Geothermal Myth #1: Geothermal Heat Pumps Don’t Work In Extreme Cold

With all of the information available on the web, we wanted to take the time to dispel a few of the myths surrounding geothermal heat pumps in a three part series. Today, Geothermal Myth #1: They Don’t Work in the Extreme Cold.

The myth that geothermal heat pumps do not work in cases of extreme cold is often derived from the fact that standard air source heat pumps do perform poorly in below freezing temperatures. A ground source heat pump is NOT an air-to-air heat pump.

A number of homeowners in the Northeast have complained that air-source heat pumps do not have the ability to produce enough warm air when the outdoor temperature drops below freezing (which it often does during those brutal northeast winters). The differences is that when the outside temperature is below freezing (say 15 degrees Fahrenheit) the temperature underground is still somewhere between 45 and 55 degrees.

So remember that 400% efficiency that your geothermal heat pump has? Well it’s still there! Just because the temperature outside drops does not mean you need to worry about your geothermal heat pump’s ability to keep you warm.  Your geothermal heating will function however it simply needs to produce more heat to keep up (meaning it will run longer). Most systems will have an auxiliary heat backup (electric) to ensure the system always provides sufficient heat. This auxiliary heat should only come on during the coldest days of the year. Problems arise when the auxiliary heat runs constantly – this would result in a very high electric bill.

You will find many upset homeowners who curse geothermal systems. We certainly will not hide the fact that there have been plenty of disastrous installations out there by inexperienced contractors. You’ll find these stories in the comments below. These situations are extremely unfortunate and the frustrations by these homeowners are completely warranted, however, its not the technology – its the design. When a system is not designed correctly it fails – think of it like trying to tow a large boat with a Honda Civic. Finding a quality geothermal contractor is absolutely the key to geothermal happiness. Ask for references from systems the same company installed 5-10 years ago, if they don’t have them then don’t buy!

Geothermal Myth #2: My Geothermal Unit Will Need a Backup

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Comments (23)


  1. Meryl Haslam says:

    My expereience has been quite different. In extreme temps (below 0 in winter, 90+ in summer), my geothermal system just doesn’t perform properly.

    As an example, it was 90+ degrees yesterday. Thermostat was set to 73 and the house temp stayed at 76 all day. I even tried setting it to 65 and it made no difference. Same problem in winter. Set it to 72 and it won’t budge over 68.

    This is a 6 year old WaterFurnace System
    Any thoughts would be welcome.

  2. NAGU says:

    i have dx exchange geothermal installed in my house
    it keeps the house warm when temp outside is above 40 degree F…but when temp falls below the house gets cold …Ranco temp from the system will be around 70 and water temp is around the same,…

  3. Ronda Dennis-Smithart says:

    We have geothermal x 2 yr, satisfied until last month when our electric usage almost doubled what it’s been previous winters. Last month $600! Had tech here, who reported our outgoing temp vs incoming is 10 degrees different, but ground temp is only 34 degrees so the unit can’t keep up, and auxillary heat has been needed. We have 3 geo in an office building, and bills have been less than 200, which is in line with previous bills. Tech could find nothing wrong, anything we can do? Location Iowa, temps below zero.

    • Robert says:

      Do Not know if you ever got your answer. But if you system is Closed loop (Pump you water in pipes that have antifreeze in them) then your issue was/is Low temp loop setting. On Climate Master a jumper on the board must be cut to allow it to run the fluid temp lower then 34 degrees.

  4. Sally G says:

    My geothermal heating system works great until the temps here in Virginia dropped below 20F. The thermostat is set at 70F downstairs and will only hold at 62. The upstairs is even colder at 58. What is going on and how can I have it warmer in my house.

  5. Dr. Jan Herman says:

    That’s what I was led to believe which brought me to spending $70,000 to convert my 5000 s.f., three-story (plus full basement) home to the (what I was told) is the largest residential (5-ton; 2-ton water-to-air & 3-ton water-to-water) geothermal installation in Northeastern PA (Climatemaster) in March/April 2013. Meanwhile, during the last three weeks (since about New Year’s Day 2014), the temperature outside has dropped (and remained for up to four days straight) below freezing. It has often gone sub-zero out there. What I have been dealing with, as a result, is a repeated freezing up of the system leaving me with no heat save for my emergency, electric backup for sometimes days at a time. This system, which I LOVED during the summer and fall months, has become a nuisance at best since it got (and stayed) very cold outside. Care to elaborate given your above statements? Thanks.

