I'm only going to bump this thread a couple times. If no one responds in a couple days, I'll let it drop to the bottom of the heap. But I figure with over 1 million installations in the US alone, someone has got to have some first hand experience with these systems. In the meantime, I'll look for online "user groups" or "owner's club" - I guess that's what they would be called.

I visited a house in Ohio that had a geothermal air system. At least 300 feet of pipe went underground (out and back?). It ran all of the time and was cheap...but kept the house at about 65-70 degrees F ... which seemed a bit cool. It would probably be more efficient in summer for cooling.

He had a supplemental stove that burned wood pellets. That kicked up the heat if desired.

Sek - I did a little research into geothermal and there doesn't appear to be any danger of long term problems. Most systems are closed loop so there is no coolant to leak out and cause problems. The coolant is in a closed system just like a car's radiator. Also, the type used is probably similar to refrigerants so if you ever did have a leak, the coolant would just evaporate. Since I have the space, I would probably go with a horizontal loop system. The hole would probably only be 4 to 6 feet deep.

An open system wouldn't be a problem either. My house was built before the town had run water and sewer lines down our street so we had well water. Everyone in the area sucked water out of the ground for years and we never had any problems. With an open geothermal system, any water pumped out would be pumped back in so it wouldn't change the level of the water table anyway.