That is pretty good for a house of that size Mlou. What my customers use varies, some use an exceptionally low amount and others I wonder if they are selling it on the side...
As I mentioned above the condition of the house is a big factor. Installing new windows if you don't already have them can greatly reduce fuel consumption. Most consumers will cut their consumption by 30% with new windows.
The unit itself can be an important factor, new units are very efficient compared to old ones. Another customer I had cut his bill in half by installing a new unit and he mentioned that it was much warmer in the house as well.
Again if you follow that link I provided above and know what you used last year that will give you a pretty good idea of what you will need and the costs.