# watt hour (Wh)

A watt-hour (Wh) corresponds to a power output of one watt (W) over a period of one hour (h). The unit watt-hour is used for the generation, storage and supply of electrical energy, for example in generators, power plants, energy storagesystems, batteries, photovoltaic systems and many more.

For larger time-related performances, the basic unit watt-hour is provided with prefixes, as kilowatt-hour (kWh), megawatt-hour (MWh) and gigawatt-hour (GWh). Thus, a megawatt-hour (MWh) corresponds to a delivered power of one thousand kilowatts (kW) over a period of one hour, and a gigawatt-hour (GWh) corresponds to a delivered power of one thousand megawatts (MW) over a period of one hour. One kilowatt hour is equivalent to 3.6 mega joules of energy.