With propane, there is also the problem of the vaporization rate being very low at winter temperatures. I've got a small 2500W (1850W continuous) dual-fuel generator that I had expected to be able to run off of a 20lb propane tank. It didn't work at all when I actually needed it (surprise!), and I ended up just running on gasoline and having to go out to get more. It has since been working fine off of 3 tanks teed together, although I still haven't seen middle of the winter arctic blast temperatures with that set up yet.