i take back what I said. I did not know that number was realistic. a 32 deg temp was mentioned. I would guess that the system is water, not glycol. this would probably be the heating mode- rtn to ground side. assuming 35, w/ a 10 deg delta, that puts the "from ground" side @ 45. I had thought that the ground source temp was a 55 degree constant. This would put the ground loop at a 10 degree closest approach temperature.(15 deg average approach to ground) kimko, are these numbers close ? I was told that I would need 2- 300 foot wells for 4 tons of refrigeration. at 10$/ft for drilling in rock(where I am), thats $6,000 Is this consistent with your installations? what is the ratio of well footage for a ton? in my case it would have been 150 ft/ton my electric rate is about $0.12/kwh, in NYC a few miles away, its 0.15 When I was building my house, I really wanted to go completely geothermal, but I couldnt justify the payback. I did install a geo feature though. Under the house basement slab insulation I embedded pex tubing in stone dust. In the summer I circulate the water through my radiant floor loops and then down under the house to dump heat. on startup I can get 2 tons of almost free cooling. steady state about 1 ton. the loop temps are like 70/68.