Watts to kWh Calculator — Energy from Power and Hours
CalculatorA watts to kWh calculator multiplies power (W) by usage hours and divides by 1000 to get energy in kilowatt-hours, the unit used for electricity billing.
What is it
A kilowatt-hour is power (kW) multiplied by time, and it is the unit your electricity bill charges for. Appliance power is labeled in watts, so divide by 1000 to get kW and multiply by hours of use. This is a simple calculation based on rated power; appliances with variable draw such as inverter units can differ from measured usage.
How to use
- 1Enter the appliance power in watts.
- 2Enter hours of use per day and the number of days.
- 3Press calculate to see daily and total kWh.
Reference
| Power | Usage | Energy |
|---|---|---|
| 100W | 5 h/day × 30 days | 15 kWh |
| 1,500W | 1 h/day × 30 days | 45 kWh |
| 60W | 24 h/day × 30 days | 43.2 kWh |
Sources & standards
FAQ
How many kWh does a 1,500W appliance use in 8 hours a day for a month?
1500 × 8 × 30 / 1000 = 360 kWh. Inverter appliances often draw less than rated power, so measured usage can be lower.
What is the difference between kW and kWh?
kW is instantaneous power (the rate of doing work), while kWh is energy — power multiplied by time. Electricity bills charge per kWh.
Is watts to kWh input sent to a server?
No. This calculator runs in your browser and does not send input to a server.