The Washington Post

Geothermal Energy

Mar 02, 2010

Christopher J. Gearon discussed converting his home to run on geothermal energy.

Hi everyone. Christopher Gearon here. Thanks for sending along your questions about my family's journey into geothermal energy. I hope to shed some light over the next hour about our experiences in going green.


Where can I get a good book on the subject of geothermal air conditioning and heating? Everything I've found seems to be vague or like some kind of text book.

That's a great idea for my next book project!

I too looked for books early on, and largely found textbooks. That's not the best starting point, as they are too technical.

Here are some sources I found helpful getting started: 

U.S. Department on Energy: (Overview of geothermal energy) (geothermal heat pumps)

California Energy Commission’s Consumer Energy Center’s site:

International Ground Source Heat Pump Association

Geothermal Heat Pump Consortium (trade association for the geothermal heat pump industry)

And then talk to people, get contractors out go bid on a potential project (and pepper them with all kinds of questions).

We had a heat pump...once. Is geothermal heat warm heat or is it cold heat, as we found with the electrical heat pump? We replaced it with a natural gas furnace and have been much warmer this winter. Since geothermal also acts as a heat pump does it offer a warm heat?

We've been warm, thankfully. Traditional heat pumps move air and work to extract heat from the air (in the heating season). That's why heat pumps generally get a bad rap, because when it's really cold outside they have to work that much harder to extract the heat from the cold air, and homeowners with traditional heat pumps complain that the house doesn't get warm (enough) in the really cold weather.

Keep in mind, the starting point for the geothermal heat pump is in the mid- to upper 50s. It's coaxing heat from the fluid in the loop. So the starting point is closer to the desired temperature. The geothermal heat pumps don't have to work as hard, and they are more efficient. We've been pleased, even during this colder-than-usual winter.

What heat pump unit did you select and why? Thanks.

ClimateMaster. Two of the three bidders recommended the brand and model. I looked at the specs and went on some forums to see if there were major problems or not (didn't see any). It -- along with many other brands -- is listed as Energy Star-rated products that qualify for the tax credits. 

So if the air is 'naturally' 58 degrees or so, can I have an awesomely chilly house in the summer for next to nothing?

Thanks what we're hoping. We've been focused on the heating season so far. But we're really looking forward to chill out this summer.

Congrats on using geothermal to beat global warming. Hope as a society we can also use geoengineering to absorb carbon and to make our world safer.

Thanks. It feels good to save money (a lot of it in the long run) and doing our part for Planet Earth.

I've been surprised that when alternative or renewable energy is talked about in the larger conversation, geothermal is typically not in the mix (at least at the residential and small commercial level).  Solar, wind and other alternatives are often mentioned. 


Is there any way that a geothermal system can be used in conjunction with a radiant floor or free standing radiator heating system. If you don't like forced air heating, is this a possibility?

Yes,  on the radiant floor heating, and I believe on the radiator scenario as well. I know someone who hooked up the geothermal to melt snow and ice on his driveway. You can also heat pools.

We actually have a screened-in porch that we may capture as part of a family room down the road. Because of that, we put in the geothermal system and set up the hot water in a fashion that we can easily do radiant floor heating should we do that project in four to five years. 


Is there a generally accepted payback time for geothermal systems?

Geothermal provides a quicker payback compared to other renewable energies, I've been told several times.

Each person's return on investment will differ based on net costs. With the tax credits available to us in Montgomery County, Maryland, we've calculated ours to be about three-and-a-half years on the geothermal alone.

How much land do you need to install geothermal? We have one-fifth of an acre with a house in the middle. Is this enough space? Thanks.

In short, geothermal can be done in many different places, and even on small plots of land. You don't need much property for the vertical closed loop system we did. 

I've been told there is an engineering solution for everything. Of course, that could impact cost. Most likely, any limitation is based on the rules of your local jurisdiction.


Someday I would love to be able to build my own house with as many renewable sources as possible. A geothermal system, wind turbines, solar...the whole package. You mentioned the cost to have the system installed in your article. Are the costs lower with a new construction situation? Or does it cost about the same for a retrofit like yours?

As a general rule, geothermal makes the best financial sense when you're building a new. It also makes sense if you do a retrofit or replace an aging system. The financing of the geothermal when building can also be an advantage. 

Wouldn't it be more efficient to heat several homes (or an apartment building, block of townhomes, etc.)? So for example, get a group of neighbors to share the cost of drilling the "shared" deep hole, and then run piping near the surface to each individual home? Related question: How easy and how reliable is the calculation for deep to drill a (vertical) hole for geothermal use in heating/cooling a house of a given square footage in a given climate?

