NEWBIE almost an owner! - air conditioning question

Came back this week from a vacation around Colorado, New Mexico and Utah, where temperatures were in the 90s. At some places we wanted to visit without the dog, we cranked up the generator and turned on the a/c. We just parked away from other people so as not to bother anyone. This was for periods of no longer than an hour. I would much rather spend the money on gas to run the generator, which really does not amount to much, than leave my dog in a hot motorhome and place his life in danger.