If an engine that requires 3kW to run exists... How many units of electricity will it consume in an hour... (1kWhr=1unit). I cannot get my head around this. I am new to this topic and with no one around to help me. This might be very basic to you all but i am just a kid. Sorry about that My solution: It requires 3kJ for 1 sec.... Therefore 3*3600kJ for 1 hour... Hence.. 3kWhrs i.e. 3 units... Is it correct?!