The definition
Power (in watts) is the rate at which energy is used. Energy (in joules or kilowatt-hours) is the total amount used over time. A kilowatt-hour is what you get when one kilowatt of power runs for one hour.
1 kWh = 1 kW × 1 h = 3,600,000 J = 3.6 MJ
What 1 kWh actually does
- Runs a modern fridge for about 24 hours
- Powers a 10 W LED bulb for 100 hours
- Boils a kettle (~2 kW) for 30 minutes
- Drives an EV about 4–6 km (2.5–4 miles)
- Costs roughly $0.10–$0.40 depending on region
Convert energy units
kWh ↔ Joule
Kilowatt Hour (kWh)
Joule (J)
Press / to focus
| Unit | 1 kWh equals |
|---|---|
| Joule (J) | 3.60000e+6 |
| Kilojoule (kJ) | 3,600 |
| Calorie (cal) | 860,421 |
| Kilocalorie (kcal) | 860.421 |
| Watt Hour (Wh) | 1,000 |
| Kilowatt Hour (kWh) | 1 |
| BTU (BTU) | 3,412.13 |
| Electron Volt (eV) | 2.24694e+25 |
| Foot-Pound (ft·lb) | 2.65522e+6 |
kW vs kWh
Don't confuse power with energy
kW is a rate (how fast). kWh is a quantity (how much). A 1 kW heater running for 3 hours uses 3 kWh — the same energy as a 3 kW heater running for 1 hour.
Related converters
The tools mentioned in this guide — one tap away.
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