kWh to Watts Converter (and Watts to kWh)
Enter kilowatt-hours and the time they were used over to get watts, or enter watts and the time to get kWh.
How to convert kWh to watts and watts to kWh
- Under Convert, choose kWh to watts (energy over time) or Watts to kWh (power for a time).
- Enter the Energy (Wh, kWh or MWh) for kWh to watts, or the Power (W, kW or MW) for watts to kWh. The 40 kWh and 7,200 W shown are only examples.
- Enter the Time and pick seconds, minutes, hours or days. The time must be more than zero.
- Read the result rows: average power in W and kW, or energy in kWh and Wh. The steps section shows the conversion with your own numbers.
- Scroll to the table under the result to see the same energy or power for 1, 2, 4, 8, 12 and 24 hours.
The example buttons above the form load three ready-made cases: 40 kWh over 5 hours, a 7.2 kW charger running for 8 hours, and a 10 W bulb on for 100 hours. Copy link stores every input in the page address, so you can reopen or share the same calculation. Copy result copies the result lines, and Print / save as PDF saves the inputs, results, steps and date. Reset returns the form to the starting example. All results are calculated from your inputs alone, with no assumed device data.
How do you convert kWh to watts?
A kilowatt-hour is an amount of energy, and a watt is a rate of using it, so there is no fixed number of watts in a kWh. You divide the energy by the time it is used over. Convert the energy to watt-hours (1 kWh = 1,000 Wh), then divide by the hours: power in watts = energy in Wh ÷ time in hours.
For example, 40 kWh used over 5 hours is 40,000 Wh ÷ 5 h = 8,000 W, which is 8 kW. The same 40 kWh used over 8 hours is 5,000 W. A smaller time means a larger power for the same energy, which is why the table under the result shows several times.
How do you convert watts to kWh?
Multiply the power by the time it runs for, then divide by 1,000 to get kilowatt-hours: energy in kWh = power in W × time in hours ÷ 1,000.
For example, a 7,200 W (7.2 kW) device running for 8 hours uses 7,200 × 8 = 57,600 Wh, which is 57.6 kWh. The U.S. Energy Information Administration gives a smaller case: a 40 W light bulb used for five hours uses 200 Wh, or 0.2 kWh.
How many watts is 1 kWh?
One kWh equals 1,000 watt-hours, or 3.6 megajoules, but it is not a number of watts. If you use 1 kWh in one hour, the average power is 1,000 W. Use it in two hours and the average is 500 W. Use it in 30 minutes and the average is 2,000 W.
What is the difference between kW and kWh?
A kilowatt (kW) is 1,000 watts and measures power at a moment, such as the rating of a heater or an EV charger. A kilowatt-hour (kWh) measures the energy used over time, and it is the unit most electricity bills are based on. A 2 kW heater running for 3 hours uses 6 kWh. To price those kWh, use the kWh cost calculator.
Worked examples
| Input | Result |
|---|---|
| 40 kWh used over 5 h | 8,000 W (8 kW) on average |
| 7200 W running for 5 h | 36 kWh (36,000 Wh) |
| 500 Wh used over 90 min | 333.33 W (0.33333 kW) on average |
Calculated by the tool above with these values.
Frequently asked questions
Is a kWh the same as a watt?
No. A kWh is a unit of energy and a watt is a unit of power. To convert between them you need the time, using energy = power × time.
How many kWh is 1,000 watts?
1,000 watts is 1 kW. Running 1,000 W for one hour uses 1 kWh, for 5 hours uses 5 kWh and for 24 hours uses 24 kWh.
Can I use it for an EV charger?
Yes. Enter the charger power in kW and the charging time to get the kWh delivered, or enter the kWh added and the time to get the average charging power. Real charging power can change during a session, so the answer is an average. For the charging time of a whole battery use the EV charging time calculator.
How do I convert Wh or MWh instead of kWh?
Choose Wh, kWh or MWh in the unit box next to the energy field. The converter changes the unit for you, since 1 kWh = 1,000 Wh and 1 MWh = 1,000 kWh = 1,000,000 Wh.
Does the converter save or upload what I enter?
No. The calculation runs in your browser, nothing is sent anywhere and no account is needed. The inputs only appear in the page address if you copy the link yourself.
Related tools
- kWh cost calculator — Use it to turn kWh into a cost at your own price per kWh.
- EV charging time calculator — Use it to see how long a charger takes to fill a battery.
- EV charging cost calculator — Use it to estimate what a charge costs from your electricity price.
- EV charger load calculator — Use it to check a charger against your home’s electrical load.
- All EV calculators — Use it to browse every calculator on the site.
Sources
- U.S. Energy Information Administration, Measuring electricity: watt, kilowatt, watt-hour and kilowatt-hour definitions; the 40 W bulb example