Geotherm vs uber high efficiency gas

14 years ago

I own a 4800 square foot home in eastern Washington. I bought the house about a year ago and it was constructed in 1979. I have NO idea what insulation is in the walls, but it still has non-coated double pane windows that are likely original and decent (18 inches or so) of blown insulation in the ceiling. It has a half basement and an uninsulated 1/2 crawlspace (well, floor of house in that area isn't insulated but walls of crawlspace are along with vapor barrier in good shape)

The house is currently heated by a Lennox CompleteHeat system with 2 zones (2 air handlers, single water heat unit) It actually is fairly cheap to run during heating season with gas bills never exceeding $300/month. It has 2 matching A/C units from the mid 90s with (I assume) middle of the road efficiency.

The CompleteHeat has been in for 7-8 years which is pretty typical lifespan before the welds on the watertank fail, leading to a complete loss of hot water and BOTH zones of heating, so naturally I'm seriously considering early empiric replacement. With the current tax benefit I'm considering ground loop geothermal. I had a top of the line ClimateMaster hardware quote provided. Basically it was 2 6 ton ground loops, 2 5 ton best available ClimateMaster units for about $30k. He also then quoted a water to water geothermal unit with storage tank to provide hot water along with a large hot water type solar panel to add heat to the loop during the winter (another $10k).

I'm debating whether it makes sense

1) to do geotherm at all. I am on a natural gas line (rare as I live in the sticks) so I could easily do a best available natural gas heat plus high efficiency A/C setup, probably for $20k

2) to do the very pricey water to water unit for hot water vs just going HVAC geotherm and then buying a 95+% efficiency gas hot water heater

3) My other idea would be to consider doing natural gas/convention HVAC and then spending the extra $20k on the first phase of a PV system for electricity generation. We get over 220 sunny days here (though our winter sunny days are short from 8am to 4pm)

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Comments (6)

thull
14 years ago
I think the proper comparison is probably air source heat pump vs. ground source. Know nothing of your climate (I'm in the SE), but HP moving heat around is generally going to be more efficient than burning gas to make heat, even at high efficiency. Then the question is whether the increased efficiency of ground source makes sense in terms of payback over the reduced cost of an air source system.
vhehn
14 years ago
geothermal is a great technology but with the price of gas today you will probably never see a payback.
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I'm no expert on this, but that energy usage for pumping seems excessive. Have you looked into a closed loop system? I have no clue where the COP will go in the future, but I'm pretty certain that gas and oil costs will continue to rise - and probably at an accelerating rate. I expect that in a decade GSHPs will beat gas and oil for cost, even if their COP stays the same.
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Hey guys finally got the HVAC plans to our builders AC guy. They ran a j-calc and did cost comparisons for the units we specified. The calc shows that we need 3.88 tons including ventilation air. first, we looked at conventional units. Between 14 and 16 seer, there is a $2200 difference in equipment cost. 14 SEER = $10893 & 16 SEER = $13,100 b/c they buy so many 15 seer trane systems, they get the 15 seer system at the same price as a 14seer. For our home, there is only a $90/year difference in operating cost between 15seer and 16seer. so the payback would be 6.7 years to go from 15 to 16 seer. we would pick the 15 seer unit in this comparisson. Air source heat pump in the same range isn't even worth looking at. it only saves an additional $10/month. Again, not a big jump from 15 seer conventional gas. however, the dealer did mention that we would probably have to install a fresh air system if we go with gas heat -- this is due to foam spray in our attic and the corners of our house. we may need to rethingk a few things if we go with gas. this is where it gets interesting. we looked at geothermal. 1. the dealer sells all types of systems and manufactureres -- geothermal, air source heat pump, conventional ac... carrier, trane, frigidaire, water furnace... etc etc. 2. he assured me that he has hundreds of units in each system type installed in the local area. 3. there are two other geothermal companies in town, so should he and their whole company get hit by a bus tomorrow, there is still knowledgable geothermal service in the area. 4. I was initially interested in a closed loop system, but we do have a potable water well on site. a/c guy swears that in over 20 years he has not had a problem with open loop geothermal units on a potable water well in our area. local water quality is very high compared to other states where they have installed them. also says that the temperature in a closed loop varies b/c ground temp changes. says open loop is his preference due to consistent water temp from ground well. 5. top of the line Envision system from Water Furnace is $21,495 but the tax rebate is $6,449. 6. geothermal costs half as much to operate. operating cost for the three units is as follows... 15 seer unit = $142/month = $1708 per year 16 seer unit = $134/month = $1610 per year Geothermal = $ 61/month = $ 732 per year 7. we then put the units into a 6.5% interest loan scenario VS the monthly savings to calculate the investment payoff. Pay off for geothermal VS 15 seer is 4.1 years. Pay off for geothermal VS 16 seer is 3.8 years. 8. an installation tech showed us the geothermal loop piping. they use an iron to fusion weld the piping to the fittings. makes for a solid and thick joint. 9. hot water biproduct from geothermal can be used for hot water in our home. all comments are welcome. please shoot holes in all of this. thanks again!!!
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I thought you should have a homeowner’s opinion. I would prefer natural gas heat. It’s a warmer heat. The cost of natural gas has gone down tremendously! We used to pay $125/month for year-round service: furnace, water heater, dryer. It went down to $95, then $75, and now $54. We don’t even have insulation in the majority of our walls! And natural gas IS clean. Heating oil is the dirty one. At the end of the winter, walls need to be washed down. Of course it’s not as dirty as my Grandma’s old house; it burned pure coal. Propane is clean, but it is tied into the price per barrel of crude oil; that is highly volatile. (The price, not the oil…well yes it is; it’s burned for heat. But you know what I mean…) Electric heat pump is only efficient down to 30 – 40 degrees. Lower than that requires supplemental heating…maybe even a boost from extra electric resistors. So your cost effectiveness depends on how many days lower than 30 degrees your location receives. With the push for solar and wind energy, they will be making more efficient heat pumps for the colder climates. Where we are building, there is not natural gas. A heat pump may be more efficient now, but we are going with geothermal (this is a heat pump, but Delta values will make it run more efficiently) for the long term. We bought the acre next door so we can run the piping horizontally. My brother-in-law has an HVAC company; he became certified in geothermal when some ICF builders wanted the highest efficiency houses. Once the houses were built, (Mid south), the efficiency study determined that a heat pump would be far more efficient than adding geothermal with its associated costs. They have tiny electric bills for their large houses. Our former builder had geothermal in a totally cement house. Geothermal lends itself easily to in-floor radiant heat. I don’t remember if he had AC; he kept his house pretty warm. But if you want AC also, you’ll need to run ductwork also. We don’t know what our energy costs will be in the future. It is the one cost we won’t have much control over. The Supreme Court has already determined that the cost of cleaning up existing power plants was not taken into consideration by the EPA. Going totally electric and relying mostly on solar or wind power lays too much of a financial burden on the utility companies…who will only transfer its cost to its customers. Dependence on oil puts the power in the Middle East. I think the key is getting an energy efficient envelope of a house; that’s why the heat pumps are more effective with the ICF: higher R value. Spend more money on your windows, doors, insulation and walls. THAT’s where your biggest savings will come from.
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I have a high efficiency modulating furnace (Rheem) put in in 2006. It has worked well, nothing beyond standard maintenance checks It replaced a 30 year old furnace so who knows what the efficiency was there; but my bills dropped so much the gas company came out 3 times to check the meter. Of course, in a colder climate than yours, ruko37. As I recall, getting the right size not only for your square feet but also number of windows, insulation etc is very important to continued high performance of the furnace. I guess your decision (80% vs95%) is rather like when I was trying to decide whether to buy a Versa or a Prius. I did the math--how much I drove, how much gas cost and could cost in the future (I assumed more), the gas mileage of the vehicles, to calculate how much I might save with the Prius; then compared to the price difference of the vehicles. In that scenario, even with gas pushing $4, the Versa was much more cost effective for me. You need to do a similar calculation. If the difference is small, go for the higher efficiency.
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zimzim
14 years ago
while it is true a gas prices today ($3 - $4/therm) may take long to get a payback, lest we forget 2 years ago when prices were pushing $14/therm. One good Hurricane in the Gulf and/or the recession ending and we'll see prices back. Nobody can forecast natural gas prices.

