Cost to Dig Vertical Well for Geothermal Heat Pump?

[westes]

I'm looking at a geothermal heat pump system for combined heating and cooling for a home under 3000 sq ft. Does anyone have approximate budget numbers to use for the cost to dig either a horizontal or vertical trench for the geothermal heat exchange tubing?

Does anyone know if they ever use copper for the heat exchange tubing? It seems like the efficiency of the heat exchange would be much better for copper than the rubber-like tubing I see on most systems.

[inf_sys]

The cost is going to be based in the local market for well drilling or land excavating. There is not going to be a good ballpark that is going to be valid across the country. Standard geothermal setups use the high-density polyethylene pipe and contains a mixture of water and anti-freeze (propylene glycol, denatured alcohol or methanol). The piping length on average is about 500 ft per ton of system installed. These are two loop type systems where one loop in the refrigerant loop in the cabinet of the unit in the house and this exchanges with the secondary buried loop that is one of several types like closed loop, open loop, vertical or pond coil.

There is a newer type of unit that is hitting the residential market that is geothermal DX (direct exchange). This is a type that uses copper pipe instead as you asked. The piping requirement are on average about 1/3 to 1/2 that of the standard water source unit. The copper is installed in similar fashion and then it transfers heat directly via refrigerant instead of using the water/glycol mixture resulting in EER ratings of 20-30% higher. You could search the web for geothermal dx or http://www.geoexchange.org will probably have more technical information available.

Water source heat pump are great as there is a constant ground temp to work with versus air to air where they is a wide temprature range of operation and conditions. They are great with electric consumption that really are hard to beat even with the highest HSPF air to air on the market today. I would not install one unless I planned on living in the house for a long time to come as the install cost is obviously going to be greater and payback will come with time.

[jerryd_2008]

I'm looking at a geothermal heat pump system for combined heating and cooling for a home under 3000 sq ft. Does anyone have approximate budget numbers to use for the cost to dig either a horizontal or vertical trench for the geothermal heat exchange tubing?

Does anyone know if they ever use copper for the heat exchange tubing? It seems like the efficiency of the heat exchange would be much better for copper than the rubber-like tubing I see on most systems.

Don't think the moderator will like cost numbers given. But I just went through proposals for a replacement HVAC system, including geo and DFHP's. After all rebates, some pretty substantial on the DFHP, and tax credits, the high-end DFHP with VS furnace and 2 stage compressor versus the one geo proposal showed geo to be close to 3 times the cost. For our modest total annual energy costs on a pretty good size house which is probably 700 sqft larger than yours, even with hot water desuperheater, the payback was maybe not in my lifetime. Do the numbers for your usage and life style. Or if you are sold, as I almost was until on did the math, pay the price.

Not sure about copper, but all geo I have seen here uses tubing. May have to do with the life of the in ground infrastructure. Tubing can last 50 years I hear. Copper?????

[jerryd_2008]

...

Water source heat pump are great as there is a constant ground temp to work with versus air to air where they is a wide temprature range of operation and conditions. ...

Not sure of the constant earth temp you state. I too thought that but a geo contractor told me that the ground temp goes up substantially over the course of the summer due to all of the heat you are constantly dumping into the wells. Make sure you discuss that very carefully with reputable contractors in your area so there are no gotchas.

[westes]

Don't think the moderator will like cost numbers given. But I just went through proposals for a replacement HVAC system, including geo and DFHP's. After all rebates, some pretty substantial on the DFHP, and tax credits, the high-end DFHP with VS furnace and 2 stage compressor versus the one geo proposal showed geo to be close to 3 times the cost. For our modest total annual energy costs on a pretty good size house which is probably 700 sqft larger than yours, even with hot water desuperheater, the payback was maybe not in my lifetime. Do the numbers for your usage and life style. Or if you are sold, as I almost was until on did the math, pay the price.

Not sure about copper, but all geo I have seen here uses tubing. May have to do with the life of the in ground infrastructure. Tubing can last 50 years I hear. Copper?????

In theory, a geothermal system should not be that much more expensive to design and manufacture. So I really wonder why the pricing is so bad. I guess the companies specializing in those systems have targeted rich people with large budgets and the mainstream market just has not caught onto the idea yet. It's really a shame that this happens because common sense tells you that in a competitive market the cost for these systems should not be more than 25% above other technologies, and with the proper tax incentives, the systems would become cheaper.

[man from trane]

Where I lived in the midwest, the payback usually occurred immediately prior to the failure of the heat exchanger coil. :(

Also in the midwest, for budgeting purposes we would figure around per ton, but as mentioned, there are too many variables to nail it down.

[beenthere]

Not as big market for Geo's, so the cost will stay higher, until they gain a bigger percentage of the market.

And thats enough about prices.

[man from trane]

Not sure of the constant earth temp you state. I too thought that but a geo contractor told me that the ground temp goes up substantially over the course of the summer due to all of the heat you are constantly dumping into the wells. Make sure you discuss that very carefully with reputable contractors in your area so there are no gotchas.

The ground temp may be constant but the well temp sure isn't. I've seen it go from 38 in the winter to 90 in the summer in the midwest.

[beenthere]

Man from trane.

REREAD site rules, NO prices.

[inf_sys]

Not sure of the constant earth temp you state. I too thought that but a geo contractor told me that the ground temp goes up substantially over the course of the summer due to all of the heat you are constantly dumping into the wells. Make sure you discuss that very carefully with reputable contractors in your area so there are no gotchas.

