Sounds about right Groo, most of the information that i have seen for a 5kw output is almost a gallon an hour. This also depends on the engine you have on your generator. As a rule the older style flathead engines are less fuel effient that the newer overhead valve engines, the OHV are usually a little quieter too.

The generator i used is a 4kw lincoln weld and power with an overhead valve briggs engine and it would run the fridge, freezer, couple of lights, fan, TV and water pump for 10 hours on 2 1/2 gallons of gas.