Had one fitted on a truck when I was driving for a mate. To run a 1000w microwave oven, I still had to run the motor at the same time. Will power a portable TV for hours off the battery, but anything over 200w, you need the motor too. A decent gni will cover 2000w, and only use about 1 ltr of petrol every couple of hours I think.
My point is, an inverter won't do the job alone mate.