We have an 11,000 BTU air conditioner in our 2011 Great West Van Legend and it did the job in 100 degree F. temperatures last fall for us. We have wall and ceiling insulation and the under chassis was sprayed with sound deadener.
We have ordered an Advanced RV Sprinter B extended van and it will be insulated throughout with blue denim insulation (R7) and covered with HushMat rubber and reflective foil on floors, walls and ceiling. We will also get a 15,000 BTU air conditioner. I don't anticipate any problems.
