kWh to Watts Calculator
Watts measure power, the rate energy is used right now. Kilowatt-hours measure energy, the total used over time. You cannot convert one to the other without knowing the time, so this calculator asks how long the load runs.
kWh to Watts Calculator
Energy (kWh) and power (W) are linked by time. Convert between them by entering how long the load runs.
Assumes a constant load over the period. Cycling appliances such as refrigerators draw their rated power only part of the time.
Formulas
- kWh to watts: P (W) = E (kWh) × 1,000 ÷ t (hours)
- Watts to kWh: E (kWh) = P (W) × t (hours) ÷ 1,000
Examples
- A device that used 3 kWh over 2 hours drew 3 × 1,000 ÷ 2 = 1,500 W on average.
- A 1,500 W space heater running for 8 hours uses 1,500 × 8 ÷ 1,000 = 12 kWh.
- A 10 W LED bulb left on for 24 hours uses 0.24 kWh.
Why this matters for backup power
Generators and inverters are rated in watts, which tells you how much they can run at once. Batteries and power stations are rated in watt-hours, which tells you how long they can run it. Your utility bill is in kWh. Knowing the difference helps you:
- Size a battery: a 300 W load for 10 hours needs 3 kWh of usable energy. Try the battery runtime calculator.
- Estimate generator fuel: a generator producing 3.75 kW for 10 hours delivers 37.5 kWh. Our fuel consumption calculator turns that into gallons.
- Understand your bill: a home using 900 kWh a month averages about 1,250 W (900 × 1,000 ÷ 720 hours).
kWh to watts conversion table (over 1 hour)
| Energy | Over 1 hour | Over 8 hours | Over 24 hours |
|---|---|---|---|
| 0.5 kWh | 500 W | 62.5 W | 20.8 W |
| 1 kWh | 1,000 W | 125 W | 41.7 W |
| 5 kWh | 5,000 W | 625 W | 208 W |
| 10 kWh | 10,000 W | 1,250 W | 417 W |
| 30 kWh | 30,000 W | 3,750 W | 1,250 W |
Frequently asked questions
Is 1 kWh the same as 1,000 watts?
Only over exactly one hour. 1 kWh is the energy used by a 1,000 W load running for one hour, or a 500 W load for two hours, or a 100 W load for ten hours.
How do I find the average watts from my electric bill?
Divide the kWh on your bill by the hours in the billing period, then multiply by 1,000. For a 30-day bill, divide by 720 hours. Peak demand will be several times higher than the average, so do not size a generator from the average alone.