Turning an energy total into a power figure
A kilowatt-hour is energy already spent; a kilowatt is the rate it was spent at. Divide the energy by the time it covered and you get the average power over that span. It’s the same arithmetic as getting average speed from distance and time.
This is useful for reading a bill or a meter backward: your utility statement gives total kWh over a billing period, a smart plug logs kWh for one device, and dividing by the hours involved tells you the average load.
The kWh to kW formula
Worked example
The calculator’s defaults are 12 kWh used over 4 hours.
The load averaged 3 kW. If it was a single appliance running steadily, 3 kW is also close to its actual draw. If it was a whole house, the 3 kW average hides big swings — near zero overnight, well above 3 kW when the oven and dryer ran together.
Average power from a monthly bill
| Monthly use | Hours in month | Average power |
|---|---|---|
| 300 kWh | 730 | 0.41 kW |
| 600 kWh | 730 | 0.82 kW |
| 900 kWh | 730 | 1.23 kW |
| 1,500 kWh | 730 | 2.05 kW |
A typical home’s round-the-clock average is only one to two kilowatts, even though its peak draw is several times that. The gap between average and peak is exactly what utility demand charges are built to capture.
What this doesn’t give you
The result is an average, not a peak. Loads that cycle — an AC compressor, a well pump, a thermostatically controlled heater — spend part of the time at full power and part at zero, so their instantaneous draw is higher than this figure whenever they’re actually running. For generator sizing or service-capacity questions, you need the peak, which comes from a demand meter or from adding up the largest loads that can run at once, not from a long-run average.
Common mistakes
- Reading the average as a peak. They can differ by 3× or more for a house.
- Mixing minutes and hours. 90 minutes is 1.5 hours.
- Using it to size a generator. Size for peak, not average.
For the reverse, use the kW to kWh calculator. For the watt-scale version, see kWh to watts.