For me it was a no bainer. Between the Energy Company rebate ($2000) and the tax credit I'll be taking (30% with NO cap), the price for my Geo (horizontal closed loop) was comparable to a high efficiency HVAC system
thull
14 years ago
Just FWIW, after vhehn's comment, I did a little looking. I think it's due to there being a lot of hydropower, but electric rates in both Seattle and Spokane tend to be below average. There are online calculators out there to help you figure out which is the less expensive energy source (electric or gas) for your situation. And of course, they're both subject to change due to market forces.
marknmt
14 years ago
Cschmelz, I gather you're in the Spokane area? I'm in Missoula, and I have a Climatemaster Tranquility 27, installed two years ago. It provides heat and air conditioning for our century old stucco bungalo. You might be able to find some of my old posts by searching this forum.

I noted just a couple of things in your post. First off, I thought the price for the basic heat pump installation with ground loops was pretty reasonable for this sort of thing. Second, I wondered why your contractor felt the necessity for adding a solar collector to improve the performance during the winter.

My thought, and I may well be wrong, is that if the ground loop is large enough and deep enough you should have no need to help it with the water-to-water/solar collector, which stirked me as Rube Goldbergish. (Keep It Simple, Stupid). That assumes, of course, that your 10 tons of heating/cooling is sufficient.

As for hot water you may well find that with the desuperheater on at least one of your Climatemasters that you don't need a very large or even efficient water heater.

Again, I may well be wrong, but if that heat pump is properly sized and installed and backs up a conventional 40-50 gallon gas water heater you'll have everything you need.

Of course, if you have three teenagers you'll need all the hot water you can get, and all my guesses are hereby withdrawn.

Caveat: I ain't no engineer or installer, and there are better minds than mind on this forum, but that's my two bits for what it's worth.

Good luck,

Mark
marknmt
14 years ago
Correction:

I wrote that you might search this forum, but I was confusing things. I posted more on the renewewable energy board.

Geotherm vs uber high efficiency gas

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