We are a certified geothermal installer and operation of a water source heat pump will vary with entering water temperature but closed loop systems which are always installed below local calculated frost line the ground remains constant. Usually at least 6 feet. As for well pull and dump which is pulling from a well and cycling backing into the same well remains at a relatively constant temperature. Having a WSHP with an entering water temp of 55 is going to have different ratings from one with a 75 degree entering temp. Always contract with a local geothermal expert with references that can provide the details of operation. The cost of manufacturing of this equipment is a bit more just due to the volume that is sold. They will also be more prevalent is certain areas than others. My only point is that people are very happy with them when they decide to drop the money on a system like this. Running and air to air in PA with a outdoor temperature of 0 is going to affect the units ability to produce heat without use of a lot of resistance heat for backup. All variables need to be looked at as there are many install options for systems of this type. One nice things is that you can have hot water recovery as well that will heat your water when the system is running to assist lowering electrical on a hot water heater.

[westes]

Man from trane.

REREAD site rules, NO prices.

To be fair, I was NOT trying to price EQUIPMENT. I am trying to get a sense of the high and low RANGE of prices for a well or trench.

[westes]

We are a certified geothermal installer and operation of a water source heat pump will vary with entering water temperature but closed loop systems which are always installed below local calculated frost line the ground remains constant. Usually at least 6 feet. As for well pull and dump which is pulling from a well and cycling backing into the same well remains at a relatively constant temperature. Having a WSHP with an entering water temp of 55 is going to have different ratings from one with a 75 degree entering temp. Always contract with a local geothermal expert with references that can provide the details of operation. The cost of manufacturing of this equipment is a bit more just due to the volume that is sold. They will also be more prevalent is certain areas than others. My only point is that people are very happy with them when they decide to drop the money on a system like this. Running and air to air in PA with a outdoor temperature of 0 is going to affect the units ability to produce heat without use of a lot of resistance heat for backup. All variables need to be looked at as there are many install options for systems of this type. One nice things is that you can have hot water recovery as well that will heat your water when the system is running to assist lowering electrical on a hot water heater.

I am all for expertise. Do you have suggestions about how to find qualified geothermal expert? Climate Master and WaterFurnace only have three contractors listed for our entire area.

[inf_sys]

The geothermal heat pump consortium at http://www.geoexchange.org has a great locator for finding a registered installer. It used to be on their home page.

[westes]

Don't think the moderator will like cost numbers given. But I just went through proposals for a replacement HVAC system, including geo and DFHP's. After all rebates, some pretty substantial on the DFHP, and tax credits, the high-end DFHP with VS furnace and 2 stage compressor versus the one geo proposal showed geo to be close to 3 times the cost. For our modest total annual energy costs on a pretty good size house which is probably 700 sqft larger than yours, even with hot water desuperheater, the payback was maybe not in my lifetime. Do the numbers for your usage and life style. Or if you are sold, as I almost was until on did the math, pay the price.

Not sure about copper, but all geo I have seen here uses tubing. May have to do with the life of the in ground infrastructure. Tubing can last 50 years I hear. Copper?????

One factor that I am considering in doing a payback analysis is that with an electrical HVAC system we often turn up the set point to the maximum before temperature is unbearable. We are often turned to 82 F on a heat wave day. That's really not a comfortable environment, but anything higher than this and we are going to pay a fortune on utility bill.

With a geothermal system, you get the cooling almost for free, and the electrical usage is mainly about using pumps and fans, so its relatively cheap. As a result, I anticipate that we would be able to actually turn the set point to 76 or something very comfortable, and still realize significant utility bill savings.

That's a kind of qualitative difference that would make it worth spending up to maybe $6K on an installed system. The reality appears to be that these systems cost much more than that.

[man from trane]

Man from trane.

REREAD site rules, NO prices.

Well, you may as well delete the question then because I don't see how I could be any more vague and still answer it.

[jerryd_2008]

The ground temp may be constant but the well temp sure isn't. I've seen it go from 38 in the winter to 90 in the summer in the midwest.

I was referring to closed loop vertical wells. As I recall he told me the summer temp was in the high 90's. You have to be sure your contractor knows what he's doing in terms of number of wells and depth.

[jerryd_2008]

In theory, a geothermal system should not be that much more expensive to design and manufacture. So I really wonder why the pricing is so bad. ...

You have not factored in the HUGE cost of drilling multiple wells that can be 100's of feet deep. What does it cost in your area to drill a well?;)

[westes]

The geothermal heat pump consortium at http://www.geoexchange.org has a great locator for finding a registered installer. It used to be on their home page.

That web site is a great resource. I found one vendor about 70 miles from us that looks incredible. They obviously specialize just in geothermal.

[westes]

You have not factored in the HUGE cost of drilling multiple wells that can be 100's of feet deep. What does it cost in your area to drill a well?;)

Well I guess we know we'll never get that question answered on this web site. :)

[inf_sys]

You have not factored in the HUGE cost of drilling multiple wells that can be 100's of feet deep. What does it cost in your area to drill a well?;)

The other point you want to talk with your contractor about if you are going to pull from a well is that some municipalities have started requiring two wells, one to pull and one to dump. That will add to the cost as well. Just make sure you cover all the points. It can be a great adventure.

[paul42]

With a geothermal system, you get the cooling almost for free, and the electrical usage is mainly about using pumps and fans, so its relatively cheap. As a result, I anticipate that we would be able to actually turn the set point to 76 or something very comfortable, and still realize significant utility bill savings.



GSHPs are the expensive way to achieve that. I keep my 4,000 sq. ft. house at 74 degrees, 40% humidity using a 14 SEER heat pump. Assuming electricity doubles in price, a GSHP at my house would pay for itself in about 40 years.

[jrbenny]

No pricing discussion are permitted, and that is simply what the OP desires.

thread closed