Energy and power units
Power is energy per time (W = J/s). Utility bills usually charge kWh.
| From | To | Multiply by |
|---|---|---|
| 1 kWh | joules (J) | 3.6e6 |
| 1 kWh | kcal | 860.421 |
| 1 kcal (food Calorie) | kJ | 4.184 |
| 1 BTU | joules (J) | 1055.06 |
| 1 watt (W) | J/s | 1 |
| 1 kilowatt (kW) | watts | 1000 |
| 1 mechanical hp | watts | 745.7 |
| 1 metric ps | watts | 735.5 |
| 100 W bulb × 10 h | kWh | 1 |
Notes
- Food “Calories” on labels are kilocalories (kcal).
- Electrical hp ratings on motors may use slightly different conventions.