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How Geothermal Heat Pumps Help You Save on Hot Water Heating

By Nordic

June 08, 2015

Heat Pump Installation

geothermal heat pump desuperheater
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Photo Credit: ___steph___

We all know geothermal heat pumps are ultra-efficient and can save you up to 75% on your heating costs, but did you know they can also help you save money in other areas of your home’s energy consumption? That’s right, your geothermal heat pump will also save you up to 55% on your hot water cost using a desuperheater. Keep reading to find out how the built-in geothermal water heater works.

How Geothermal Water Heaters Work

Heat pumps reduce hot water costs through a component called a desuperheater. While most geothermal heat pump manufacturers have this as an add-on, all of our residential heat pumps come with a desuperheater included for domestic hot water preheating – even our air source heat pumps.

Here’s how it works, directly from our Product Engineer, Dan Rheault, “The discharge gas from the compressor is significantly hotter than the condensing temperature, and condensing is the main heat source for space heating.  A desuperheater is a small double-wall heat exchanger that takes this extra heat from the discharge gas and puts it in your domestic hot water tank.”

In layman’s terms? A geothermal heat pump heats your home using a compressor. The compressor produces extra heat, which is what we use to preheat your domestic hot water tank. The desuperheater harvests the extra heat using a pump and heat exchanger and deposits it into your electric hot water tank.

Since we are harvesting waste heat, the desuperheater does not affect the heat output of the geothermal heat pump. Also, since we can only harvest the heat when the compressor is running (when the geothermal heat pump is operating), we can’t supply 100% of your domestic hot water needs. Instead, it is estimated that a desuperheater can provide between 50% and 60% of your domestic hot water requirements. Your hot water tank provides the rest of the heat.

Desuperheaters operate in both heating and cooling mode, but the greatest savings occur in heating mode and the savings while in cooling mode are relatively small. Overall it evens out to 55% year-round.

How Much You Can Save With a Geothermal Water Heater

Just how much can you expect to save on your electricity bill? Let’s look at the following example to get some real world numbers.

According to the U.S. Energy Information Administration, domestic hot water heating makes up approximately 17.7% of your home’s electricity consumption.

geothermal water heater

Source: eia.gov

So, if you spend on average $350 per month on your electricity bill, here’s how much of that is due to domestic hot water use:

$350 x 17.7% = $61.95/month

$61.95 x 12 months = $743.40/year

So if you install a geothermal heat pump, you’ll save between 50 and 60% on your domestic hot water costs. Let’s split the difference and estimate a 55% savings rate. That means you’ll save:

$61.95 x 55% = $34.07/month

$34.07 x 12 months = $408.87/year

That’s significant yearly savings on top of the 75% you could save on your heating bills. Geothermal heat pumps provide cost-effective heating and cooling, but their benefits go far beyond that. The desuperheater that comes with every Nordic heat pump is just one of the many pros of this innovative heating technology.

To learn how you can gain more than consistent heating and cooling with a geothermal heat pump, Download our Ebook.

Comments

  1. Reply

    Breck Lewis

    October 22, 2015

    That is really good to know that you can save that much money by going with the new heat pumps. People now days are all about saving money and having things done really fast. These new heat pumps gives you faster hot water and saves you so much. I just recently switch to this because I have a lot of kids and it seems like the hot water is always going out. How much does a standard geothermal heat pump cost?

    • Jordann Brown

      October 22, 2015

      Hi Breck,
      To find out how much a geothermal heat pump will cost for your home, use our Find a Dealer feature to contact a local installer and get an estimate.

  2. Reply

    Jenni

    January 29, 2016

    Hi Jordann Brown,

    Great one!
    I love this post of yours! Geothermal Water Heater is a money saver, specially those who has a big family. Now a days, saving money is a must. Very thankful that you’ve posted this. Off to share this information to my friends. Please post more.

  3. Reply

    Clifford Allen

    March 18, 2016

    I am a geothermal heat pump owner for 20 yrs now in Massachusetts. I have a 5 ton unit. My electric bills keep going up due to the utility rate increases. I somewhat agree with the desuperheater theory, but my question is, you are taking hot water~ 120 + degrees out of the water heater and pumping it to the desuperheater to somehow make it hotter and then get it back to the water heater at some increase in temp from when it left the waterheater. Even though my waterheater is plumbed with desuperheater per the schematic supplied it seems it would be more efficient it there was a separate tank hooked to the desuperheater that was then connected to the waterheater. Basically it would be a preheater. There must be some stratification of different temps in the waterheater and when the heatpump starts running you circulate this stratified water past the waterheater thermostat turning the waterheater elements on when they would not necessarily be running.

