Convert Kilowatt-Hours to Kilojoules
Kilowatt-hours to kilojoules is the conversion you need when the unit on your electricity bill has to meet the kilojoule figures used on food labels and in science. A kilowatt-hour is what you use when 1000 watts run for one hour, and one kilowatt-hour is exactly 3600 kilojoules.
Kilowatt-hours to Kilojoules conversion table
| Kilowatt-hours (kWh) | Kilojoules (kJ) |
|---|---|
| 1 | 3,600 |
| 2 | 7,200 |
| 3 | 10,800 |
| 5 | 18,000 |
| 10 | 36,000 |
| 20 | 72,000 |
| 50 | 180,000 |
| 100 | 360,000 |
| 500 | 1,800,000 |
| 1,000 | 3,600,000 |
The formula
To convert kilowatt-hours to kilojoules, multiply the number of kilowatt-hours by 3600:
kilojoules = kilowatt-hours × 3600
A worked example
Say you used 5 kilowatt-hours and want it in kilojoules:
5 × 3600 = 18,000 kJ
So 5 kilowatt-hours is exactly 18,000 kilojoules.
Why the number is exact
A kilowatt-hour is 1000 watts running for 3600 seconds, which works out to exactly 3,600,000 joules. A kilojoule is exactly 1000 joules, so a kilowatt-hour is 3,600,000 ÷ 1000 — exactly 3600 kilojoules. Every piece is a defined whole number, so the conversion is exact, not rounded.
When you'll use it
Comparing your electricity usage against kilojoule figures on food labels and in science, or lining up an appliance's energy use with datasheets that quote kilojoules instead of kilowatt-hours.
Frequently asked questions
How many kilojoules are in a kilowatt-hour?
Exactly 3600 kilojoules. A kilowatt-hour is 3,600,000 joules, and a kilojoule is 1000 joules, so dividing gives exactly 3600 kilojoules — nothing rounded.
What is a kilowatt-hour, in plain terms?
It's the unit on your electricity bill: the energy used when a 1000-watt load runs for one full hour. A dishwasher cycle or an hour of a small space heater is roughly a kilowatt-hour.
Is the kilowatt-hours to kilojoules conversion exact?
Yes. A kilowatt-hour is exactly 3,600,000 joules and a kilojoule is exactly 1000 joules, so one kilowatt-hour is exactly 3600 kilojoules with nothing rounded away.