kWh

The kilowatt hour is a unit of energy equal to 3.6 megajoules. Energy in watt hours is the multiplication of power in watts and time in hours. For example: If you have a light bulb of 40W that is on during 24 hours, it will consume approximately 1 kWh per day.

The most common use of the unit is when energy is delivered by electric utilities to consumers. In this case electricity use is usually billed in kilowatt hours (kW- h, W h): 1 kW- h = 1000 W- h.