    • Larry Jones says:

      We have virtually the identical geothermal system at our house, newly installed, summer 2015. Southeastern PA. (5 Ton – Climatemaster)System worked great during summer season. During recent cold snap of temps below 20 F, the system was not able to heat above 69 F and it ran continuously!. Very disappointed.

  6. Karen Massey says:

    I installed a geothermal unit 4 years ago. Now I am having problems when the temperature gets down to 20 with the geothermal until switching over to auxiliary heat (ie emergency electrical heat which is VERY high dollar). My contractor now says the geothermal units are not designed to heat in weather that is below 20 degrees. I’ve never heard that statement made before. Is that true? Does anyone know the truth?

    • mcderven mechanical says:

      The biggest issue with ground source heat pumps is application. A ground source heat pump will transfer the same amount of heat all year. Whether you are transfering from ground to house (heating) or house to ground ( cooling ). What happens in the very low temperatures is that the heat transfer from inside to outside increases. Therefore the btu output in not enough. For example this is based on a normal year in the ottawa area. During cooling inside is 70 and outside is 95 = 25’f difference. During heating season inside is 70 and outside is -4 = 74’f difference. A heat pump is sized slightly larger than its cooling application. More often then not the heat pump does not supply enough heat during the winter months and the backup kicks in. The introduction of the 2 stage heat pump has helped this situation greatly. A typical application for a heat pump is a new efficient house.

  7. Travis says:

    I work on GEO Thermals on a military base where atifreeze is not permitted. having temps of 32 going into house and 40 going out this year was the coldest weather on south west Oklahoma in years. Could not heat house with that temp of water in loop with no heat strips to help out, as soon as it warms up it works great. What options do i have?

  8. wolfpack says:

    The #1 Issue in geothermal today is improper system design which usually means the loop field (the outdoor portion) is UNDERSIZED which causes very high electric bills in the winter (because the backup electric is running too often) and inability to cool in extreme summer temperatures. This is a real issue in the industry today and its why we stress the importance of a quality contractor and to NOT chose on price. Some quotes have less loop field which leads to these types of concerns down the line.

    • Dale Binkley says:

      I tend to agree with wolfpack. Our system is 6 years old. A couple of the winters we have been through have had extended periods below freezing. Even with the cold spells, it is rare that our backup heat comes on at all.

      The first winter our system was in operation we had a couple weeks where the temp outside only reached 20F during the day and was usually around 0F at night. Our system ran longer but kept the house at 68F. We found out in the spring that our backup coil heater had not been connected and did not work at all during the winter. We were pleased that our system was able to keep up. In spite of this oversight, we saved at $1000 the first year our unit was in operation.

  9. Ben says:

    I have a 600′ closed ground loop for a 4 ton system. When the temperature outside is 20 degrees or colder for an extended period, the loop gets too cold to keep up. The longer the cold spell, the colder the loop becomes and the less effective the heating system. In 4 years of operation, It did not keep up for 12-20 days total. I have no strip heater or backup of any kind and I’m considering adding one now. I am sure if I over-sized my loop, this would be less of an issue but extended, lower than expected temps, will cool the loop more every hour.

  10. Kathy says:

    Our 2-year old geo has been a nightmare. We are cold, broke, with a ballooning carbon footprint (due to auxiliary electric heat being on so much). We used an IGSHPA certified contractor with good word of mouth in the area. It’s a weekend house. By mid winter, the system doesn’t keep the house (1450 sq feet near Albany, NY) much above 62 when the temperature drops below 25F; it “froze” last winter. Auxiliary heat is on frequently, high electric bills (worst months at $700-800 for weekend heating when contractor had told us to expect $100 for full time heating). Contractor said first year that poor performance was due to opening ground for install in November; also said that we need to do spend another $8k for more insulation (we had done what he recommended at install). Following year he refers to more insulation needed; now tells us that it takes systems 4-5 years to “settle in” to maximum efficiency. (Is this possible or just an excuse from him?) We have been burned with our attempt to be kind to the planet, and are looking to install a supplemental propane furnace. Does anyone have experience with this? When do you use the supplemental? When the geo runs out mid season or as a boost on the coldest days throughout the season? On a happier note, geo A/C has performed beautifully.

  11. Shannon says:

    I just paid $35,000 for a geothermal system and was assured that it would keep me warm this winter. It is not even January yet and the system is going into a freeze error and the emergency heat is coming on. It appears I have been lied to. I thought I was dealing with a reputable contractor. Now what to do!!!!!!!!!!

