What is a kWh to watts calculator?
A kWh to watts calculator turns a measured amount of energy and the time over which it was used into an average power figure. A kilowatt-hour (kWh) is a unit of energy — the total electricity consumed — while a watt (W) measures power, the rate at which that energy is delivered. Dividing the energy by the time tells you how many watts the load drew on average during the period.
This is the inverse of finding energy from power and time. If you know your meter recorded a certain number of kilowatt-hours over a known interval, this tool reveals the steady wattage that would account for it.
How does it work?
Power equals energy divided by time. Because one kilowatt-hour is 1000 watt-hours, multiply the kWh figure by 1000 to express it in watt-hours, then divide by the number of hours:
Here is the average power in watts, is the energy in kilowatt-hours, and is the running time in hours.
How to use
- Enter the energy consumed in kilowatt-hours (kWh).
- Enter the time over which it was used, in hours.
- Read the average power in watts. The result appears automatically once both fields are filled.
The time must be greater than zero — energy used over no time has no meaningful power value.
Worked examples
A device that uses 2 kWh over 4 hours draws, on average:
A load that consumes 0.5 kWh in 2 hours:
And a full kilowatt-hour delivered in a single hour corresponds to exactly 1000 W:
Practical notes
This calculation gives an average power. If a device cycles on and off — like a fridge or an air conditioner — the instantaneous wattage will be higher when it runs and zero when it rests, but the average over the whole interval is what this figure represents.
To go the other way and find energy from a known power rating and run time, use the watts to kWh calculator. If you already have the wattage and want to size wiring or a circuit, the watts to amps calculator and the amps to watts calculator convert between power and current at a given voltage.