Geothermo theory

[yak651]

Going to be building in the next couple of years, just wondering some ball park figures for the geothermal system? If we went this way the trenches would be horizontal instead of vertical, have plenty of room. Approx. sq footage around 2000.
Thanks!

 

[Luremaker]

Speaking of lowering heating costs... the book, SAUNDERS SHREWSBURY HOUSE, by Shurcliff, W. A. was published in 1982 about this 100% solar house built near Boston and designed with no back up heat source. I think the house was about a 2800 sq ft. The house was designed using water and tons rock to store heat.

The house would be close to 24 years old by now and it would be interesting if it is still 100% solar heated. I can find references to it in google only as an out of print book.

 

[Piedmont3]

The difference in the up front cost is quite substantial.
they qouted us $12,800.00 for the highest efficiency electric heat pump and central air conditioning system they sold. The Geothermal unit cost us $20,500.00. The man that installed the system is someone I have known and done business with for about 15 years. /forums/images/graemlins/grin.gif It didn't seem to help with the cost. /forums/images/graemlins/frown.gif

 

[dooleysm]

I wish I knew more about the costs of the one I installed. However, it was installed by the same company that did our plumbing, floor coverings, and sold us some furniture, so I never saw a breakout of the individual prices of everything.

When I hear my parents complaining of two and three hundred dollar gas bills in the winter for a similarly sized house though, and all I have is a $100 electric bill, I know I made the right choice. Cost savings like that will add up very quickly. I've heard that the average household can expect to come out even in 10 years compared to gas heat. That is, the cost of the geothermal unit plus electricity to run it for 10 years is equal to the cost of a gas furnace and traditional A/C plus gas and electricity to run them for 10 years. After 10 years, the geothermal unit is clearly the winner. This doesn't account for the other financial incentives that may be available for each system.

 

[CTyler]

We have 2500 on the main floor and a full basement. We had bids ~28k-32k two years ago. We went with a high efficiancy furnace and heat pump. I figured the Geo would be about a 20 year payback and will probably need a new system by then and what kind of maint during that time???

 

[Charlie_in_TX]

I don't know. It sounds like something of a wash. If it cost $10k more for geo, finaced at 6% for 10 years (the life expectance of the unit), the monthly additional cost is $111.

In my opinion, $10k more is far more than the additional cost the installer incures. The heat exchangers should be within $1k installed. The water lines run under ground should cost no more than installing a syptic system. I had a quote of $3200 to do that a couple years ago.

As to how is works. It is a heat pump first. It 'pumps' heat from the outside to the inside in winter and inside to outside in summer. A component of a heat pump is the heat exchanger (the outside unit that makes all the noise in a air source unit). It is different in a geo and air source heat pump. As the name implies, in a geothermal it is ground source, in an air it is air source.

 

[dooleysm]

The installation was more involved for the geothermal than a septic system. I helped my father-in-law do both. The trench for the geothermal is a very deep trench, 6-8 feet deep, 300 feet long. Then, someone has to crawl down in that trench and install the lines. Ours were affixed to the edges of the trench at different heights, to keep more dirt between them and better disappate the heat.

The geothermal unit itself is a very heavy beast as well. I talked to the guys who broght it in and they told me it was well over 300 pounds.

I am still very happy with my decision to go with geothermal, and I'm of the opinion that it will only look like a smarter decision as the relative cost of heating fuels continue to rise, compared to electricity.

 

[BobRip]

When I built my house I did a little investigation into geothermal. Most of what I learned has been mentioned by others. One item that I have not seen is system life. The geothermal system does not have to work as hard as a standard heat pump since when it is 20 degrees outside the heat source temperature is still at about the same temperature as when it is 60. Consequently the system should last much longer. This was just an article that I read. Can anyone confirm this?

Bob Rip

 

[buckeyefarmer]

I'm trying to do a quick cost benefit analysis, and I can't see geo paying for itself if you have to pay $20K to have it installed.
In 8 yrs my electric has cost $7105, averaged $74 month, with 10 seer ac (used 3-4 months/yr), and oil fired hot water heat. my last yr electric cost is 18% above the average.
My heat cost for last 8 yrs is $6073 averaged $760 yr/ or $63 month. (last yr oil is 25% above the average).
my totol energy cost averages $137 month.
geo claims to use 1/5 the energy, so I'll subtract 4/5 of the oil cost, figuring the 1/5 will be the increased electric usage, so monthly bill is $87. I save $50 per month, so it will take 400 months, or 33 yrs to recoup the $20K cost, 15 yrs to recoup a $10K cost. Energy cost increases (oil and electric) will track about the same., as my history has shown.

 

[dooleysm]

Well, I would think that you'd be more interested in the difference in price between your A/C and oil heat setup and the geotherm system than the total cost of the geotherm system. That's the number you want to reach to recoup your investment.

Also, from what I've heard, the geotherm systems work better on larger houses, 2000 sq. feet and up. By work better, I mean you recoup your investment quicker. It may take 50 years of heating/cooling a small house to realize any benefits of a geothermal system; in which case, a more conventional setup would probably be advised.

Buckeyefarmer, you heating/cooling costs look to be a good bit less than the numbers I was seeing, which leads me to believe you have good, high-efficiency systems or a smaller sq. ft. house, or both. But really, the only numbers I know for certain are the ones on my own current house.