kW to kWh converter
Power (kW) times time gives energy (kWh). Convert either way, and see what it costs at today’s price cap rate.
kW and kWh in one minute
kW is a rate; kWh is an amount. Think of a tap: kilowatts are how fast the water flows, kilowatt-hours are how much ends up in the bath. Appliances are labelled in watts or kilowatts; your bill counts kilowatt-hours.
kWh = kW × hours and kW = kWh ÷ hours. One kW is 1,000 watts.
Everyday examples
Costs at the current price cap rate of 26.32p per kWh (1 October to 31 December 2026):
| Example | Power | Time | Energy | Cost |
|---|---|---|---|---|
| Kettle | 3 kW | 5 minutes | 0.25 kWh | 6.6p |
| Fan heater | 2 kW | 1 hour | 2.00 kWh | 52.6p |
| Electric shower | 9.5 kW | 10 minutes | 1.58 kWh | 41.7p |
| Home EV charger | 7 kW | 3 hours | 21.00 kWh | £5.53 |
| 4 kW solar array at full output | 4 kW | 1 hour | 4.00 kWh | £1.05 |
| LED bulb (8 W) | 8 W | 5 hours | 0.04 kWh | 1.1p |
Want the cost of running a particular appliance over a month or a year? Use the electricity cost calculator. For the units on gas bills, see gas units to kWh, and for the idea behind it all, the kilowatt-hour glossary entry.
Frequently asked questions
What is the difference between kW and kWh?
A kilowatt (kW) measures power: how fast energy is used or produced at a given moment. A kilowatt-hour (kWh) measures energy: the amount used over time. A 1 kW appliance running for one hour uses 1 kWh.
How do I convert kW to kWh?
Multiply kilowatts by the number of hours: kWh = kW × hours. A 2 kW heater running for 3 hours uses 6 kWh.
How do I convert kWh to kW?
Divide the energy by the time: kW = kWh ÷ hours. If a device used 12 kWh over 4 hours, its average power was 3 kW.
How do I convert watts to kWh?
Divide watts by 1,000 to get kW, then multiply by hours. A 100 W TV on for 5 hours uses 0.1 × 5 = 0.5 kWh.
Why do batteries use both kW and kWh?
A battery’s kWh rating is how much energy it stores; its kW rating is how fast it can charge or discharge. A 10 kWh battery rated at 5 kW can run at full power for about 2 hours.
What does kWp mean on solar panels?
Kilowatt-peak (kWp) is a solar array’s output under standard test conditions. Real output is usually lower, so a 4 kWp array rarely produces 4 kW, and its yearly energy (kWh) depends on location, orientation and weather.