I have a Honda 3000 watt inverter unit. After Ike, we got by on two tank loads of gas over about a week. The unit has a eco setting that throttles it down when it is not under a load, extending the run time on the gas tank. Got about two days per tank load. I would run it for about 6 hours, then shut if off for 6. Kept out fridge/freezer going and making ice. Used a bucket of ice under a fan to pump cold air to the ceiling. Made primitive AC. Worked well. While my neighbors were trying to sleep while sweating, we were comfortable. I stocked up 5 gas cans before the storm, and only used 3. It is pricey, but you get what you pay for. And I do use it for power tools and to run a fan in my shop. Also it is a good idea to put some fuel stabilizer in the tank to keep the gas from gunking up.
I bought it in 2005 and have gotten a lot of use out of it.
What sized gas tanks?
Thanks.