Seems like you really want the camper and altho asking about the a/c size, you still want the camper. I live year round in FL, much larger fifth wheel and my 13.5 Duo-Therm does not keep up. 87 to 89 inside with a/c and ceiling fan going, most afternoons. OTOH, I had a Pleasure Way, class B and the very small a/c kept up just fine. If you can get a shady spot, it does make a difference. Good luck in your decision. Just for the record, if I really liked the camper and depending on how much summer use, I would try it. Might be a mistake, might be ok.