how to choose what size RV furnace?

[dentedvw]

We would like to get an RV furnace, but how do I know what size we need?
Our bus is 31' long, so imagine about 28 feet long inside.

There are several listed in the Craigslist for our area, one is a 24k btu, another is 16k btu. Which would work well for us? The 16k is much, much cheaper. But it's all for naught if it doesn't heat the bus properly.

[lornaschinske]

I would get the bigger one. I think that is what we have in our 22 ft Class c. It is an old suburban, heats well and fairly good on LP. I have read posts on RV forums where they are energy hogs and the fan will drain a battery down over night. We have used it during the winter in GA, NC and TN (mountains). We also used it a few times in the fall in NM. It quit working so we didn't use it herein TX. We tend to use electric since it is included in our site rental.