- Power: The rate of work done by the electric energy is called power. It is denoted by P.
- The SI unit of power is the watt (W).
- Watt is a small unit that's why kilowatt-hour is used as the unit for electrical energy.
- 1 unit of electric energy: When one-kilowatt load works for 1 hour then the energy consumed is called 1 unit of electricity.
1 Unit of electricity = 1 kWh = 1000 Watt-hour = 3.6 × 106 J
1 Kilo-watt = 1000 Watt
- 1 Watt: The energy consumption rate of 1 joule per second is called 1 watt.
EXPLANATION:
Since 1 hr = 3600 sec
1 kWh = 1000 W-hr = 1000 × 3600 watt sec = 3.6 × 106 J
So option 1 is correct.

