If you want a long term solution you could look into geothermal heat. A ground source heat pump is a significant up front investment but you'll not be relying on fossil fuels once it's up and running and the ongoing cost is minimal.
Oil and gas - including propane - are only going to get more expensive and compound the damage to the planet.If you're planning tostay put it might be worth investing.
Also check out this thread
Added to the idea above of heating a well insulated tank with solar maybe use a wind brake at the same time. Even if you're just raising the temperature a few degrees by these methods it will all add up.