by the usable depth of discharge and system efficiency.
usable amp-hours = nominal amp-hours × usable fraction × efficiency
For example, assuming 80% usable capacity and 90% system efficiency:
100 Ah × 0.80 × 0.90 = 72 Ah