View Full Version : Geothermal - Home Built

Richard Hanley
08-23-2006, 11:30 AM
Dose An One Know Of Any One Making A Home Made Geothermal Home Heating System? Plans - Information? I Would Like One But Think The Prices Are Outrageous. Richard

08-23-2006, 12:40 PM
I don't know much about geothermal energy, but I looked my lab's website and maybe the following link may help you.


and the following article describes some proposals sent to NREL regarding power generation from geothermal sources. Although the scale is much larger than a single home, maybe it will give some ideas.


Good luck,


08-23-2006, 12:52 PM
Dose An One Know Of Any One Making A Home Made Geothermal Home Heating System? Plans - Information? I Would Like One But Think The Prices Are Outrageous. Richard

The equipment price is in line with what a top of the line gas 96%+ furnace would cost. It is the well(s) or loop costs and the price of the special thermal welded plastic pipe. You will need one well (bore hole 200 ft +/- deep) per 12,000 Btu's or 500 to 700 ft of loop for each 12,000 Btu's in this area. Most loopers or drillers in this area (Iowa) are booked about 4-6 weeks in advance. A 200 ft bore hole in this area will run you about $1,500 - 2,000. That price includes the pipe and loop running / welding. The hook up and installation of the equipment is additional cost. Don't forget the duct work. The load sizing is a VERY important part of the job, few fly-by-nighters even know about a Manual J (building) load calcuation and loop sizing, let alone be able to do one.
My suggestion... do what I'm going to do, insulate the house very well and then put in an air source heat pump with a High Eff. gas furnace. Good Luck.

Brian H.
08-23-2006, 01:17 PM

This might give you some ideas:

Read the "history" section.

For convenience, here's the home page link:

I would strongly recommend that you look into a ground source heat pump setup such as this. I understand that you think the cost of the commercial units is excessive, however, it may prove to be cheaper in the long run. The reason I say this is that the heat pump unit itself is not too much more expensive than a regular furnace/air conditioner unit. The main cost of putting in such a system is the installation. You must either dig fairly deep trenches (about 4-6 ft.) or drill vertical wells. If I remember correctly, you need about 200-250 feet of pipe per ton of capacity in a vertical well.

It looks like somebody else beat me to it already... oh well.

You do have a couple of options for laying pipe besides wells; you can put in horizontal loops, which may be slightly more cost-effective but requires a lot of space, or - the easiest and cheapest option - a pond loop, which has, not surprisingly, a loop of pipe in a good-sized pond. It has the added advantage of your pond not freezing in the winter, unless you live someplace really cold.

As I write this, I'm only about 100 ft. from the IGSHPA headquarters, so if anyone wants more information, I'm sure I can find it.


08-23-2006, 01:18 PM
This is an interesting site if you are building. Long read but well worth it.

08-23-2006, 02:52 PM
Is it possible to convert an air-source heat pump to geothermal?

08-23-2006, 04:42 PM
"Is it possible to convert an air-source heat pump to geothermal?"

Yep, I've done it with a small window-type air conditioner. I just cut off the lines going to the "outside" coil, and put in a water-cooled heat exchanger by running about fifteen feet of refrigeration tubing inside some larger copper tubing. I had the AC mounted in the loft of a cottage where the outside of the unit was in an attic space. The water was provided by my deep well, and dumped in a nearby drainage ditch. The small unit didn't use all that much water. It worked fine for the couple years I was living there. Of course, this was way back when you wouldn't be breaking any laws doing that sort of thing.


08-23-2006, 04:45 PM
The first consideration is where do you live? The climate is the main determining factor as to whether it is practical. The next major consideration is the type of soil you have.

08-23-2006, 06:20 PM
North Texas/DFW, on a rocky hillside.

Motodad, that's a very interesting site you posted.
I've been wanting to do just that for many years.
Can't do it at this house though.

08-23-2006, 06:30 PM
As some others have pointed out the geo units are very expensive to install. A typical 3.5 ton geo installed will be $9-10K. A 13 SEER standard unit is under $5K. One will never break even on the additional cost of installation vs electricity used. If the geo ever breaks the savings are further reduced, high price for parts.

Air cooled units can be had up to 20 SEER. They are also so expensive there are precious few sold. Their price is close to a geo unit installed. This is due to multi speed compressor and vfd on the indoor fan. All parts OEM and all high as a cats back to repair.

