A kilowatt/hour is a unit of electricity. It is the multiple of the amount of power (in watts) that you use, multiplied by the time that you use it. For instance, if you have a heater rated at 1000 watts (1 kilowatt) and you have that heater switched on for one hour then you would have used one kilowatt/hour. Likewise a 100 watt (.1 kilowatt) lamp switched on for 10 hours would also be a kilowatt/hour.