I have three diesel generators, 5500, 3500 and 3000 watts continious. (they are some of my toys

) The air cooled Chinese copies of Yanmar's and they don't exactly smell like roses

The bigger one, 10 HP, is rated at 9 hours 50% load on 3 gallons. (or 1 gallon per 3 hours) So in your case that would be about 17 gallons

When Ike came through here last August that was about how much fuel I used per hour but I ran it 3 hours on/3 off and that kept the refrigerators cold.
How did you get such good fuel "mileage" out of a gasoline unit or was it a small one when I only got/get 3 hours per gallon on #2 diesel

I had a 7000 watt gas Generac I sold my daughter and son inlaw and it drank gas like a fish during the outage.
Edit. I forgot I have a 1000 watt Kipor inverter smart throttle unit that has ratings close to yours
