The a/c was already installed when we looked at it new. I am glad it was. We have the 38FLSA Pinnacle. It is about 43ft. Your cooling needs may differ based on your size. We are full-timing and have been chasing the sun. So having been to Florida, New Mexico, Arizona and Las Vegas to name a few hot spots, that third a/c really comes into play. I also turn on the front a/c when we travel using the generator. It keeps the unit nice and cool upon arrival. Additionally, my refrigerator is a residential model and needs power. We were also up in Michigan, Ontario and Wisconsin. Beautiful.