I have a cousin who lives up in the Dartmouth area. There is plenty of college and hospital folks who live in the area. I do work where it interests me sometimes. I have spent plenty of time in NH myself, being a snowmobiler. I happen to like the pittsburg area the best. The top of the State just seems to never change, it's like going back in time up there.
As far as geothermal goes, you probably already know the basics of how to do it. Some are wells , and some are just lines buried in the yard 4-5 feet down in a loop or in rows. The best way to learn about it for your area is to talk to one of your HVAC companies already doing it in the area. There are load calculations for temp days that need to be done. Sometimes the cost is also not going to justify installing a system. These systems work well in the top southern areas of the US. Places like Delaware and Kentucky, Ohio. But the further North you go, the more auxillary heat you may end up using. It also depends on how insulated and leaky the home you are working on is. I have seen folks put in a system and not update the homes tightness. They ended up with larger electric bills and did not understand why.
I like geothermal, but I think if folks did more upgrades to their homes, the money is better spent.And... You could heat it with a candle.
I know Glenn has a system, he should be along soon.