I have a 5000 BTU unit in my 38' it works fine, It is a cruise air brand. I just bought a Honda generator 2000w portable it works great and will do the air too. Its very quiet also, I just set it on the swim platform and connect a line to the power input. I just have to keep the water heater off while running. I think the air installed was about 3500. It was "thrown in" to make the deal go when I bought the boat.