    • Jordann Brown

      March 21, 2016

      Hi Clifford,
      According to our manuals, we recommend using a domestic hot water preheat tank. For the pre-heat tank setup, the final tank should be set to 140°F(60°C), unless local code requires a higher setting. The pre-heat tank does not require electric elements. This setup takes full advantage of the desuperheater as it is the sole heat provider to the pre-heat tank. The desuperheater remains active during the compressor runtime until the pre-heat tank has been completely heated by the desuperheater alone. This setup is more energy efficient than a single tank setup.
      You can check out the diagram for this setup on page 9 of this manual: http://www.nordicghp.com/wp-content/uploads/2015/07/001200MAN-06-ISSUE-02-R-Series-Two-Stage-R410a.pdf

    • Joe Hohenfeld

      January 10, 2018

      I was told by my energy provider and installer the most heat to my water heater comes in the summer, when the by product (heat) is used to supply my water heater with warmer water. Can you help me with the conflicting information?

    • Jordann Brown

      January 10, 2018

      Hi Joe,
      With a heat pump, typical heating mode conditions involve a higher condensing temperature, e.g. 120F water or 95F air, so correspondingly higher compressor discharge gas temperature. In cooling mode, the condenser is the outdoor loop at 40-80F or outdoor air at 70-90F, so discharge temp is lower and there is less superheat to transfer to the domestic water.

  4. Reply

    Mike

    April 18, 2016

    If I turn off geothermal system still I am getting how water or not

    • Jordann Brown

      April 18, 2016

      Hi Mike,

      The desuperheater only runs when the compressor of the heat pump is running. If you shut the heat pump down the desuperheater won’t run and your regular hot water heater will take over.

  5. Reply

    cas browne

    September 10, 2016

    My Water Furnace brand geothermal says/shows in several different references to run the hot water from the desuperheater to the BOTTOM of the domestic water preheat tank and return to the furnace from the top. Your referenced diagram shows running the hot from the geothermal unit to the top of the tank and returning from the bottom. Can you explain this as I am getting ready to install a preheat tank and your advice seems more correct to me as a physics teacher.

    • Jordann Brown

      September 12, 2016

      Cas,

      Including the dashed line which is a dip tube included with the tank, our diagram shows the heat pump’s desuperheater returning water to and getting water from the bottom of the preheat tank. This way, the heat pump always gets the coolest water to heat, maximizing capacity. And cool water (which is not heated to the hottest temperature in one pass) is not returned to the top of the tank, where it would get sent to the electric top-up tank when anyone turns on a tap. The warmest water still migrates to the top of the tank by convection, where it continues to the electric tank.

  6. Reply

    Brian

    November 15, 2016

    I can see how this would be helpful when the geo is in the cooling mode, sending the heated water to the hot water heater or tank. But in the heat mode with well water being a constant 50 something degrees does it really make sense? Additionally is this beneficial when you have a propane hot water

    • Jordann Brown

      November 15, 2016

      Hi Brian,
      The desuperheater uses excess heat from the compressor operation, not heat that is extracted from the home in cooling mode or the ground loop in heating mode. Normally this heat would linger in the mechanical room, but we use it to preheat domestic hot water. This is free heat that is going to be produced either way, so you might as well use it to warm up your domestic hot water – even if you have a propane water heater.

  7. Reply

    Neil Frank

    January 21, 2017

    If I have a continuous flow hot water system with my current hot water heater how would that get connected to a geothermal hot water system? Thanks

    • Jordann Brown

      January 23, 2017

      Hi Neil,
      We need more information from you to answer this question. Could you send more details about your system to us through the contact page:http://www.nordicghp.com/contact-us/

  8. Reply

    Dale Rogan

    January 30, 2017

    Hello
    I’m a bit confused on my installation. My Geo unit showed the Cold Water Supply being teed off just before the cold inlet on the tank. The return from the Geo uint goes to the drain on the Tank. When the compressor is not running the supply to the Geo Unit is warm (about 74 F). When the compressor starts the supply line temp becomes tank temp and the return line is about 75F. I would think the return line should be around 130F. It seems I’m just pulling HW from the tank. I have traced the lines several times thinking something is not plumbed correct but they are as show on the diagram. Any comments would be appreciated. In this application of single tank, what should the lower and upper element temp be set to?

