School Me on Geothermal

[cdd1]

In the next few months, will start a homebuilding project.

House is located in Philadelphia area, will be a 2 story house, about 4K square feet, full basement and almost a 2.5 (is 20' x 27') car garage.

We'll also have a medium size inground pool (gunite).

I'm wondering if we should consider geothermal. Questions I have are:

• Is the 30% tax credit limited in any way? Income caps, etc.?
• What would a ballpark cost of installation be--incremental to standard forced air/AC.
• I assume that geothermal can supply some of the heat to both the house and the pool
• Recommendations from the knowledge base here on if it's worth the extra expense

We plan to stay in this house for a long time, so I expect to be around to recapture cost savings from the install

Thanks in advance for your thoughts/guidance!

 

[rsanter]

The biggest cost of the geothermal is the excavation for the in ground tubes.
I have seen people save money by doing the trenching themselves because they have the equipment, not sure if that's an option for you. And then the contractor takes it from there.

Geothermal has lost some of its advantage as more efficient air exchange units have come out as we as they have gotten the air exchange units working better when they are in heating mode and it's very cold outside.

For large scale (commercial systems) the cost between the units can be very little. For residential the cost difference is generally more.
Only way to know for sure is to price it out.

We did a test here at my work. We tested the efficiency of the water exchange system versus the direct exchange system. The water exchange system was more efficient

Bob

 

[Justanoldguy]

I've never figured out this "School Me" thing.
Must be American.

Show me or teach is what I know..

 

[yeldogt]

You have to price out the differences .. the cost of drilling the wells is always unknown.

The coast of air units keeps dropping vs goe
With ever higher electric and ever cheaper gas .. the world is changing.
A geo pool heat pump working off 55 degree water is not going to be as efficient as air at 80.

Most people forget that geo units require more maintenance.. cost more and have additional pumps that are often not accounted for.

 

[Jackfre]

Back in the late 70's when I was in the business we used to take a glazed solar array and use it to heat the pool. The pool needed a good insulated cover. We then used the pool water to drive the water source heat pump. Summer you rejected heat to the pool. At worst you needed a small cooling tower.

For the cost OD conventional geothermal (wells or ground tubes) the numbers just don't make sense to me when you can do a mini-split system. In my home here in The Sierra foothills my biggest bill for lights, well, cooling/heating with my mini-splits has been $85 in the hottest and coldest months. I also run a Rinnai Energysaver on lp, but that is efficient too. The mini-splits are tickling the efficiencies of the geothermal

 

[kd3pc]

tax credit? talk to your accountant/CPA

The Geo WILL be more expensive, likely two or three times the cost of conventional systems. It will require more space in the basement/house for equipment. Design will cost more, especially if you are trying to heat the pool...that water is a HUGE heat sink, that just spills heat off.

I have done several houses, 3-4K sq feet, in VA with GEO systems. All were substantially more than conventional systems, but all homeowners were VERY happy with the quality of the air systems, the reliability and the immediate savings they had in heating/cooling large homes. Payback times will depend on prevailing electric rates, fuel oil costs, etc and how hot or cold you keep the home. My dad's 4K sq ft house super insulated brick rambler is less than $40/monthly year round. His system is coming up on 13 years old. He has had to replace a circulation pump and one poorly made plastic water manifold (we use them to enable/disable zones) since installation. Winchester VA, but no rebates/credits were available then, to offset his costs.

 

[mygarageone]

The biggest unknown is what elec rates will be down the road , if the government has it's , way elec rates. Could double or even triple . That makes gas very attractive .
I have never been sold on the geo units, yes there's cost savings in elec over fossil fuels but long term , they will never be better than Nat gas for cost of maintance long term.
Hell , I just yanked out a geo unit for a electric power company employee.
He put in a Nat gas unti and said he's never been happier.

 

[theoldwizard1]

The biggest cost of the geothermal is the excavation for the in ground tubes.

I thought most installation drilled wells ? That seems simpler to me. I guess it depends on you location.

For large scale (commercial systems) the cost between the units can be very little.

One of the Carolinas requires all new public buildings to have geothermal.

For residential the cost difference is generally more. Only way to know for sure is to price it out.

Better get a couple of quotes and check references.

A geo pool heat pump working off 55 degree water is not going to be as efficient as air at 80.

