Just an observation here.
2 weeks ago in 95° temps I was running the rear a/c in our 5er which is 15k btu off my gen using the 20 amp outlet. I had to use a 50ft extension cord and an adapter to the 50 amp power cord because the gen is too heavy to lift out of the truck bed by myself.
The gen ran the a/c with no problem. It did pull down quite a bit at start-up but then ran for 7+ hours until I shut it off. It still had about one gallon of gas left.
Obviously it would best without an extension cord but it worked just fine.