    • Jordann Brown

      February 03, 2017

      Hi Dale,

      We’d be happy to answer your questions, could you please email your questions to info@nordicghp.com? It would be helpful to include the model number and serial number of your heat pump.

  9. Reply

    Elaine

    February 06, 2017

    When we use our Waterfurnace Geothermal heat to heat the hot water, it always runs in stage two, the water gets too hot, and our electric bill goes up.

    • Jordann Brown

      February 06, 2017

      Hi Elaine,
      I’m not sure how the Waterfurnace unit is set up, but that won’t happen with our heat pumps.

  10. Reply

    Bud Kaczor

    February 16, 2017

    I have a 6 ton Bosch 2 years old. My domestic water is 140 in the summer and 120 in the winter. According to other sites it should be just the opposite. I replaced the 2 thermostats on the Marathon 85 gal tank and also replaced the pressure valve and expansion tank. Increasing the thermostats setting works for about a week and then returns to 120. Driving me nuts. Thanks in advance for any help.

    • Jordann Brown

      February 16, 2017

      Hi Bud,
      We do not manufacture the Bosch line of heat pumps, so cannot offer technical support on that product line.

  11. Reply

    Ron Housel

    August 06, 2017

    Jordann, I have a Geo Water Furnace closed heating unit with a desuperheater and a separate assist hot water tank. The service people found a leak in the coil and Freon gas has entered into our hot water domestic system. We have had thousands of small bubbles along with a medicinal-mineral oil odor and discolored water How did this happen? Unhealthy? Toxic?

  12. Reply

    love

    August 30, 2017

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    topic. You realize a whoⅼe lot its almost tougһ to
    argue with you (not that I really would want to…HaHa).

    You definitely put a fresh spin on a suЬјect that has been written about for decades.
    Ԝonderful stuff, just wonderful!

  13. Reply

    Joe Hohenfeld

    January 21, 2018

    Jordan,
    Thanks for the clarification on my last question. I’ve got another.
    I realize the best solution is a two tank system, however I can’t get my head around how the one tank system could have been working for me at all, over the past 25 years. Aren’t I “usually” circulating cooler desuperheater water in to my 120 degree water every time my geo system pump runs? I would expect the tank water is more often than not, hotter than DSH water. I’ve never really known if I saved any energy as it would be difficult to isolate the cost of hot water.

    • Jordann Brown

      January 22, 2018

      Hi Joe,
      We don’t recommend a one-tank system so can’t comment as to the efficiency of that setup.

  14. Reply

    Doug Snowball

    March 21, 2018

    Hello Sir;
    I have 2 Water Furnace units: 5 ton and 4 ton.
    Each desuperheater goes to a different 120 gal HWH. I would think both should go to a preheat tank and fill the supply tank?
    Your thoughts?

    • Jordann Brown

      March 29, 2018

      You can find plumbing diagrams for the desuperheater in our residential geothermal heat pump product manuals.

  15. Reply

    Hilton Electrical Perth

    April 09, 2018

    I love this post of yours! Geothermal Water Heater is a money saver, specially those who has a big family. Thank you so much for sharing these on the internet.

  16. Reply

    Jerry Cooper

    May 03, 2019

    We have a Hydron module geothermal he at pump system. Two water heaters. It has not supplied any heat to the first water heater for the last year. The pump for the dsuper heater was replaced. Pump ran so hot you could get burned touching it. Pipe gets warm 3 feet from the pump. I think pipe is blocked. Pipes on top of water heater are cold. These pipes used to get very warm. Jerry Cooper cooperjerry@hotmail.com (308)362-4339 We have been billed for over a $1,000 still no heat in the first tank.

    • Jordann Brown

      May 03, 2019

      Hi Jerry,
      Unfortunately, we can’t offer service on non-Nordic heat pumps.

