I went on vacation for two weeks last month and unplugged everything except the fridge and one HP Microserver N54L and the apartment averaged a little over 4 kWh per day (~120 per month, ~1440 per year)

However, when we are not on vacation the average is around 10 kWh per day.

Edit: We don't use electricity for heating or cooling (Sydney, Australia) as it's included with the apartment at a flat rate of 10 AUD (6.61 USD) per month