I am assuming (which is dangerous) that this relates to electrical energy where the commercial unit of energy is the kilowatt-hour (kWh). The SI unit of energy is the Joule (J).
One kWh is the power of 1,000 watts transferring energy for an hour. We can define power as:
Power = energy transferred / time (unit: Watt or J/s)
Energy transferred = Power x time
Hence one kWh = 1000 (J/s) x 3600 (s) = 3.6MJ (Mega Joules)