It would be easier to get a bigger generator. With such limited use on a camper, I don't think there is much effort to make them more efficient.
Heat pumps are becoming popular and I would go with them next time. Other than the complaint above, I think those that have them like them. Its not a furnace replacement, but they can heat in lieu of the furnace until the temps get too low - which can mean a lot for propane consumption.
Is there a more efficient, lower power consuming 15K but A/C than the Duotherm that comes standard with most 5th wheels?
I would be interested in finding one that can be run on a Yamaha 2400 generator.
............If , you want your A\C too pump the max volume of cold air into your 5'ver , pull all 4 mounting fastners , unhook the 6 wires or so , and slide the A\C unit over too one side exposing the hole in your roof ! Take a roll of foil backed tape the A\C pro's use for all kinds of jobs and Completely seal off all the little cracks that you will find that allow a significant volume of cold air to escape into the ceiling that you weren't aware , OF !!!
............Next , once you reset the unit inspect the seal that partitions the return air from the cold air and SEE how more cold air is being sucked back into the return air pathway because of a leaky seal , that , you probably didn't , know about !!! These are TWO major sources of problems that significantly reduce the cooling efficiency of any A\C unit !!! I'd venture to say atleast 50% or greater of all trailers have a leaky\sloppy installation of the A\C unit on the roof . , jf