What is the Straight Dope of Geo-Thermal Heating and Cooling?

Factual Questions
1

As oil prices skyrocket I am beginning to believe that this can be a money saving option. My Central Air unit is older and should be replaced in the next few years, but it might make more sense to go Geo-Thermal instead.

I am wondering what it would cost to install and then what it actually costs to run.

I assume my baseboard would become useless and that geo-thermal is a force air technology. Is that correct?

What do I need to know and what do I need to find out?

I am of course trying to start my research on the web and this is part of my research.

**The facts: **
I live in Central Jersey.
I have plenty of property to run the pipes. (2 acres in fact.)
I have central air ducts already in the ceilings of all rooms but the main two bathrooms.
I have baseboard heat with an efficient Oil burner on a programmable thermometer and I keep the house fairly cool.
I estimate I spent roughly $3000 on oil last year. Five years ago it was under $1000.
I have a good working well for the hose bibs and I know the water table is excellent here.

Jim

2

The best resource for the industry:

1-888-ALL-4GEO
www.geoexchange.org

3

Heat flow from the ground in Jersey (national map ) is less than 50 milliwatts per square meter.
You have to drill down 4 kilometers to hit 75°C.

-Lots of nice maps here .

4

That is not my understanding of the requirements. The heat pump does not require that type of heat to work. Of course that is why I have started this thread and my homework on the subject.

5

Squink, I think you and the OP are conflating two very different technologies.

Geo-thermal power is taking heat from the earth to generate power.

Geo-thermal Heat pump technology is an alternative heating and cooling system for buildings that makes use of the relatively stable temperatures several meters below ground surface. By running a refrigeration/heating cycle using the ground temperature as either a heat source or a heat sink, a building can be heated, or cooled, for a fraction of the cost of actually generating the actual heat increase through energy conversion.

6

Yup, What Exit was talking heating and cooling, and I immediately thought power. Oops!

7

In your “facts” you left out the size of your house. However, assuming that your force air system is working properly and sized properly for your house, then your ground source heat pump will be the same approximate tonnage as the air conditioner that you’re replacing.

I live in Michigan. I had a Waterfurnace Premier installed to replace my 1984 model forced gas furnace and air conditioner. It is a 3.2 ton unit. The original air conditioner was a 3.5 ton unit.

I also opted for an auxiliary resistance backup heather. This is recommended, because you don’t want to oversize the heat pump (just as with air conditioning). If your engineer does the sizing right, it’ll only ever kick on on the very coldest days of the year.

I also opted for a desuperheater and an additional water storage tank. The desuperheater keeps the water in the storage tank (just an 50 gallon electric hot water tank not connected to electricity) hot, and feeds this water to my old gas heater as my demand drains it off. When the system is operating, it’s free hot water (little bit of current to run the desuperheater circulator pump).

My property is just shy of 0.5 acres, and the ground loop only took up about 1/3 of my back yard. If it breaks your heart to destroy your lawn the way I did (it’s coming back, though!), you could opt for the more expensive process of hiring a well digger and going vertical. It’s considerably more expensive. If you have a pond, that’s another installation location option. Or you could use an open loop system with your well water.

Oh, I also get the electricity for 1/2 price. That means that even ignoring everything else, it’s now only half the cost to cool the house in the summer as before. The real savings, though, are found in the natural gas. I don’t recall my savings (maybe I posted them here in GQ in another thread), other than they were significant. I currently have an $800 credit on my natural gas bill due to the reduced consumption, though. My average monthly electric bill (I do the average payment scheme) shot up from $78 to $97. Like I said, I’ve not looked at the figures since looking at my winter savings, and will do so later this year to look at summer savings. I think I will actually beat the expected payback, though!

Oh, yeah, it will use your existing forced air system, and make the baseboard heat obsolete. Another thing I like about my system (and I’m led to believe this is true of all high-efficiency systems in general), is that it doesn’t live up to the bad reputation of “forced air” systems that I’ve heard and experienced growing up. It has a variable speed motor, and the hot air isn’t as hot as all the old systems. It cycles longer to compensate, and thus avoids all of the hot-cold cycles that I was accustomed to. That also makes it quieter. That wasn’t something that I was expecting or even shopping for, but it was quite a pleasant bonus, and now I’m spoiled by it.

Cost? I looked at some high efficiency systems. I’ll just say I ended up somewhere between $10 and $20 grand, including the landscape repair. It was about 50% higher than the high-efficiency systems I was looking at. The payoff will be quicker, though, and within 6 years or so, I’ll be ahead.

8

Why?

9

Oh, it’s the “electric car or alternative hvac” rate. Something to that effect, anyway. It’s a separate meter from the rest of the normal stuff that’s still at full rate.

Aside from just the AC portion from being cheaper due to the rate (not including efficiency improvements, even), I realized that my ancient, single speed blower motor was running at the full rate, even during heating season. Now it runs at half rate, too. I didn’t realize how significant that is, and it took me a while to figure out why my main meter electric costs had gone way down. Non HVAC power costs less than city water!

10

Balthisar, thank you very much. The price is higher than I was hoping for, but I don’t think I need to worry about the landscaping. My grass always comes back quick.

I believe the living area of my house is around 2400’ square. I think my AC is a 3 ton unit. I will verify all of this before I start calling around. I was expecting to the ground loop and the 2 acres will handle that with ease.

Instead of the supplemental heat auxiliary resistance backup heater, it sounds like I could just run my oil burner base board. Also I doubt NJ gets as cold as Michigan. The boiler and burner are only about 5 years old.

