If you subtract the cost of a conventional system with its repairs from the geothermal cost, you end up with a cost for a geo system of about $23,000 not including replacement costs of the 10-year old A/C system and the 30% tax credit.

A savings of only 47.6% sounds VERY conservative to me, especially with a desuperheater for the DHW.

Maintenance cost for a closed loop geo system should be about zero other than the cost of air filters. The geo system should also have a much longer life cycle.

CanÂt tell you how to spend your money thoughÂ

What type of hydronic baseboard heaters do you have, aluminum fin or cast iron?

SR

fsq4cw, thanks for your response. I think we mostly have aluminum fin baseboard heaters (except in the dining room, which seems to be cast iron). As to calculating the savings -- it requires so much speculation! And the geothermal contractor won't share their calculations with me. I know how the house performs now (I had a full energy audit conducted this winter, and have analyzed my bills over 5 years), but can't be sure how it will perform once it is insulated, sealed, and added on to....

What type of geo are you planning to install, forced air, hydronic or a combination of the two?

SR

Please pardon my ignorance -- it is definitely a forced air system (too expensive to go with radiant in-floor), but it would also supply our hot water (or at least pre-heat the water? I'm afraid I don't really understand this part, but the quote includes a 50 gallon electric h*t water heater, and we would keep our existing electric h*t water heater as well). Does this mean it is a combination? The quote is for a 4 ton Hydron #HO50, if that helps.

What the 2-hot water tanks mean is that the geothermal desuperheater will produce hot water at about 110°F that will be stored in a passive buffer tank and will feed an active electric hot water tank. This should result in an energy savings of at least 33% with regard to producing hot water. This is not a Âcombination unit that would provide both forced air heating & cooling and full capacity hot water production for in-floor radiant heating. All geothermal units should be available with a desuperheater option for the production of domestic hot water.

During the summer time when youÂre air-conditioning, much the heat thatÂs being extracted from your home will go into your hot water tank as opposed to being vented into the outside air as is the case with a conventional air-conditioner or heat pump. In the A/C mode with a geo system your hot water is considered essentially free.

What type of ground heat exchanger (ground loop system) is being proposed?

SR

A horizontal closed loop system.

I'd be surprised if a horizontal loop only saved 50% compared to propane for heating. Of course it depends on your electric rate and your propane cost but I'd expect your savings to be in the 60-70% range assumming average propane costs and $.10 a kwh.

Converted my oil boiler baseboard/elec AC unit to geo with wells and a desuper 3 years ago here in CT. Also replaced boiler with high efficiency tankless propane water heater for winter's DHW (summer DHW comes free via the geo's desuper). I hooked the geo's "emergency heat" circuit to the tankless DHW heater (no elec coils!) to fire up and circulate hot water to the pre-existing baseboard hot water units. Works great. Geo has held the house to 70F when it was -15F outside and the the "emergency" didn't even come on! Conversion factor for geo wells was 100ft of well for each ton of AC. Total electric bills for my 3000sqft average $2000/yr and I fill my 250gal propane tank 1/yr to run the tankless water heater and my propane high efficiency fireplace insert.

Re: Tom Brown

Sounds like you installed an EarthLinked or some other DX system.

SR