Hello,
I am uncertain which Lake County you reside in or what your local temperatures are on average. Provided you have access to it, which I would be surprised if you did not. LPG(propane in North America) would be the most cost effective (compared with electric) and provide a considerable boost in CO2.
There is an alternative that would save money in the long run but would require planning and a bit of hard work. You can use a rocket stove and a large thermal store. Have a look at this querky fella
HERE. I know a greenhouse grower in the U.K. who uses a rocket stove in his greenhouse with great success.
The concept is relatively simple. You burn wood intensely and the wood gas in a secondary combustion chamber. The exhaust is done in a serpentine pattern to maximise heat transfer to your thermal store. (masonry, used brick, rocks or clay mixed with straw) There is very little smoke coming out at the end of your exhaust do to your secondary combustion chamber.
I am making this sound more complicated than it is. Mount your trusty keyboard and Google rocket stoves. I think you might like it.
Cheers,
Will