Greetings!
I use a wick type portable kerosene heater. It requires no power, can also use diesel, and it’s dead simple without much to go wrong with it. Then I sit a heat powered wood stove fan on top of it, to have fan circulated hot air without needing any power. Unlike unvented propane heat, it’s nice dry heat, and a lot safer too.
One of the best things I’ve ever done was ditching propane in favor of kerosene/diesel. Even 100+ year old kerosene heaters, stoves, lanterns, and appliances still work good as new. Older, foolproof, dependable technology you can count on, with no battery/electric power needed.
I just checked the Denver Craigslist and there’s of kerosene heaters available cheap, I also saw an alpaca cook stove too. Once in a while they might need a new wick, but other than that there’s nothing more dependable available anywhere.
Cheers!