I have a woodstove as main source, but also put in a direct vent forced air 45K propane shop furnace from princess auto for back up, quick initial cabin heat up and the times I am plain too lazy to get more wood. The propane comes via 100lb tank that I fill at Costco for $45 and will give around 50 hours burn time(in a well insulated cabin that is quite a bit for intermittent use), the electricity to run the fan comes from a modest solar panel(90 watts) battery setup. The 16x32 1 1/2 story cabin is used on weekends pretty much year round. That 100 lb tank will last me most of the winter with intermittent use. If I used propane as primary heat 100lbs might only last 20-25 days during an average winter.
As far as cost, I think princess sells this furnace around 500-600 clams during heating season but often marks them down at the end. I got mine for $350 including the horizontal or vertical install 3 inch double wall b-vent kit, spent a couple more hundred on a thermostat,two stage regulator, black pipe and misc wiring stuff. I did the install myself, it was reasonably easy. It comes with detailed general approved code instructions. Probably most important part is leak check you pipe connections, otherwise it's hard to screw up. Total install including wiring, regulator,20 feet of black pipe and out the wall horizontal vent took maybe the better part of a Saturday. I also optionally installed a cold air intake as this furnace is not sealed combustion and will use your inside air for combustion. As such a CO detector is not a bad idea.
As far as performance , for the size of cabin we are taking about that has reasonable insulation the 45000 input btus of this furnace(actual output btu is 36000 at rated 81% efficiency) is more than enough and will give a 10 degree rise in 15-20 minutes. Way faster than the woodstove. I love it for cold arrivals. I normally crank up both the wood stove and furnace when I arrive in a severly cold soaked cabin and can take my jacket off in 20-30 minutes and then let the woodstove take over from there. Now if it was only the wood stove it would take a 1-2 hours to just start feeling warm. I also don't have to worry about waking in the middle of the night to stoke the woodstove as the thermostat will automatically call for heat as appropriate. I personally don't care about getting a little cold overnight but the spouse sure does.
Northerntool also sells this furnace check out their predominantly positive customer reviews. They also sell a non electrice direct vent wall mounted furnace that heats by convection but again you loose out on the quick temp rises without a fan to move the hot air around.
