If you have a Light bulb that has a rating of 100 watt, it means that the light bulb consumes 100 J per second. kWh is the unit of energy. You can compare this to the volume of water that comes out of the pipe. A 100 watt light bulb when used for an hour will consume 100 Watt-hour of energy which is 0.1 kWh of energy.
