kilowatt hour

kilowatt hour

Unit whose name includes an SI unit and a non-SI unit accepted for use with SI
Name Symbol Quantity Value in SI units
kilowatt hour kW h energy 3.6 MJ
3.6 × 106 J


The kilowatt hour, symbol kW h, is a non-SI derived unit of energy, accepted for use with the SI. One watt is equal to the power required to transfer energy at a constant rate of one joule per second. It follows that, at a constant power of one kilowatt (kW), the amount of energy transferred in one hour (h) is equal to 3.6 megajoules (MJ), or one kilowatt hour (kW h).

The kilowatt hour is derived from the watt (an SI coherent derived unit) and the hour (a non-SI unit accepted for use with the SI).

power × time = energy expressed in SI units
1000 W × 3600 s = 3 600 000 W s 3.6 MJ
1 kW × 1 h = 1 kW h 3.6 MJ

The kilowatt hour is a non-SI unit of energy commonly used in household energy bills.