I think you're on to something. I asked myself and several of the contractors that same question. No one could come up with a reason why it couldn't be done. I think it comes down to thinking a bit differently.

Second question: As a rule, you drill 150 feet for each ton your system your home is outfitted with. We have a 4-ton unit, but went deeper for a couple of reasons. The primary reason is the possible renovation we may do on our home in four to five years that I mentioned previously. I figured I'd also plan for the future.

Are the same, or similar, breaks available for those of us in Virginia? If not, do the additional years of payback make this financially feasible?

In a nutshell, not quite as good, but there are some available.

Maryland offers a grant program and residents can get up to $3,000 for going geothermal, depending on the size unit.

Virginia offers up to $2,000 rebate on geothermal heat pumps. 

Both Virginia and Maryland offer larger tax incentives for commercial buildings.

Check out -- a great resource to track down the financial incentives offered in your neck of the woods.

Montgomery and Prince George’s counties offer really nice property tax credits, and some other Maryland counties also offer financial perks.

Local tax incentives in DC and Virginia do not seem to be as robust. 

Meanwhile, check out Energy Star program’s details on saving with geothermal heat pumps/energy  

Regarding the additional years of payback: that's a personal decision, and you've got to run the numbers. But I'd say yes.


Can two houses share the same system?

I don't see why not, but you'd have to be on really good terms with your neighbor.

How much damage was done to your yard/landscaping when the holes were dug and pipes placed?

More than we expected. If we did what we ended up doing from the get go, we'd have half the landscaping to do.

I got an estimate to seed for $400 and to sod the areas for $1,400. Otherwise, it would be about half that. In the end, I may see or sod myself. Still, that's better than the landscaping for a horizontal system.


What nominal tonnage is your heat pump unit? And how did you determine how deep the wells needed to be dug? Usually you need one test well to calculate the conductivity of the soil.

4-ton unit. We drilled for a 5-ton unit (went deeper) for the reasons explained above.

Hey there. You mentioned in your article you had been spending $3,000 per heating season on oil. How many gallons did that amount to typically in your part of Maryland? (Eg. how much were you paying for a gallon, including taxes, delivery, etc.?) Also, what is your heating strategy for extremely cold periods when the heat from the ground gets used up very quickly?

The associated costs and savings will be fodder for a follow-up piece.

In terms of back-up source of heat, we will rely on our high efficient, tankless hot water system (which runs off propane) as our back-up source of heat for that "one to two percent" of time the geothermal can't keep up because it gets so cold or should the system go off line for any reason. Good news is that even during this cold winter, we haven't had to rely on back up.

Is it preferable to have a system where the pipes make a run that's more horizontal around the yard or one where you just drill a couple hundred feet down? Is there a big cost difference between those two?

It was preferable for us to go vertical, as I mentioned in the article, both cost wise and as a practical matter.

You would definitely need some land for the horizontal set up. I've read conflicting reports about the costs. From my personal experience, the bid we got on the horizontal set up was several thousand dollars more than for the vertical closed loop system.


What permits were needed for any part of your installation, and were any a pain to get?

Yes, permits are needed, and we also had a couple of inspections. You're going to test my memory on this. One was needed from the state for well drilling, if I remember correctly, and the county needed to provide a permit, too. A county inspector also came out to see that it was done properly (at the end). Our hot water set up also required permits and inspections. All of them were painless, as the contractors handled those.  

Home builders in the metro area are not willing to install geothermal heat pumps in homes (in developments) or even leave the furnace out and allow the homeowner to do so. How are we ever going to change if those building new homes aren't able to make the switch?

I remember 10 years ago, no contactor would install a tankless hot water heater, even though they are the standard in many parts of Europe. That's changed here now.

I think the geothermal is the same. The more people hear about it, ask and demand it, the more things will change and become easier. 

Regular heat pumps really start to sputter once it gets below freezing. At what air temperature do the geothermal units loose their effectiveness?

Traditional heat pumps work differently than geothermal heat pumps as the starting point for heating and cooling. The starting point (in this area) is mid- to upper 50s in terms of the fluid in the loops that is brought into the geothermal heat pump. So the efficiency problems that traditional heat pumps suffer (i.e. extracting heat from cold air) isn't applicable to geothermal heat pumps. 

Is a backup system necessary? What could go wrong with the geothermal and how long would it take to make repairs?

Whehter one is need or not I'm not positive. But all three bidders included that as standard operating procedure. I look at it this way: Before if my furnance went out, I didn't have a back up source of heat. Now I do, if the geothermal heat pump goes off line or gets into the "one to two percent" of time where it needs a bit of help because it is so cold out. Again, we haven't found a need for the back up during the recent cold spells. 


Thanks for all your great questions. Gotta run.

Thanks for all your great questions.

Gotta run!


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