I just ordered my brother a new 2.5 ton Trane heat pump split system for $1850. We will change it out this weekend. He will save over $4K from a geo system. Thats a lot of electricity with an average bill of $100. In effect, 3.33 years of free electricity.

As far as the home made angle goes this is the paradigm. The only differance would be using water instead of air for heat transfer. The high dollar vfd compressor and indoor fan most likely would not be used. The water must be pumped by something, a pump. That pump will use electricity, just as a fan motor does. The only differance is the effeciency between the two heat transfer mediums. Plus, the effeciency dropps off as the pipes corrode and/or fowl over time.


08-23-2006, 06:38 PM
North Texas on a rocky hillside. I suspect it may not be practical. You certainly have high enough ground temperatures to make it feasible but the second factor comes into play. For ground loop geothermal to be effective you must have soil with good thermal conductivity. Dry rocky soil does not fit that description. The heat transfer is directly dependent on the amount of water in the soil as it is the water that has the real heat storage capacity and the ability to conduct that heat to the geothermal system.

Also, if you have rocky soil installing a system could be very difficult and expensive. Have you ever tried digging any deep ditches on your property?

08-23-2006, 10:25 PM
here is the link for the home power magazine.http://www.homepower.com/
Also don't remember what issue/isssues it was in but when the mother earth news was a real outlander magazine. they did a number of articles on the all types of mass thermal heat storage and geo thermal stuff. If you can find them the black cover whole Earth catalogs (Internet style info before the computer).
Had info on it. the white covered one the last one was sort of suburbaned BS so bad it sucked harder than gravity.:D

08-23-2006, 11:06 PM
For what it is worth, I built a new house and moved into it about Thanksgiving of 1984.

The house had a Friedrich 3-1/2 ton geothermal unit installed at less than $3000 (IIRC) including all the ductwork,registers,thermostat,etc.

The well, which also furnishes potable water for the house, is only 60' deep. The heat pump is supplyed only with uninsulated copper tubing and the discharge when cooling is pea warm and cold when heating.

There are two power meters, one for the house and one for my shop. The house meter runs $160 to $170 pe month while the shop runs about $20. The well pump is in my shop. There are no supplemental heat strips. The house is about 2700 sq.ft. and the heat pump does a wonderful job year around. If it ever quits (22 yrs. now) I will do my best to find another just like it. I live in North Central Florida.

Jim W.

08-24-2006, 01:00 AM
A friend of mine is getting too old to fool with wood heat anymore so he had a geo unit installed .
His place is on a rocky hill top here in Southern BC.
All I know is, he's happy with it and it cost him $12,000 Cnd. I think they had to drill a couple of fairly deep wells.
Too rich for my blood but I'm seeing more and more of these systems being installed around here.

08-24-2006, 01:53 AM
James you make a good point about the systems needed fans and pumps & fans.

A goverment contractor did a house in Idaho with a different form of heating. Since this house was located in the north, the emphasis was focused around heating rather than cooling.

On to the technical part. One large room of the basement was filled with large river stones. Most of the south exterior wall looked like a solar panel. Air was moved through the panels during the day and into the house and into the rock room. Both the house and the rocks were heated during the day light hours. Once dark, the rocks acted as a large heat sink to enable the house to be warmed by sending air back through the rock room.

While it was a neat idea, the person that bought the house was told that the energy needed to move the air was close to that needed to heat the house by convential means. So half the basement was lost without much benifit.

08-24-2006, 01:58 AM
I agree with drof34 about the Friedrich water-source heatpumps. They have a nickle-plated exchanger, which is really important if your water is the least bit acidic.

I had one in the last house I built in SC. It was the smallest unit available (18,000 BTU??), and it was quieter than my refrigerator. We couldn't tell if it was running or not without putting an ear to the return grill. It did well from 1987 until we sold the house in 2004. I made the ducts with 1" fiberglass ductboard, which helped keep things quiet.

We did have a little problem with the water valve going to the unit, but that wasn't supplied by Friedrich. You need a really good "soft-closing" valve if your pipe runs are very long. A TACO zone control valve worked best for us.


