With the default inputs (Power 100; Energy 2.4; Hours of use 24; Electricity rate 18.34; Convert Watts to kWh; State U.S. average (18.34¢/kWh)), this calculator returns Energy 2.400 kWh, Watt-hours 2,400 Wh and Average Power 100.0 W.
Every row is computed with this page's own calculator. Change the inputs above to model your own numbers.
| Hours of use | Energy | Cost at This Rate |
|---|---|---|
| 1 hour | 0.100 kWh | $0.02 |
| 4 hours | 0.400 kWh | $0.07 |
| 8 hours | 0.800 kWh | $0.15 |
| 12 hours | 1.200 kWh | $0.22 |
| 24 hours | 2.400 kWh | $0.44 |
| 168 hours | 16.800 kWh | $3.08 |
| 720 hours | 72.000 kWh | $13.20 |
Select the conversion direction, then enter the available power, energy, and operating-time information. For watts to kWh, provide power in watts and hours of use. For kWh to watts, provide energy in kilowatt-hours and the time over which that energy was consumed.
Enter an electricity rate in cents per kWh to estimate the cost of the calculated energy. The state selector can provide a reference rate. The default U.S. average residential price is 18.34 cents per kWh for June 2026.
The results identify energy in kWh and watt-hours, average power in watts, and cost at the entered rate. Utilities bill electricity in kWh, while device labels commonly show watts, which is why this conversion is useful.
One kilowatt-hour equals 1,000 watt-hours. That can represent 1,000 watts for one hour or 100 watts for ten hours. The same energy total can therefore result from different combinations of power and time.
The shipped default selects Watts to kWh and uses Power: 100 watts, Energy: 2.4 kWh, Hours of use: 24, and Electricity rate: 18.34 cents per kWh. The selected state option is U.S. average (18.34¢/kWh).
Multiplying 100 watts by 24 hours gives 2,400 watt-hours. Dividing by 1,000 converts that amount to kilowatt-hours. The displayed conversion results are Energy: 2.400 kWh, Watt-hours: 2,400 Wh, and Average Power: 100.0 W.
Multiplying the energy by the entered electricity price produces Cost at This Rate: $0.44. This cost represents the converted energy only and does not add fixed utility charges, taxes, or fees.
For devices that cycle or vary their demand, nameplate wattage may not represent average power. A measured kWh total over a known number of hours can be converted back into average watts.
Watts and kWh describe different quantities and cannot be converted without a time period. Watts indicate power, while kWh indicate accumulated energy. Cost also depends on the rate entered, and a single energy rate does not represent fixed charges or more complex utility pricing.
To extend a device calculation into daily, monthly, and yearly operating costs, use the Electricity Cost Calculator. To estimate a household statement that includes fixed charges and taxes, use the Electric Bill Calculator.