According to Red Green :

I believe it's called something like geothermal heat pumps. I think it
was in a monthly magazine from a NC utility company I saw an article on
them. Study from some outfit where test systems were installed in various
parts of the country. One was Burlington VT (about 40 min from Canadian
border). Pretty positive results if I recall. Overall design,
installation and ongoing costs I do not know.

Up north of that border, geothermals (and other forms of ground-source)
HPs are becoming quite popular and well known. We had a guy come in
to give our house a full workup and provide an quote for switching our
house over from baseboard electric to geothermal.

IIRC, he quoted us a 5 ton unit (2200 SF two floor house, _almost_ R2000
construction). This geothermal "style" involves drilling a 100' bore
hole per ton (minimum 10' apart), dropping a loop of tubing down each
hole, and backfilling.

There were "combination" and "separate" units. The separate units
were were the air handler and air heat exchange was one place, and
the control box and pumps were in another (close to where the
wells are). The "combo" unit is when it's all in one box. The "separate"
unit was thought to be more effective for us.

As I recall, the full quote (including $3K for ductwork -
we have a very open-concept house, and we were going to be able to
"cheat" a bit and still get proper airflow) was around $18K.

In contrast, a straight forced air gas furnace install (not including
ductwork) would be $7K - there is no gas in this area, though there may
be in another year or two.

The claim was our heating power consumption would decline by about
60%. I worked it out having a break even point of about 10 years. We
decided to wait a few more years and check again - they have us on their
calender to call back, but they're doing so much business now, we may
have to call them ;-)

Do google searches for "geothermal ontario" and you'll find _lots_
of references/descriptions of how it works, installers etc. We get
rebates for installing geothermal now. H'm, the break even just got
a lot shorter ;-)
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.