kilowatt hour (kWh)
1 kilowatt hour = 3,600,000 joules
What is kilowatt hour?
A kilowatt hour is a unit of energy equal to 1,000 watt hours. It is the standard billing unit used by electricity providers worldwide to measure household and commercial energy consumption.
Notes: Electricity billing
Real-world uses
The kilowatt-hour is the standard unit for electricity billing worldwide. A typical household uses 250–1,000 kWh per month. EV charging, home appliance energy consumption, and solar panel production are all expressed in kWh. Utility bills list total kWh consumed and price per kWh.
History
The kilowatt-hour became the standard billing unit for electricity in the early 20th century as public electricity grids were established. Its use is mandated for utility metering in most countries. It equals exactly 3,600,000 joules (3.6 MJ).
Common mistakes
Writing "kW/h" instead of "kWh"—the slash implies division (kW per hour), which is a rate of power change, not an energy unit. Also confusing kWh with kW: a 2 kW heater running for 4 hours uses 8 kWh of energy, not 8 kW.
When is this conversion used?
Electricity bills use kilowatt-hours while physics calculations use joules. Converting between them is essential for energy audits, comparing appliance efficiency, and understanding power consumption.
How to convert kilowatt hour to joule
To convert kilowatt hour to joule, multiply the value by 3,600,000.
Conversion formula (from base unit)
x * 3.6e6
Measurement standards
The joule is the SI derived unit of energy, defined as one kilogram-metre-squared per second-squared (kg·m²/s²). The kilowatt-hour, equal to exactly 3.6 megajoules, is accepted for use with the SI by the BIPM for practical electricity metering.
Did you know?
A single bolt of lightning releases roughly 1 to 5 gigajoules of energy, yet only a small fraction reaches the ground as electrical current. Most of the energy dissipates as light, heat, and the thunder shockwave.
| kilowatt hours | joules |
|---|---|
| 0.1 | 360,000 |
| 0.5 | 1,800,000 |
| 1 | 3,600,000 |
| 2 | 7,200,000 |
| 5 | 18,000,000 |
| 10 | 36,000,000 |
| 25 | 90,000,000 |
| 50 | 180,000,000 |
| 100 | 360,000,000 |
| 250 | 900,000,000 |
| 500 | 1.800000e+09 |
| 1,000 | 3.600000e+09 |
Common values
| kilowatt hours | joules | |
|---|---|---|
| A food calorie (1 kcal) | 0.00116222 kilowatt hours | 4,184 joules |
| A AA battery | 0.0026 kilowatt hours | 9,360 joules |
| Boiling a kettle | 0.11666667 kilowatt hours | 420,000 joules |
| Daily human diet (2000 kcal) | 2.32444444 kilowatt hours | 8,368,000 joules |
| 1 gallon of gasoline | 36.6 kilowatt hours | 131,760,000 joules |
Full kilowatt hour conversion table
| Unit | Value | Factor |
|---|---|---|
| joule | 1 kWh = 3,600,000 J | × 3,600,000 |
| kilojoule | 1 kWh = 3,600 kJ | × 3,600 |
| calorie (thermochemical) | 1 kWh = 860,420.6500956 cal | × 860,420.6500956 |
| kilocalorie (dietary) | 1 kWh = 860.4206501 kcal | × 860.4206501 |
| watt hour | 1 kWh = 1,000 Wh | × 1,000 |
| megajoule | 1 kWh = 3.6 MJ | × 3.6 |
| electronvolt | 1 kWh = 2.246943e+25 eV | × 2.246943e+25 |
| British thermal unit | 1 kWh = 3,412.14163313 BTU | × 3,412.14163313 |
| therm (US) | 1 kWh = 0.03412956 therm | × 0.03412956 |