Power consumption

In electrical engineering, power consumption refers to the electrical energy per unit time, supplied to operate something, such as a home appliance. Power consumption is usually measured in units of watts (W) or kilowatts (kW).
The energy used by equipment is always more than the energy really needed. This is because no equipment is 100% efficient. Power is wasted as heat, vibrations and/or electromagnetic radiation. For example, a light bulb does not only convert electric power into light; it also makes some heat.