At this very moment I am sitting at a place, a boatyard, with very old & unreliable power. It is supposedly 30amp. Not!
Assuming your AC unit is OK, the trick is to turn everything 110 that you can off at the circuit breaker.
The easy ones are the fridge & water heater. Leave them on propane. Only turn the waterheater on 15 min before you want a shower. Shut the battery charger off too.
The CG voltage must be very low & the demand very high with the heat. A simple little voltmeter plugged into one of your outlets will tell the story, at least on one leg of power.