  12. Jack says:

    I have to say, Geothermal is useless in winter! I bought a new home with a Geothermal system pre-installed (didn’t have to pay extra for it). I am in Canada and over the fall (temps between 30-45), the system worked brilliantly! My energy bill was super cheap…but as soon as the cold winter (20s to -10s) kicked in the system is useless! I can’t keep my home temperature above 65 and the auxiliary heat pump kicks in most times, which obviously made my hydro bill go crazy – $450 alone last month.

    At this point, I am seriously planning to replace the whole system with a gas or electric one with zones.

    So a piece of advice, if you live in warmer country you might get some of the Geothermal savings back, but if you don’t…don’t spend your money and buy one, you will never recoup your investment and will have cold winters inside your own home.

  13. It sounds like people are struggling with improper sizing and perhaps over-driving the system and attempts to heat a space too fast. Geothermal works best when you heat slowly and steadily so you don’t freeze the ground surrounding the loop field.

    I interviewed our lead design engineer, who addresses these topics in this article:

    If you are having issues with an undersized loop field, get in touch with us and we can easily increase your loop field capacity without any digging or trenching!

  14. Rebecca Stone says:

    We are having the same problems as described above. We just purchased our log home and were pleased that it had a geothermal system. The house is cold during low temperatures outside and we have had extremely high electric bills. The last one was $577.00!
    If indeed the previous owner did install an “undersized loop field” what can be done and how costly would such a project be?

  15. Chris says:

    As an owner of a Waterfurnace Geothermal unit, I disagree with the title and comments the blog author. We have a certified Waterfunace dealer service our unit every 6 months to maximize its efficiency. However, like others have said, these units DO NOT hold the set temp. During the winter months we set our thermostat to 68. Last night it got down to 5 degrees here in Tennessee and the unit ran the ENTIRE night on Aux Heat but the room temp was 62 this morning. The same thing happened last year when it got below 20 degrees. FYI…The money you save in the summer is offset in the winter by astronomical electrical bills because the unit runs constantly. Furthermore, we have had to replace the blower fan multiple times (probably because it burns out from overuse) which has to be special ordered exclusively through Waterfunace costing about $900! If your considering a geothermal unit, think twice, don’t waste your money and trust the comments from those of us who have them!

  16. Cold in ohio says:

    Have 6 ton geothermal and it sucks, our loop is over 150 ft long and electric back up is always on, for the money that was spent on this piece of crap and the electric bills that hit 600 I could have bought a lot of propane and been warm


    My experience is that the system is not a good fit for the extreme drops in temperatures in Long Island NY. We had 10 below zero temps this week (my first winter with it) my electric bill is almost 3x’s what it used to be and the system shut down & my pipes froze…the fact that the company (sherman industry) filed bankruptcy after they took peoples money & didn’t complete jobs doesn’t help because they held the 15 warranty if we were ever to have a problem …so we have no one to turn to & are at the mercy of companies don’t have emergency on call service & come 24 hours later & who just want to say the system was installed incorrectly & do nothing to fix it!!! I highly recommend to anyone considering geothermal for their heating & cooling RUN don’t walk to your nearest gas installer…this is not for NYers with extreme weather conditions!!!!

  18. Ken says:

    I agree, systems seem to not work well when temps outside drop below freezing for extended periods of time. I just had a climatemaster trilogy 45 installed and I asked them to not install the auxiliary heat because I was told it wouldn’t need it (but could add it in later if I wanted). To me it seemed like a waste to put in an expensive electric backup for a system guaranteed to work in any temp I would encounter. This is our first winter. I’m in NY on Long Island and currently outdoor temps are as low at 7 at night and are averaging 20 during the day for the last week or so. My system has some really good diagnostic info available realtime. It can go for full day stretches at 100% capacity and the indie temp, whether set at 67, 68, or 69 degrees, never quite gets to where it’s set. Sometimes it struggles at 65 degrees for a whole day.

  19. Farmer K says:

    I share similar experiences for extreme cold. It is not an issue of loops – we have plenty of land for horizontal loops, eight turns and the capacity of the unit is well beyond the size of the farm home. The electric heat strip isn’t practical cost-wise. I have resorted to a propane backup zoned for the coolest part of the home. As we only use propane for cooking, the tank is enough to get us through extreme cold. I concur with practitioners – it is no myth. Sure, it could be that contractor education is not sufficient. Odds of getting adoption in my farming area are zilch as I was a first mover and it just doesn’t work when you need it most. 68 degree any sunny, no problem.

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