I think this is a matter of what is allowed.
Around us, wood stoves are used a lot to get a barn warm.
I have a 80k BTU propane system in my 52 foot barn, not insulated, and it heats it up to 65 in about 30 minutes if it is like 35 outside.
I use it mostly for fixing things in the winter.
You can either get a 500 pound ( note I used pounds ) bottle or use 100 pound bottles and swap one out while the other is filled. Larger units work just as well, but the tank price get nasty.
If you get a used Natural gas unit and you want to convert it, you will need a regulator swap kit and a new set of nozzles. Propane doesn't burn the same as Natural gas, so the jets are smaller.
Units are very easy to install if you are mechanically inclined. Make sure to soap the fittings before you ignite anything.
