The electrical power of an appliance is how much electrical energy it uses in a second. In other words the RATE at which electrical energy is converted to other forms.

In one second a 100W light bulb uses 100 J of electrical energy and converts some of it into light energy.
However in one second an immersion heater may use 3 kW (3000 W) of electrical energy, converting it into heat energy.

Electrical power = VI

[Power is measured in watts, current in amps and voltage in volts].

For large amounts of power we use kilowatts kW (1000 W) and megawatts (1000 000 W). A large power station will operate at over 1000 MW!

Using Ohm’s law (V = IR) we can derive two alternative versions of the power equation: