I'd never heard of this before moving to Montana. Pretty neat idea if you ask me. If it would work in climates like we have here it should work in the rest of the US.

http://en.wikipedia.org/wiki/Geothermal_exchange_heat_pump

The initial cost of installation could be prohibitive, unless you have a buddy with a backhoe.

they have a demo house at NC State they call the solar house that has one of these. It apparently works really well. If you have a delta T, use it!

Everything I've heard about them is good.

i do HVAC work and my company has installed a few of these systems. they work, and they work very efficiently. the initial expenditure is large, but it will pay for itself in a relatively short amount of time with very low utility usage. if i had a house with some land and was starting from square one, i'd be installing a geothermal system. i think in 10-15 years, these will be very popular systems and much more widespread than they are now.

frye

Which type have you seen installed? The ditch type or the deep well type?

Elementary school near me was having some wells bored for a geothermal system when they hit oil-of all things- so they ended up digging some long ditches and going that route.

i've never actually been on the installation, and we subcontract out the actual geothermal grid to someone else. i've done maintenance on the indoor equipment after the installation was complete and the system was running. the last one we did was a well type, though, but we have done both. it depends on the terrain. i believe the well type is the preferred system. someone with bedrock very close to the surface might be SOL on geothermal systems.

these systems are almost always in extreme suburban or rural locations.

frye

Does it only help on the heating side or on the cooling side too?

heating and cooling both. basically, a geothermal system makes the ambient temperature irrelevant. instead of using the outdoor air to transfer heat, the system uses the water from the geothermal grid to dissipate (or extract) heat.

frye

The well type is more expensive to install, and more expensive to repair if a line should ever develop a leak, but it is less likely to reach a balance point with the ground surrounding the lines because the temp. of the earth becomes more stable the deeper you go.
It's kind of an unusual situation that this would happen, it would have to be an exceptionally long or extremely hot/cold season to affect the ground temp. enough to cause problems with a properly installed lateral system. So, if you have the space, I think that's the way to go.
You can also use the system to heat your domestic hot water, making it even more efficient.