Convert power to energy
| Power × Time | Energy |
|---|---|
| 100W × 10h | 1 kWh |
| 1000W × 1h | 1 kWh |
| 1500W × 4h | 6 kWh |
kWh (kilowatt-hours) is the standard unit for measuring electricity consumption. Your utility bill charges per kWh used. To convert watts (power) to kWh (energy), multiply by time and divide by 1000.
kWh = Watts × Hours ÷ 1000. Example: A 1500W heater running for 4 hours uses 1500 × 4 / 1000 = 6 kWh.
Multiply watts by hours, then divide by 1000. Formula: kWh = (Watts × Hours) / 1000. A 500W appliance running 10 hours = 500 × 10 / 1000 = 5 kWh.
1000 watts for 1 hour = exactly 1 kWh. 1000 watts for 8 hours = 8 kWh. 1000 watts for 24 hours = 24 kWh. The "kilo" means 1000, so 1 kW = 1000 W.
Watts is power - the rate of energy use at any instant. kWh is energy - the total amount used over time. A 100W bulb uses 100 watts of power; running it for 10 hours uses 1 kWh of energy.
US average is about $0.12-0.15 per kWh. Rates vary widely by location: $0.08 in Louisiana to $0.30 in Hawaii. Check your utility bill for your exact rate.