The kilowatt hour (symbol: kW·h) is a unit for measuring energy. It corresponds to one kilowatt (kW) of power being used over a period of one hour.
The kilowatt hour is commonly used for electrical energy, since it may be easier to understand in a practical context than the proper SI unit for energy, the joule, which is a watt second (W·s). The joule is a comparatively small unit, making numbers quite large.
1 kW·h = 3,600,000 joules.