Watts to kWh Calculator
Watts and kWh measure different things: watts is how fast you're using power right now; a kilowatt-hour (kWh) is how much energy you use over time — and it's what your utility bills. The bridge: kWh = watts × hours ÷ 1,000.
4.5 kWh
1500 watts running 3 hours uses about 4.5 kWh of energy.
Runs in your browser — nothing is sent anywhere. Estimates assume nominal voltage and ideal conditions; confirm with a licensed electrician and local code before sizing wire or breakers.
The formula
Multiply the watts by the hours used, then divide by 1,000. kWh = (Watts × Hours) ÷ 1000. A 1,000-watt device for 1 hour = 1 kWh.
Example: A 1,500-watt space heater running 3 hours: 1500 × 3 ÷ 1000 = 4.5 kWh. At 17¢/kWh, that's about 77¢.
Common questions
- What's the difference between watts and kWh?
- Watts is power (the rate), kWh is energy (rate × time). A 100W bulb uses 100 watts while on; left on for 10 hours it uses 1 kWh. Your bill is in kWh.
- How many kWh is 1000 watts?
- 1,000 watts isn't a kWh on its own — it's 1 kW of power. Run it for 1 hour and you've used 1 kWh; for 5 hours, 5 kWh.
- How do I turn kWh into dollars?
- Multiply kWh by your electricity rate. At 17¢/kWh, 4.5 kWh costs about 77¢. Your exact rate is on your bill, or use our cost calculator.
kWh is what shows up on your bill — see what your usage actually costs at your utility's rate.
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