He wants to HEAT the water in the pool, not use the pool as a heat source. Although that is quite common.
Pools are a simple/cheap source of cool water. Heating your pool when the ambient temp is in the 80s does not seem logical, but it is. The pool gives up a lot of heat to the ground and to the air at night, More plumbing for sure.

Remember, A HEAT PUMP DOES NOT MAKE HEAT. IT MOVE HEAT FROM ONE PLACE TO ANOTHER. If you want to heat your pool, you have to make something else cold. You probably don't want to cool the house when the ambient temperature is below 70F so early/late season pool heating is difficult. If that is what you want. make sure it is in the quote.

I have done several houses, 3-4K sq feet, in VA with GEO systems. All were substantially more than conventional systems, but all homeowners were VERY happy with the quality of the air systems, the reliability and the immediate savings they had in heating/cooling large homes. Payback times will depend on prevailing electric rates, fuel oil costs, etc and how hot or cold you keep the home. My dad's 4K sq ft house super insulated brick rambler is less than $40/monthly year round. His system is coming up on 13 years old. He has had to replace a circulation pump and one poorly made plastic water manifold (we use them to enable/disable zones) since installation.

Excellent write up ! While YMMV, this a stake in the ground.

Geothermal heat pump systems pay back fastest in ares that do NOT have natural gas OR have a long cooling season.

 

[Jackfre]

What we did was use the pool as the heat sink for the heat pump. You only need, as I recall from the late 70's, 50* water to work the refrigerant cycle. I do not know how that would work with today's refrigerants, but I cannot imagine it is worse. A 20x40 x average 4' is 3200 cu ft. 7.48 gal/cuft. That can represent a lot of energy.

I guess the question is, would you rather have a pool or a few wells. These systems worked very well. YMMV....as usual!

 

[tgb]

A house of that size and in your area would require multiple units. I have done pool heating in Iowa probably similar climate to you with geo and works well with a water to water unit. I advise you to go with air to air heat pumps for the house and an air to water unit for the pool, geo just costs too much and I have not put in any brands in the last 20 years that were reliable enough to justify the costs. The quick paybacks are often times wiped out by large repair bills around year 5 to 7 and the units have a realistic lifespan of 10 years if a geo runs longer than that its a bonus.

 

[theoldwizard1]

For the cost OD conventional geothermal (wells or ground tubes) the numbers just don't make sense to me when you can do a mini-split system. In my home here in The Sierra foothills my biggest bill for lights, well, cooling/heating with my mini-splits has been $85 in the hottest and coldest months. ... The mini-splits are tickling the efficiency of the geothermal

For a 4,000 sq ft house plus 2.5 car garage. you are going to need at least 2 maybe 3 mini-splits and each would have to be multi-zone. Still, these could be cheaper than geothermal. Zoned this way, they would be very inexpensive to operate. Make certain to purchase one that can operate efficiently at temperature below freezing.

Any home with a heat pump, should really have some kind of some kind of "backup" heat source for extended power outages. Either a large generator that can run a heat pump ($$$$) or 1 (or more) LP/Natural Gas fire places. If you are going to have LP or NG, I would also use them for cooking, heating domestic water and drying clothes.

 

[volleyball]

The thing with geo is the dealer you are working with. That is the most important factor in picking a system.
A water to air system is most common in the NE.
New systems are far more reliable than even 10 years ago. There are even systems designed with heat vs cooling for the northern climates.
The furnaces are about the size of gas or oil furnaces. The ducting will be the same.
The idea of using the pool part of the year to heat the pool with heat removed from the house heat in summer seems like a great idea. Some extra tubing, some valves and your AC cost will not be much more than running some fans.
Being a new house, if you have the room, you can go with the coil loops. Then grade the ground above it, sort of a two for one.
The mini splits or air to air heat pumps are a joke in Pa. Your backup heater will be running a lot, a lot.
Properly sized, well insulated house, not trying to keep it at 75, you will be able to run the system strictly off of the geo pump. I am north of you and I haven't installed the backup coil in my geo and it easily keeps it at 68.
I have deep wells, which I think is a better but costlier upfront cost. But I did not have the space in a mature landscape to put in coils.

 

[theoldwizard1]

Thinking out loud ...

I wonder how big of a swimming pool would be required to be the exclusive heat source for a water sourced heat pump system ?

Obviously this depends on many factors

• volume of the pool
• area exposed to the atmosphere
• area exposed to the earth
• average outside temperature range
• size of the home to be heated/cooles
• insulation in the home
• ???? who knows what else

 

[volleyball]

Thinking out loud ...

