As we get closer to the installation I find myself talking to more and more people about ground source heat pumps and how they work. There is a lot of stuff out there on the web that describes it and it can get rather complicated. I'm reading all I can but I am not to the point where I can explain it succinctly. I found this very high level description from a source in Canada. I am still looking for a good one that will help me explain this all very clearly.
The other question I get is how popular are GSHP systems? According to the wikipedia article on GSHP systems, there were "As of 2004, over a million systems installed worldwide" and "Each year, about 80,000 units are installed in the USA".
Another important question is "how much does it cost?" Sadly, it seems like a lot. Last year, I was faced with estimates of $16,000 to replace my 20-year-old oil-fired systems with a modern boiler and circulating water coil (hydronics). This GSHP system costs more. On the surface it appears to be a lot more but three things help mitigate that cost. One is that 30% of the system cost gets rebated from the federal government at tax time. For the water heater (the Geospring ASHP) the limit of that is $1500, but there is no limit on the rebate for the GSHP system. That brings the total system cost much closer but still well north of the new oil system estimates. The second thing that helps is that we were able to get a $15,000 zero-percent 5-year loan after getting a home energy assessment from mass-save. (They even gave us some cool new CFL light bulbs which achieve their full brightness much more quickly than the bulbs that I purchased a couple of years ago.) Still it'll cost more to install the GSHP. The operating costs are expected to be much lower than my current system and also lower than a modern oil system + conventional A/C. We expect it to cost about $5000 more after full installation. And one must factor in the $15K interest free loan that I can pay out over the next 5 years.
The other issue with the oil-system upgrade (that we chose not to do) was that I'd have to consider getting my old chimney lined to accommodate the higher efficiency of the hypothetical new oil boiler. We had a quote for about $3000 to do that and it involved removing some bricks to get at a jog in the flue. That was not included in the $16000 estimate.
And for me, best of all is no more oil-system maintenance issues.
So what's next?
We expect the drilling to begin this week. After the drilling, they have to install the pipes in to the 2 6-inch holes and fill them with a thermal grout. Then they excavate a trench from the holes to the house and bore holes in the foundation about 4 feet underground so that the pipes can be connected to the heat pump in my basement.
When they get to excavating for the foundation bore holes, because of the location, my installer will have to remove my existing A/C system condensers pumping down the refrigerant and disposing of it responsibly. Then we'll be without A/C for a while until the new system is going. Hopefully it won't be too long given how hot it has been lately...
When the air conditioners are removed from service I will get my electrician to wire the new electrical circuits and the plumber to hook up my Geospring water heater and holding tank. Can't wait!
Today, I flagged the in-ground sprinkler heads with the hope that the drilling rig and excavator can avoid destroying the ones they must traverse to get to the work area. We also had a couple of tree branches trimmed so that the drilling rig can get in to the work area next to my house.
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