What do you think you using then to use it? If you could answer I wouldnt mind as I am really curious.
18kwh is equal to a constant drain of 750watts. If e.g. you each had your own tv, own games console, and were in your own rooms not together all the time, you still wouldnt be anywhere near it. Maybe lots of long electric shower and hair dryer usage?
My sister has 4 in her household and uses less than me, and I am a light user. She still only has one fridge, one microwave, one cooker.
It is interesting that some think electric usage increases linearly with occupants.