My uncle has a direct-exchange system- refrigerant in copper pipes directly to the ground, no intermediary water loop. It's about 6 yars old, working like a charm in CT. Along with hydronic radiant on the 2nd floor, he keeps the (3000sqft) house at 75 and hasn't kvetched about electric bills ever! (And he is CHEAP)

There is something too elegant about working WITH the temperature gradient in the summer (and sort of in teh winter too) to pass up! Hopefully next year I'll be adding on to the house, to include a geo system.

With a smaller compressor that is indoors and not even compressing much in the summer and no exposed parts, failure rates should be far lower than with air-source heat pumps. Some get wiggy about hundreds of feet of piping in the ground, but look at everything else that is underground and works fine for decades! IIRC the industry can point to very good track records for 20-25 year lifetimes.

sidebar: To get the $300 federal tax credit (you probably already saw this on the geo site) you need to have a desuperheater, normally used to heat your domestic hot water. Free hot H20, at least in the summer. Makes it a possible tossup with solar hot water- though the solar will still heat the water in winter too, where the heat pump normally won't (or will preheat at best, using extra energy instead of waste energy). So you can make up that $300 in a year or so with soalr H20.

Last I heard the complet greenlight to include geo for the $3K (yes- thousand) federal renewable energy credit was not completed yet. It is implied, and authorized, but not foramlly funded yet. Is this still correct?