I wonder how big of a swimming pool would be required to be the exclusive heat source for a water sourced heat pump system ?

Obviously this depends on many factors

• volume of the pool
• area exposed to the atmosphere
• area exposed to the earth
• average outside temperature range
• size of the home to be heated/cooles
• insulation in the home
• ???? who knows what else

A version of this has been used for decades, look it up.
What the OP has isn't enough.

 

[yeldogt]

Direct Geo pool heaters are less efficient that air -- the air is hotter??


I have seen super heaters on Geo units that take the bleed the heat ... but normally this is more practical for domestic hot water

Pools require a lot of BTU's normally more than HVAC units can provide

 

[theoldwizard1]

A version of this has been used for decades, look it up.

A Google search for "using swimming pool geothermal" turns up mostly solutions for heating swimming pool independent of residential heating/cooling.

EDIT: Using a swimming pool as a geothermal heat source is used mostly in southern areas and typically in conjunction with another heat source (vertical or horizontal loop systems).

A big issue, especially outside of southern areas, is the period of time when both the residence and the pool require heat or possibly cooling. A system could be designed to do this, but it would be quite complex.

What the OP has isn't enough.

Isn't enough WHAT ???

 

[billspit]

I've never figured out this "School Me" thing.
Must be American.

Show me or teach is what I know..

A long time ago someone explained to me as "we speak the Queen's English, not the King's English". Seems it had something to do with Sir Walter Raleigh being friendly with the Queen.

 

[mygarageone]

Here's something to think about , for a while everyone was on the goe band wagon.
That's not the case anymore , out of all the H.V.A.C contractors I know of up here , 20 in my area along. 1 does geo and he has been staying away from it , do to the enormous cost and maintance issues after install.
There is no way you can justify the high up front cost to savings in utilitie cost.

 

[volleyball]

It is easy to justify it in many applications. Just like 99% HVAC guys will tell you off the cuff that oil or gas system retrofit will save you money. I know for a fact that is not the truth for a fairly large number.
The biggest hurdle to geo is the upfront investment. Lots of people just don't stay put long enough to pay it off. While any buyer would love to have it, buyers pay for granite and hardwood floors, not anything that make the place better to live in.

 

[kd3pc]

Here's something to think about , for a while everyone was on the goe band wagon.
That's not the case anymore , out of all the H.V.A.C contractors I know of up here , 20 in my area along. 1 does geo and he has been staying away from it , do to the enormous cost and maintance issues after install.
There is no way you can justify the high up front cost to savings in utilitie cost.

If the geo system is properly designed and installed using decent parts and skills, they are great systems, with little maintenance. Much fewer moving parts.

The biggest reason most HVAC contractors do not sell them, is that they can not be sold in 5 minutes and installed in a couple of hours. With 30% margins. Nor can the contractor stock a couple of sizes, models and units, like they do with conventional HVAC.

Geo requires a design specific to the installation, to be properly sized and to be correctly installed. No shortcuts, almost close, retrofit the existing furnace, etc.

 

[Rock knocker]

If the geo system is properly designed and installed using decent parts and skills, they are great systems, with little maintenance. Much fewer moving parts.

Huh? Instead of a single fan, they have a entire pump and fluid system. You math seems suspect.

 

[volleyball]

Any water system has a pump(s) and fluid system.
A geo air system is basically a commercial AC system. Pretty much old tech. Reliable tech. Doesn't need the cleaning a fuel burning system will require.

But there are differences and you have to learn them. Probably wasn't much around when the HVAC guy was an apprentice learning their craft.
As a teen, with a basic understanding of electricity, and a few tools, I was able to diagnose and repair vehicles that stumped many a 20 year or more master mechanic.
Nowadays a two year tech knows 100 times the electrical knowledge of his gramps with 30 years of wrenching.
I helped a friend who gas warm air system failed, went through 3 service calls to a big HVAC shop with no resolve. I changed the logic board and found a miswired transformer, many years later and its been solid. The problem with high tech isn't always the tech, it is likely the tech nician.

 

[sms1974]

let me throw one thing out that you have all missed with the idea of using the pool water as a source water for the geo unit, antifreeze...

A little background here, I am a HVAC guy owner / opperator of a 40 plus year old company. we specialize in air to air and geothermal heat pumps in northern Ohio.

