Is a Geothermal Heat Pump Worth It? My Net Zero Home

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[ohrosberg]

I live in Norway, and installed a similar setup to yours back in 1999, and replaced the heat pump a few years back. There is one thing you didn't mention, the option of having in-floor radiant heating system, which is basically hoses that is cast in the concrete floors of my house. That's not cheap either, but the system was delivered with a 100 year warranty, so it's also a long term investment. We love this, as our floors are nice and warm during the winter period, and our kids and now grandkids love it too, because our floors are never cold. The downside is of course that you can't really use that system for cooling in the summer, but where I live, there's no real need for that. Also, since the heat comes from the floor, we can keep a somewhat lower indoor temperature without feeling cold. One downside is that it reacts slowly to change, because you need to heat up the concrete before you heat up the room, but with a good control system, that's not really a problem. The heat pump has an outdoor temperature sensor, which means that it can react long before the room temperature changes, so that mitigates that downside to a huge degree. The heat pump also delivers hot water like yours, but in sufficient amounts to meet the need we have, with four adults living in the house. Whether it is financially profitable or not is debatable, but if you ask me if I would do it again, the answer is yes, totally, the sheer comfort of it is amazing, and the heat pump lasts for at least 20 years.

[MichaelKusugak]

Matt, I grew up way up north, at the north end of Hudson Bay, right on the Arctic Circle. I learned to make igloos at a young age. In my teens, my dad sat me down and said, "I have to tell you about the igloo." Of course, being a teenager, I revolted. I said, "Dad, I know about the igloo, you taught me how to build them." But, undeterred, he told me about the igloo. He said when you build your igloo, build it in shallow snow so, by the time you cut your blocks, you will be on bare ground. That bare ground may be frozen but it is still warmer than the outside air and you can borrow a little bit of heat from that frozen ground to help heat your igloo. Where I grew up we have something we call aujuittuq, ground that never thaws, permafrost. If you build your igloo on lake ice, make sure there is water under the ice. That will serve the same purpose. The igloo is built on the same principle as a downdraft kiln; the doorway is way down low so you have to get down and crawl in and out because heat rises and you live in the dome which is higher up where it is warmer. The coldest day I remember in Nunavut, Canada, was -52C (-61 Fahrenheit). If I had an igloo that day, I could get the temperature up to 0, 1, 2, 3 or 4. You don't want to make it any warmer otherwise your walls will start to melt and turn to ice. And ice is so much denser than snow and has much less insulation value. You don't want ice, you want snow. And when it is -52 outside and +4 inside, there is a difference of 56 degrees between the outside world and the inside of your igloo. And when you are wearing caribou skins, that is plenty warm enough to be comfortable. My dad never went to school and didn't speak English but he understood geothermal heating. It is a principle that has been used by Inuit from Siberia to Greenland for thousands of years. A very interesting topic. I enjoy your posts. I built a superinsulated house in Rankin Inlet in the early 1980, s with triple-glazed windows. I also installed a heat exchange system and it served us very well for many years.

[matthewshultz]

The 'desuperheater' concept is a fantastic way to save energy and cost when applied to kitchens. Commercial kitchens need a lot of (usually conditioned) airflow which generates heat through a normal DX air conditioning unit. Most of that heat can be used to generate the hot water for food prep and dishwashing. Normally a kitchen has a few gas water heaters, but more and more I am calling for energy recovery preheat with a gas tankless to manage final temperature. New tech is great!

[ijchua]

The key thing missing in Matt's payback is a discount rate — money today is worth more than money tomorrow. Inflation is one reason why. The payback chart showed somewhere within 14 years but without taking into account into the fact that the $20k extra upfront is worth more than the eventual payback of "$20k" spread over many years in the future. Also, at those timescales, the equipment may fail and therefore never recoup the savings.

[JohnMayfield-NS]

We did ground source geo when we built 12+ years ago, horizontal loop, desuperheater also. Our ERV is separate from the system and no whole house dehumidifier, but when humidity becomes an issue we run the cooling on geo and that takes care of it pretty fast. I forget the total cost off hand (guessing around 25k-30k), and compared to oil heat, which was the norm here, our payback was estimated at 8 years - but oil prices have only gone up and it wouldn't including any kind of cooling system. Maintenance so far has been.. changing/cleaning the filter.

I'm extremely happy with our set up and wouldn't do anything else if given the opportunity.

[fanriadho]

The richer you are, the more savings options you can choose

[danlangston]

My parents have an open loop geothermal heat pump. Pumps water out of the well and dumps it in the lake in the backyard. Unit is from 1992 and still works.

