My QD6000 (diesel) says 1/2 gallon at 1/4 load...3/4 gallon at 1/2 load and 1.2 gallon wide open. That's why I use portables for long, boondocking events. They run for days on end with just a few gallons of gas.
2018 THOR Chateau 35SF
Two Labs, Bugsie & Blondie
I agree with the 1/2 gallon per hour. My 5500 Onan uses 1/2 gallon running both AC's. I suspect the 4000 will use a little less especially running only 1 AC but if you figure 1/2 gallon you won't be disappointed or surprised.