Geothermal is great for regions that don't experience super cold winters. But it's expensive to install and tied to the cost of electricity to run the pumps. If electricity rates get too high, it becomes prohibitive.
For anyone that's on the buzz, heating with firewood is going to be the cheapest. The key is to burn it efficiently in a gassification boiler. Outdoor boilers are inefficient polluters. I'm assuming that most arborists have access to firewood. Not necessarily true that they want to ever see it after work hours though!
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