This discussion has wandered all over the place
I hope the OP has gained some useful insight
His question was how to figure out , how much he would use the generator so he could budget funds , for the run time charges
I own a Honda and use it one hour, has no context to the question
We don't know how many people or where their going, where they will be camping
The best answer is budget excess money for the generator charges
$30 per day, and hope it doesn't come out to that
Better to budget for it and not use it than have to pinch the wallet and travel with no A/C in a hot Rv on 100 degree days