WatsonJ, if you buy a quality slid in camper, one that has a decent amount of insulation, you will not need a 13,000 or 13,500 BTU A/C, a unit putting out 11,000 BTU's or less, will be plenty. With the smaller unit, a Honda 2000 watt generator will work just fine. A 13,500 unit is the same size that they put in small travel trailers and fifth wheel rigs that have much more volume to cool. I have traveled in a camper that had am 11,000 BTU A/C and a portable generator, it was a Yamaha 2000 watt unit, not a Honda ,and the generator worked well and handled the A/C without a problem and believe me, we were in South Texas and New Mexico in the summer, plenty hot and humid, and after about 30 or 40 minutes, we turned the A/C down to mid range, as it was getting a little uncomfortable in the camper, it was in the mid 90's outside and the mid 70's in the camper.