[mrfusioneng]

We also have a net zero home in South Florida, I did my geothermal a little differently, I drilled 14 vertical wells around 12ft deep, ( by hand, 4” dia with a half inch electric drill), using 3/4 lawn sprinkler tubing, so the single serial line goes up and down from around 3 ft down to 12 ft, the over to the next hole 14 times. Unfortunately the ground water temp down here is 72 degrees, the water table is only 1-2 ft underground. We then run thru a small solar powered chiller to get the water temp down to around 68 f, which then is circulated thru a heat exchanger in the attic in the hvac main channel in the attic. It works mostly on convection, with a little assist from a variable speed blower to get constant air flow thru all the hvac ducts. All the air returns down here are in the ceiling, as hot air rises, the warm air rises gets sucked in thru the returns, gets cooled by the heat exchanger, then falls out of all the hvac ceiling registers in every room, ( after passing thru filtration and a single pass uv germ system). So the house has continuous flow of clean cooled filtered air, ( several in home have allergy problems). All of our attic ducting is r30, so our worst temperature drop or rise thru the attic is only 1 degree, ( we have temp sensors at the beginning and end of every duct in the home).
Just a different approach, result is this small passive system cuts the main hvac run time in half. Didn’t cost more than a few hundred dollars, and it actually works.
Just thought I would share for those interested in a super simple and inexpensive solution.

[RobertHopkinsArt]

I am so happy to see that you put in an Aprilaire dehumidifier into your system. I have two of them installed. One in the HVAC and one of them in the crawl space below the house. It's set at 45% to help with any mold and it helps to keep the bugs out too!

[jamessheufelt]

My brother installed a Trane ground source system 25 years ago and it’s been great for him. Never a problem having enough heat in Michigan winters.

[Gwallacec]

This man got his whole house build sponsored and I can’t even afford looking at a house.

[TroyFoster]

For anyone wondering about how Geothermal systems work when scaled up for commercial properties, they work great for buildings with balanced yearly heating and cooling loads, such as office buildings located in the Midwest, USA. I'm an MEP Engineer and for commercial projects, with the accelerated depreciation option, and Inflation Reduction Act tax write offs (that include all costs for Geo, including engineering fees), we've found that if you will be owning a property for any length of time, it is actually cheaper right now to install Geo on large buildings than is it to install conventional systems.

We recently finished overseeing the installing of our GHX system design on the Michigan Capital Building in Lansing, MI.

[Austden]

Geothermal is the clear winner from a technical standpoint but seems to be best (makes the most sense financially) for bigger scale projects. A developer doing an entire neighborhood or a grid wide application.

[kyletech]

10 years ago, my parents build our family’s forever home with the same goals as you in mind. We went with commercial grade water furnaces, as it was the only things available in the size needed for a 6 person house at the time. We went with 7, 200ft vertical wells and the cost was higher than now. But, the energy savings and comfort has been well worth it. With almost 0 equipment maintenance cost we’ve been able to comfortably heat and cool our house even in the cold winters or hot summers. We’ve just installed the desuperheater option that we never did originally and it’s been fantastic for creating hot water and reducing our propane consumption. I hope your home provides the same level of comfort for you!

[marktomlinson]

I am in Ontario Canada about 100 miles north of Lake Ontario. My 4 ton Climate Master 2 stage ground source heat pump has run for 15 years with NO service calls, and paid for itself at about 8 years, as was estimated before purchase. It saves about 75 % of the electricity cost that the previous baseboard heaters used. It heats completely without using the back-up heaters down to minus 30 F. It uses a ground loop buried 5 feet down. I added a soft-start unit myself, which will extend the life of the compressor significantly. I have never been sorry I invested in a GSHP.

[willywilkins]

Matt,
we have owned a series 5 Waterfurnace for 20 years. The AC performance is OUTSTANDING. The winter heating is somewhat underwhelming so we supplement this season with a wood burner and a small LP gas room unit to heat our rural Iowan home during the cold months.

[EsotericArctos]

The variable speed is what is used in anything labelled "inverter" technology as well on heat pumps. It's been around a very long time in split systems, and is quite common. Quite a number of central systems also use the same variable speed technology on the compressor as well. It certainly is not anything new, and two stage is rare in heat pumps, mostlly two stage is used in gas furnace style heaters. It does help keep things more even and saves considerable energy cost.

[BillEichinger]

Working in Antartica we built Quincy huts for survival. They tend tend to stay 30 degrees warmer than the outside temps. Built from snow not ice blocks.

[BorderKeeper]

Our apartment complex (50 apartments) has "shared ownership" system in place and we decided in our regular meetings to go with a geo heat pump. No HVAC only water so it does not cool only heat, but considering its an old soviet style "panelák" it's the best we could do. Ignoring the benefits you outlined, which we also got, we also are now in a different bracket with our electricity supplier and so overall we have cheaper electricity per kWh as well, which added some savings to it. Don't have exact numbers, but so far it works great.

[meezerluvr]

About 15 years ago, I had to replace both AC and furnace. I compared pricing for standard AC and furnace vs. a geothermal system. After government incentives, I estimated it would take about 5 years to recoup the additional cost. I chose to go with a vertical ground loop both due to the cold climate in the area and how we used our property. The wells cost $10k. However, the results were fantastic. My house was more comfortable than ever before, and energy costs were reduced so much that I recouped the excess costs before 3 years. I've moved since then, but if I were building a new house, I would almost certainly go with geothermal.