I love the bonus of eliminating my electric water heater. That appears to be my main electrical draw. I have a 6700W solar power panel system so my electric is not bad, especially compared to my neighbors.

What temp does it get the hot water to? My wife will kill me if it is not hot.

I have some hopes of doing this project for $8,000 to $10,000. Do you think that is at all feasible?

I should have mentioned, I intend to remain in the house for at least another 17 years.

Jim

11

Maybe… you’d have to talk to your installer to see if it’s compatible with the control system for the geo unit. The idea is, the geo unit will turn on and off the auxiliary system as needed by itself.

Keep in mind that when you’re not heating or cooling your house, then you’re not heating your water. Also, if you’re not drawing off hot water, then you will cause the secondary system to fire up. That is, the “main” (desuperheater reserve tank) tank supplies the “backup” tank, from which you draw water. My backup tank is the gas tank; yours would be your current electric. If you don’t draw from the backup tank (i.e., fill it with hot water), its water will cool off eventually, causing it to cycle on! In other words, don’t worry about “saving” hot water! Well, unless you use too much at one time.

Mine heats to 130 degrees before it cuts off (i.e., stops circulating water through the desuperheater). It’s plenty hot. I keep the gas burner at 120 degrees.

Probably not, unless you can do a lot of the work yourself. Or… if there are a lot of companies that do it. Part of the problem here is, there are only three companies in my entire region that do geo units.

Heck, even if you have to pay 50% to 100% above the figure you mentioned above, it will certainly be worth it if you’re going to stay in your house that long!

12

Thank you again. I don’t have gas available, so I would still be stuck with the Electric Water heater for part of the year if I understand correctly. Sounds like it is plenty hot enough though.

I have already found at least 5 installers in my area and that was with a minimal check from a green resourse that listed my Solar Panel Installer. So I can hope.

I will do more of my hopework tonight.

13

From what I’ve read, there are two different styles of geothermal. One uses drilled well(s) with a glycol solution circulated through them and a heat exchanger. The other uses a series of copper ground loops through which the refrigerant is circulated, eliminating the efficiency losses of a heat exchanger. One article described a radial boring unit placing holes around a central point on downward angles (think of downward facing daisy), those holes being filled with a protective grout, such that the copper isn’t subject to corrosive ground effects.

14

Have you checked into any applicable tax rebates or other subsidies?
If I may be so bold, you may not wish to limit yourself to a purely dollar to dollar comparison, if the geo system will make you feel good about your choice - and there are numerous ways such a decision could make one feel good.

15

Well the other part of this is the better Green footprint of Geo-Thermal. When I bought my Solar Panels, the pay back was going to be 11 years (after large rebates) and we chose to do it as a social investment. Electric unexpectedly took a large spike and now the social investment is looking like a damn food money investment too. So it was a win win. I would like to do the same with the Geo-Thermal.

As to tax rebates, that is a big part of my homework. We got into a program with the State of NJ as very early adopters of Solar so that they paid for 70% of the panels and installation.

16

We just got a geothermal unit installed two months ago in the home we just purchased. The home used to have fuel oil and no AC. When our specialist came out, he put the figures in his computer, compared it to propane and electric just to show the various savings because no matter what we needed to replace the furnace. For a 2700 Sq. ft. home it would take about four years to pay for itself vs. fuel oil, six for propane, and eight for electric. With the recent fuel spikes, I suspect it will take under four years to pay off the geo unit.

You’ll have to excuse me, because I forget the ton-age of the unit, however in the last two weeks it’s cooled very nicely, and the place must be well insulated because turning it off at 74 deg. on an 86 deg. day it never did get above 80.

We too have the backup heater, I’m sure it will come in handy. We didn’t get the closed loop system, though we wish we had sprung the extra $1,500 to do so. We’re thinking of installing a cistern to use some of the runoff for watering the garden and lawn.

17

Can I ask what it cost you?

I am only heating and cooling about 2300 Sq. ft, I checked my drawings. The garage and basement do not count.

I’ll have to check the current AC compressor later in the week.

18

Do these units come with any guarantees of function and efficiency? My father’s house was built in 1985 with a heat pump, but it couldn’t keep up with even the Maryland winter. He eventually had a conventional gas unit installed. Of course, the technology has probably improved considerably in 20 years.

19

Sure! It was $13,500 for everything. That was removal of the massive unit that was there before, a new pump for the well to keep up with the water demand, complete installation. Ours doesn’t include the basement or the garage in the Sq. Ft either.
And total time spent on the project, about a week. We had to wait for the unit to be built and shipped from Florida, took about two weeks for that, but ground breaking and install was a snap.

Figaro, When our specialist came in, they did tests to check the house for a compatibility rating basically, and our quotes were drawn up upon that. They did some number jumbling with expected heat loss and the like. I don’t know about a guarantee per se, but they were very professional and checked all spaces in the house. They also explained the differences in the models, and why we needed that ton-age for the house we had. While the 3 ton was going to do the job, the 4 wouldn’t work as hard, and be more efficient. And the cost difference wasn’t enough for us to consider the smaller unit.

Yes, I called my husband and he confirmed we got the 4 ton.

20

I see - I guess I’d feel pretty comfortable doing that. My guess is that my dad’s unit was a pre-fab designed for new-construction homes that wasn’t appropriately sized. He wouldn’t have given up on it unless it was an epic failure.