G - S - H - P:
Let me dispel TWO Ground Source Heat Pump myths first:
1. Carbon savings: A GSHP produces HALF AS MUCH carbon as an oil fired heating / cooling system - based on source energy. Natural gas is a little better than oil, still much worse the GSHP. For a very well built house, as GSHP will add 15,000 lbs of carbon to the atmosphere per year, an oil fired heating system, 30,000 lbs.
Winner: GSHP by a mile.
2. Energy efficency - GSHP vs oil:
a. Oil: Delivered - ship, barge, and truck to your house (20% loss), Burner efficency (15% loss), Distribution efficency (10% loss - new sealed and / or insulated ducts / pipes) = 45% loss, 55% efficency, which delivers 55% of the origional energy in the oil actually heating the house.
b. GSHP: Delivered (74% loss in generation and distribution of electricity), leaving 36% of the origional energy in the oil or coal used to generate the electricity to power the heat pump, which is then MULTIPLIED 3 TIMES by any reasonably designed and installed system, which delivers 108% of the origional energy in the oil or coal to heat the house.
Winner: GSHP by a mile.
Onto the meat of the matter:
Using dirt to heat your home - or - giving new meaning to the old saying "Dirt Cheap"
Dirt? A heat source?
That's where the thermal energy is going to come from. The temps in the earth are higher in the winter, lower in the summer, and steadier all the time than air temps. This makes engineering a way to extract and dump heat more efficient.
Heat Pump?
In the summer it's like living in your 'fridge - In the winter, it's like living behind your 'fridge (without the dust bunnies).
Efficiency
Ideally, a heat pump will extract 3 - 4 times as much heat as it consumes in electricity. Some say GSHPs are not as efficient as this claim. Well, you need to design it right, not cut corners, seal and well insulate your house (you should do it anyway), and if adapting existing distribution, doing that right too. See the blog I found for typical GSHP slip ups. Also, many of the studies cited are quite old, based on older systems, and great strides have been made.
Carbon Footprint -
GSHP's do have a smaller carbon footprint. Don't believe me? Then how about believing Canada, Great Britian, Sweden, etc. who are all betting that using GSHP's to reduce their country's carbon footprints per the Kyoto accords.
Published carbon impact for various means of heating are based on PRIMARY or SOURCE fuel use, this accounts for ALL the elec. used in powering up the heat pump. All transmission losses are accounted for. All list GSHP's as the lowest carbon sources of heat - BY FAR!
I've read many a time that power for both pumps used in a GSHP aren't taken into account, I'd bet neither is the pump in a conventional hydronic system. In either instance, the energy use is small compared to heating and cooling energy. Nor have I heard of anyone including the the diesel fuel burned delivering oil, and propane (then dead heading the trucks back to the depots). For that matter, what about the much more energy intensive and ecologically damaging infrastructure necessary to transport fuel vs electricity. Then, finally, I found a study I can cite. Tesla, the car company, not the ghost of Nicolla, researched it, and found that it takes 18% more SOURCE fuel for the refining and transport for gasoline. Think of it this way, MPG in a car SHOULD be reduced by about 20% to give you the true MPG in source fuel. You might think heating oil would take less source fuel to refine, and maybe even deliver, BUT, notice that the cost of heating oil is the same as gasoline, which indicates it's just as "expensive" ie, energy intensive to produce and deliver as gasoline