I'll through out a few points to consider...

If you do not have natural gas available geothermal is going to be hands down your least expensive system to heat and cool with as far as a monthly bill goes. It will also be hands down the most expensive system to install. you will need to use two separate systems, one for the house and one for the pool. these systems will most likely be given separate loops, the underground part. As for costs your loop is probably going to be less than half your costs, if this is a new home I'd go so far as to say about 1/3 of your total cost is the loop.

Yes repair costs can be very costly but many manufactures now have standard 10 year parts and labor warranties, and extended warranties are available and reasonable as compared to repair cost. Average life of a geothermal unit is 18-20 years, yes I've replaced units that were 7 years old and units that were 25 years old.

I for one will agree geothermal equipment costs are ridiculous as compared to air to air heat pumps. Raw materials wise there is less in a geo unit than a split system but my wholesale cost is more than double the price difference for a geo. The 30% credit is not limited to anyone and is a straight credit if you get a return you get that 30% back in your check, if you pay that 30% credit is applied to what you would owe.

without seeing anymore info than you have given I would not balk at an installation estimate for both systems in the $40k range, take 30% off that off and your looking at $28k... lets say an air to air system for the house and an air to air pool heater installed is going to run you $20k, an $8k difference. look at your operating costs. Geo in a 4000 sq foot house and a pool is going to run you $200 a month conservatively, air to air will run you $300-$400 a month depending on air temps and energy cost per kw. So at worst your looking at about 7 years to cover the cost difference and yes the life of the system to break even, or as little as 3 years to cover the difference and 15 to cover the costs...

find a good dealer in your area and talk to the electric companies they will be able to answer your questions with exact numbers...

scotty

 

[jwvess00]

Hi there!

My house was built in 1990 (not by me) with a geothermal system in central Kentucky. I bought the house last year, and the system needed to be replaced. I wish I had known that at the time, but my home inspector was not on his A game at the time...

I had the old system removed but kept the existing wells. I also added a whole-house humidifier and an electronic air cleaner. We also replaced the ductwork -- it was originally foil-faced board, and it was leaking and deteriorating. We replaced it with insulated metal ductwork.

For all of that, in a 3-ton system (Climatemaster Tranquility 30, roughly equivalent to a 30 SEER air-to-air heat pump though I'm told that geo systems aren't rated in SEER), the total installed cost was just under $18k, and there is a 30% credit back on the geo part (but not the ductwork or air cleaner and humidifer).

I could have used a traditional heat pump, but not gas heat since there's no gas in my area unless it's a propane tank. I had to replace the heat pump in the house I sold when I bought this one (it died the day I listed it for sale ), and that 2-ton system (inside and out, but not ductwork or electronic air cleaners, etc.) was $5600 for a Trane 13 SEER by the same place that did my geo system. I didn't quote it when I had the geo installed, but I'd assume a 3-ton air-to-air at a 20+ SEER would have been double that. At that point it wasn't much more to keep the somewhat more efficient geothermal system, and be able to advertise that it's a geo system if I decide to sell later.

 

[cdd1]

Thanks everyone for the responses. To answer one of the questions, if I don't go geothermal, I will have NG heat.

I'll be sure to bring it up with the builder and see what he thinks/speak to the utility company.

 

[theoldwizard1]

Thanks everyone for the responses. To answer one of the questions, if I don't go geothermal, I will have NG heat.

Thinking out of the box ...

A multi-zone, non-geothermal system IS a via option. I don't think ANY general contract would know enough about this alternative, especially on a larger home. No special framing required, except maybe some 2x6 interior walls for piping. Each zone has its own controls.

And NO DUCTWORK !

Of course, if I was building a house, I would use structured insulated panels (SIPs). Best insulation !

 

[volleyball]

Out of the box? It looks like a typical modern boiler system. You do have to be careful mixing your "radiators" as some may heat up quicker and therefore cool down quicker by others with be slow to react. It can all be designed with that in mind.
And you could use a water- water geo system to power it.
You have pipes instead of ducts. Not my choice if I were building.
Pipes are easier on retrofits. But what about AC? I spent a lot of time with the HVAC duct designer going literally over every detail. What a pain I was but in the end, the system heats and cools flawlessly with cold or hot spots anywhere. Basement headroom has had little loss. If you ever went in a basement and had to duct to get around the trunk and branch lines, you know what I am talking about. The crew had a few choice words installing but in the end, honestly said it was the nicest job they had ever done.

