The efficiency of the propane furnace could be as high as 96% for the home unit as compared to the 4% or so for the small 12000 btu rv furnace in my coach for back up dave
The 96% high efficency of a home furnace comes from their fan control-- the blower fan keeps coming on after the thermostat reaches the set room temperature. That way you get (almost) every bit of heat out of the system.
I am a Webasto fan, with roof AC's with heat pumps, and electric heaters as backup. I like the Webasto heat the best as it warms up the interior walls and floor.