08-24-2006, 02:27 AM
I have a friend a few miles down the road that put in a geothermal heat system. He had to put in about 1000 feet of ground loop as a well system wasn't practical because of the depth required. This area has a very deep water table in most places and wells like mine at 350' are common, or deeper. Even then the water temperature is only about 43F which means it doesn't have a lot of heat to give up without freezing it.

My friends system only gives about a 2 to 1 advantage at best and that drops to around unity by the end of winter. It hasn't really been worth it and will not likely pay back. Unfortunately, as I have pointed out in the past, there aren't many viable alternate energy options available here that are worth spending money on. Solar, wind, heat pump, water power, none of these are very practical here. If you want to live off the grid here and not burn diesel then you have to burn a lot of trees. In the winter we get around 3 hours of usable low angle light to charge panels and then only if it is clear. In the middle of winter the sun is down to only 14.5 degrees elevation at noon.

I have heated my house in the past for quite a few years almost entirely by wood burning stove. It takes about ten cords of wood per winter and I have a well insulated house with all double pane windows and insulated doors. We used to have the wood delivered by logging truck sometimes and have it dumped in the yard. Even then it's a lot of work to keep the heat going.

A geothermal system won't work at all on my place because the ground is hard as a rock, impermeable and bone dry. The topsoil is only a few inches thick. I live on top of a hill and the water table is 200 feet down. We also have a lot of rocks. When the glaciers went through here a few years back they dropped a lot of sporadics. Some are sitting on top and some are buried. I have several boulders on my property just sitting there on top that weigh at least several tons. When I was digging years ago to put in the natural gas line to the house I discovered that one edge of the garage is sitting on a rock the size of a volkswagen. Digging anything here is a crap shoot. There is always a good chance of hitting a rock, or a big rock, or a monster rock.

To use wind I would either have to log all of my timber, which isn't going to happen, or the mill would have to be on a 120 foot tower, which isn't going to happen.

I wish I had more options, I would really like to take advantage of alternate energy sources, if we had any.

08-24-2006, 08:45 AM
Evan, I suspect that Als (my ol' buddy)system works as he says but he's about 60 years old and I don't see how he'll ever recoup the 12G he spent on this.

08-24-2006, 11:07 AM
As you suggest, my site is not suitable for much of that sort of stuff.

Can't really do solar as I'm on the North face of the hill, with large oaks all over the house on the North.

Can't do a windmill for all the trees. I guess I could poke one up real high, but that would be expensive. I'm sure the neighbors would be thrilled.

I've got the rocks too. One by the carport is about the size of a buckboard, needs to go to the front yard.

Geothermal heat pump is the best option I have. I don't think the water table is too far down, even allowing for the hill. I guess I could get a pretty good idea by checking the altitude diff between the house and the creek at the bottom of the neighborhood. Is it reasonable to assume the water table is X feet below the local streambeds?

I love this home and the neighborhood, but to build the semi-self-sufficient house of my dreams I need to go elsewhere.

08-24-2006, 11:58 AM
In 1989 i had a "Hydro Heat" installed in a new 3000 Sq Ft house . Cost was 12 k Including duct work ,This unit discharged to a lake at a rate of 8 gal per min.The down side to this is that the unit had to be washed out with muratic acid using a acid pump I have a lot of iron in the water, something not necessary with a closed loop sys.. It also supplied domestic hot water .Heating on a cold night it would lose ground 8 deg F or colder.. It also had a back up electric grid ( per local code ) It supplied air conditiong by means of a large raditor , it worked ok. would lose ground on a hot day.The unit was ok on heating bills as the house was total electric . About 150$ a month . Then trouble started .the compressor burned out after 2-1/2 yrs They covered parts but labor was another 600$They diconnected the domestic hot water heating as the repairman said it was making the unit stop and start too much.( I feel it was never designed right as far as the domsetic hot water heating ) T he second compressor burned out in 1995 . they wanted 1500$ to replace the compressor , By then natural gas had come through the area so i got a gas furnace and central air.
In looking back i would do it over again if i could not get natural gas. I would prefer a closed loop system ( did not have room for it at the time ) I believe the company went out of business mid 1990's . I was told later that the problem was not enough air running over the compressor to cool it. It required 1800 CFM and the blower module only supplied 2000 CFM . So if the media filter plugged up 10 % the compressor was running on the high end as far as temp. went > But yes i would consider it again , my brother in law has one that has been running since 1989 , It is a" Water Furnace"