 

[yeldogt]

With NG available I don't think you will find that the payback is worth the cost.

 

[Rookie2]

A few years before you bump into that breakeven point you will be replacing your indoor units. How many people have an a/c system last 15 years.

 

[kj_mustang]

My heat pump is over 20 years old.

 

[sms1974]

I see a lot of heat pumps and a/c units that are 15+ years old... yes some fail prior to that...

to the OP, if you have natural gas available it would be foolish to go geothermal...

 

[theoldwizard1]

Out of the box? It looks like a typical modern boiler system.

You must have missed the fact that I was recommending a multi-zone heat pump system. I have never seen a hot water system that used a distribution box.

Each of those individual lines is actual 2 lines They carry refrigerant. Each room has its own totally separate controls. Each unit can heat or cool.


Check out this video on Mr. Slim eight zones split Air conditioner installation.

 

[TheEquineFencer]

I'm not an HVAC guy, but let me throw this out. I have a friend that all he does is dig the trenches for another guy to lay HVAC Freon lines in, then he covers them back up. From what I understand, it's like putting the condensing coil in 50*- 55* water/soil to condense the Freon instead of 75*-100*+ air. The actual ground is the heat sink. Otherwise it works like a normal HVAC system with either LPG/ NG / electric back up for heating.

 

[theoldwizard1]

I'm not an HVAC guy, but let me throw this out. I have a friend that all he does is dig the trenches for another guy to lay HVAC Freon lines in, then he covers them back up. From what I understand, it's like putting the condensing coil in 50*- 55* water/soil to condense the Freon instead of 75*-100*+ air. The actual ground is the heat sink.

What you just described is the "geothermal" part of the title of this thread.

Some places it is cheaper to drill a well shaft and run a loop to the bottom and back up,

 

[sms1974]

I'm not an HVAC guy, but let me throw this out. I have a friend that all he does is dig the trenches for another guy to lay HVAC Freon lines in, then he covers them back up. From what I understand, it's like putting the condensing coil in 50*- 55* water/soil to condense the Freon instead of 75*-100*+ air. The actual ground is the heat sink. Otherwise it works like a normal HVAC system with either LPG/ NG / electric back up for heating.

The loop as it is typical called actually takes the place of the air that would blow through the condenser ( out door unit ) in a regular system, the flow center or water pump replaces the fan.

your correct with your example

"it's like putting the condensing coil in 50*- 55* water/soil to condense the Freon instead of 75*-100*+ air. The actual ground is the heat sink."

 

[pseudorealityx]

I see a lot of heat pumps and a/c units that are 15+ years old... yes some fail prior to that...

to the OP, if you have natural gas available it would be foolish to go geothermal...

Do you know how I know you live in a cold climate?

 

[TheEquineFencer]

What you just described is the "geothermal" part of the title of this thread.

Some places it is cheaper to drill a well shaft and run a loop to the bottom and back up,

I think when you do it with wells, you need two, one for the coil and then one to pump the water from the one with the coil to the one w/o a coil to keep the water from getting hot in the "coiled well." I think the draw back to doing a coiled well, is crud starts building up on the coils and doesn't conduct the heat exchange as well. Just what I "heard." Direct bury cost more to install, but done properly are maintenance free, they use a lot more "loop." That's from quizzing the guy that buries the lines. I've looked into doing a "total loss system" for my shop. Pumping raw ground water through a heat exchanger and dumping the water in the ditch behind the shop. I've got the well and the exchanger, I just need the time. Not trying to high-jack the thread. Please do not reply to the later section unrelated to the OP post.

 

[theoldwizard1]

I think when you do it with wells, you need two, one for the coil and then one to pump the water from the one with the coil to the one w/o a coil to keep the water from getting hot in the "coiled well."

Both methods are used.

 

[theoldwizard1]

Pumping raw ground water through a heat exchanger and dumping the water in the ditch behind the shop.

That would not be allowed in most locations.

 

[theoldwizard1]

With NG available I don't think you will find that the payback is worth the cost.

Payback rate depends on many things. In areas where you do more cooling than heating, a geothermal heat pump would pay back quicker than a forced air natural gas and a typical A/C system.

Split systems with multiple indoor distribution heads make sense for new construction (no tear up of finished walls). They also work well (lower cost of operation) for well insulated buildings because you only heat/cool the rooms you are using at the moment.