kilowatt hour
Unit whose name includes an SI unit and a nonSI unit accepted for use with SI
Name  Symbol  Quantity  Value in SI units  
kilowatt hour  kW h  energy  3.6 MJ 3.6 × 10^{6} J 

DefinitionThe kilowatt hour, symbol kW h, is a nonSI 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 nonSI 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 nonSI unit of energy commonly used in household energy bills.