What a timely question. Just this week we submitted a proposal for a 10-ton system using 2- 5-ton Nordic EMDX units or 2-EMW, depending on whether the system will be open loop or DX.

I would say your quote does sound high, however, I would not condemn this quote without speaking to your contractor.

HereÂs what I would suggest. YouÂre definitely on the right track with the Nordic EMDX unit for all the reasons you already seem to know. Namely a solid reputation for building high-end products and having everything already built and installed in one ÂboxÂ. Keep in mind that these are large and heavy units to install. Be sure your installers can Âget them inÂ.

Another reason youÂre on to something is that this (DX) unit will require 300-feet of drilling  total (3-100 foot boreholes), à 3-inches, instead of à 6-inches. ThatÂs a difference of 600 feet of drilling - and a lot less debris to deal with!

In our case, because of the drill rig we use, we are able to drill boreholes for DX systems on a 30° off axis angle, in a radial pattern. What this means is that at the surface the borefield resembles the apex of a pyramid and then spreads out the further into the earth it goes. This technique allows us to drill quite close to the envelope we are space-conditioning (taking up very little real estate!) and requires very little trenching. In many cases trenching is done by one person with a pick and shovel, without having to use a mechanical excavator. I would suggest seeing whether this is a possibility for your installation as conventional geothermal (liquid/HDPE) and drilling techniques may otherwise result in your property resembling World War I France at Vimy Ridge before all is completed.

You quote was for 300-ft boreholes per ton. ThatÂs rather a lot by almost any standard. What are your ground conditions like; do you have veins of water flowing through or a high water table (it doesnÂt sound like it)?

Anyway, I hope this helps.

SR

It really seems that when you go to do something environmentally responsible you get bitten. We recently did an install in a 3200 sq ft home using a single 80 gallon Polaris hot water heater and a B&G star rated circulator pump, nice cheap install using Hepex. Sure the transfer plates are pricey however increase efficiency by 20%. As far as the reduction in your carbon footprint, you need to find out how your electricity is generated. These units use beaucoup kilowatts, huge. It could be like buying a Prius, and what it takes to make a battery for one of these.

First, I hope you have checked out this page for the latest incentives:
http://www.dsireusa.org/library/includes/map2.cfm?CurrentPageID=1&State=CA&RE=1&EE=1

I am wondering if there is an alternate system you could install - possibly a conventional heat pump with the highest SEER rating you can get (around 22). Throw in R-60 roof insulation, solar hot water, and an ERV. That should "only" add up to $50K or so. Use the rest of the $130K to cover the main part of your roof with solar panels. Your cost of ownership might actually be lower than the geothermal system you have been quoted. It should be possible to model all of this using the REM/RATE software.

For reference, the typical installed cost for solar hot water in PA is $10,000. (household water only - not pool heat) I have heard quotes of *up to* $40,000 for geothermal.

klaire2001,

First, Yes, I do know about the new rebates, and am really thrilled, because that'll make this technology much more affordable for many.

And, as far as other things, you're right on target (or we are, glad you see things the same way :-). We already are planning:
- solar electric (just installed last week)
- sealed attic with R-40 cloesd foam insulation
- ERV
- solar hot water
... and probably solar pool heat.

And, we now will look into a high-SEER conventional heat pump. The REM/RATE software is a very interesting pointer; too bad it only runs on Windows. ince the goal is to heat/cool hydronic floors, does that affect the type of heat pump we should look at? (yes, we're aware of condensation in the floors, and know how to avoid it).

Thanks to all for the feedback and tips!

Congrats on the photovoltaic installation!

I am really glad you are considering payback on your HVAC systems. REM/RATE requires blower door test results - you will need an energy auditor for that. (also the licensing is through auditors/Hers raters)

I looked up the climate for San Francisco:
heating degree days 3011 (with respect to 65 deg F)
cooling degree days 10 (with respect to 70 deg F)

With the systems you initially described, the ground source heat pump is the *backup system* for 3011 HDD, and the *primary system* for 10 cooling degree days. Not a good value at $38,000 for a backup system.

I think you should size the solar hot water so it will be the primary heat source for the hydronic floors, with heat pump as backup. In the summer, you will have excess hot water. Ask your installer about this - I am not sure if there is a need to "dump" heat during the summer - maybe into the swimming pool or a hot tub?

I have no particular expertise with the hydronic/heat pump combination - just that higher SEER is better!

It looks like your goal is to minimize energy usage - have you had pressure testing done on your duct work? Attic ducts are very common in CA - and a few loose connections or open connections can greatly decrease your forced air system efficiencies.

I am really curious - did you ask the HVAC company for a geothermal quote, or did they suggest the idea to you?

Klaire2001,

I appreciate your looking up the climate and your thoughtful comments. Let me try to address the items, and get another sanity-check:

1. San Francisco isn't actually a good model for our climate; better is San Jose, CA, for which I get (see URL):

   heating degree days 587 (wrt 65 deg F)
   cooling degree days 172 (wrt 70 deg F)

2. When you say the GSHP as the backup for the heating, are you assuming that the solar hot water will be the primary?

3. We would love to dump excess heat into the pool.

4. No, we don't have infiltration / heat loss data, because the house is in the midst of remodeling. We're building it to be tight, with the ERV ductwork in a CONDITIONED (sealed) attic.

5. We asked for the geothermal quote; the technology seems like a sensible one, ... and I've got to say, the $30,000 for solar thermal is even more surprising than $39,000 for geothermal.

Given this quote, we're now considering just getting the hydronic floor and ERV installed and finishing the rest of the remodel w/o the rest of the HVAC. Then, once we're living there, figure out how hot the house actually gets, size the HVAC system, ... and use the actual info to choose one & get it installed before the heating season.

Does that make any sense? It can get miserably hot but we've never had A/C, so I'm sure that, with the improved insulation & tight windows, we can survive this summer w/o the rest of the HVAC.

Thanks again!

Here is a link that might be useful: Climate summary - San Jose, CA

And, no, the HVAC company didn't suggest geothermal. I don't know any in Northern California that does, except Supreme Air, which is just starting to do DX installations.

I personally would prefer DX, however last summer's copper prices made that untenable, and my GC is also skeptical of refrigerant underground in areas of seismic activity. Haven't re-checked what a DX installation would cost this year.