We have a lp generator and I think it is expensive to run. We only get about 8 hours on a tank of propane. The tank size is about 1/2 larger than the ones you use for bbq grills. It does run cleaner and we haven't had a problem with it, but don't use unless necessary because of the cost.
If I had it to do all over again, I would order my class A without any generator and then have it equipped with solar panels. Would carry a small Honda genny when I needed it to top batteries off or on cloudy days. These small Hondas are reliable and extremely quiet.