Convert Joules to Kilowatt-Hours
Joules to kilowatt-hours is the conversion you need to turn raw energy figures into the unit on your electricity bill. A kilowatt-hour is a large amount of energy, so one joule is only approximately 0.000000278 kilowatt-hours — the kilowatt-hour number comes out very small.
Joules to Kilowatt-hours conversion table
| Joules (J) | Kilowatt-hours (kWh) |
|---|---|
| 1 | 0.000000277778 |
| 2 | 0.000000555556 |
| 3 | 0.000000833333 |
| 5 | 0.00000138889 |
| 10 | 0.00000277778 |
| 20 | 0.00000555556 |
| 50 | 0.0000138889 |
| 100 | 0.0000277778 |
| 500 | 0.000139 |
| 1,000 | 0.000278 |
The formula
To convert joules to kilowatt-hours, multiply the number of joules by 0.0000002777777777777778 (about 2.78 × 10⁻⁷), or divide by 3,600,000:
kilowatt-hours = joules × 0.0000002777777777777778
A worked example
Say you have 3,600,000 joules and want it in kilowatt-hours:
3,600,000 J = 1 kWh
So 3,600,000 joules is exactly 1 kilowatt-hour, since a kilowatt-hour is defined as 3,600,000 joules.
Why it's an approximation
The definition itself is exact — a kilowatt-hour is exactly 3,600,000 joules, because it's one kilowatt (1,000 watts) sustained for one hour (3,600 seconds). What's rounded is the factor for going the other way. Dividing one by 3,600,000 gives 0.000000277777…, with the 7 repeating forever, so the factor 0.0000002777777777777778 is cut off at a practical number of places and the everyday result stays approximate.
When you'll use it
Turning an energy figure in joules into the kilowatt-hours your power company charges for, estimating what a device costs to run, and comparing energy from different sources on the same unit as your electricity bill.
Frequently asked questions
How many joules are in a kilowatt-hour?
Exactly 3,600,000 joules. A kilowatt-hour is one kilowatt (1,000 watts) run for one hour (3,600 seconds), and 1,000 × 3,600 is 3,600,000 joules.
How many kilowatt-hours are in a joule?
Approximately 0.0000002777777777777778 kilowatt-hours. Since a kilowatt-hour is 3,600,000 joules, one joule is 1/3,600,000 of a kilowatt-hour — a repeating decimal, so it's rounded.
Is the joules to kilowatt-hours conversion exact?
No. A kilowatt-hour is exactly 3,600,000 joules, but dividing by that gives a repeating decimal, so the factor 0.0000002777777777777778 is rounded for everyday use.