  17. Reply

    John Simpson

    November 18, 2019

    So no water circulation takes place between the preheat tank and the superheater unless water is being used correct?
    I thought it circulated from the preheat tank through the water Furnance to keep the water warm all the time.

    • Jordann Brown

      November 19, 2019

      Hi John,
      The heat pump’s desuperheater only preheats your domestic hot water when it is running in space heating mode. The desuperheater does not do dedicated domestic hot water heating.

  18. Reply

    rachel frampton

    December 02, 2019

    I never knew that heat pumps reduces hot water cost. I’ve been spending way too much for my water heater and I have no idea how to reduce my water heater bill. Therefore I’m glad to know the benefits of heat pumping; I just have to look for an excellent service that can help me out.

  19. Reply

    Larry Hooks

    November 19, 2020

    What would be the best way to maximize your geothermal efficiency? Say that you want take a shower, bath, wash clothes or dishes? Should you turn on the heater or AC before your start? What is a good estimate of how long you should run the compressor if you use say 10 gallons of hot water?

    • Jordann Brown

      November 30, 2020

      Hi Larry,
      The best way to maximize your heat pump’s efficiency is to set it and forget it, requiring it to only come on when space heating is required. Intentionally manipulating the on/off of the heat pump is inherently inefficient and won’t save you money in the long run.

  20. Reply

    Fred

    March 05, 2021

    I moved into a house that has Geothermal heat/air almost 8 years ago. I have replaced my hot water heater 2 times so far and I hate doing that! Must a geothermal unit run off the hot water heater? Replacing is very annoying and I hate it! Very inconveniencing! Any tips to resolve this issue or will I need to replace the unit with something else, or just MOVE!

    • Jordann Brown

      March 05, 2021

      Hi Fred,
      Your geothermal heat pump should not be interacting with your hot water heater in a way that would cause it to need to be replaced. Is this a Nordic unit?

  21. Reply

    Suyog

    September 17, 2021

    Hi, thank you very much for the helpful article and the comment/ QnA section. I had a preheat tank that started leaking. So I discontinued it use. Is it safe to leave the DHM in and DHM out pipes disconnected and not having a functional preheat tank.
    I understand that the extra heat will go waste. But my question is if it is safe to do so?

    • Dan Rheault

      April 08, 2022

      Hi, sorry, Jordann departed and no one checked the blog for a long time!

      It is safe to not use the desuperheater, as long as you turn the ON/OFF switch OFF (if you have one), or disconnect the blue wire with the insulated terminal from the compressor contactor as shown on the electrical diagram stuck on the electrical box cover. That’s so the circulation pump doesn’t run without any water flow.

  22. Reply

    Derek Schildt

    February 13, 2022

    Just moved into a home with geothermal. It has been very cold since we moved here and we had no problems with hot water. In fact, it was very hot! The past couple days, it has been warmer and the geothermal unit hasn’t been running near as much. Now, it seems we just have warm water. Is this indicative of a hot water heater problem? Or is this just normal with a desuperheater?

    • Dan Rheault

      April 08, 2022

      Hi, sorry, Jordann departed and no one checked the blog for a long time!

      What you are experiencing sounds normal. A nice feature of the desuperheater is that it can heat domestic water right up to the plumbing code temperature of 140°F / 60°C. But it only does that when the heat pump is running for space heating or cooling purposes. So in shoulder seasons when the heat pump is running fewer hours, you will get less domestic water heat from the heat pump and will need to rely more on the final electric or gas water heater.

  23. Reply

    Colin

    March 07, 2022

    Built a new home last year and installed a Nordic 6 ton water to air geothermal which works great for heat and air conditioning. Also did the geothermal water tank additional 40gal to recover hot water which I get no hot water from. I basically have a 40 gal tank of cold water beside my hot water tank. This has been checked by installers a few times now and still don’t work. I am looking at installing elements in geothermal tank to heat water but is this necessary? Thanks for any info provided.

    • Dan Rheault

      April 08, 2022

      Hi, sorry, Jordann departed and no one checked the blog for a long time!

      If your desuperheater is not heating any water in your preheat tank, check that:
      1. The ON/OFF switch on exterior of the cabinet is in the ON position (“1” rather than “0”)
      2. The brown wire with the blue insulated terminal has been connected to the compressor contactor, as noted on the electrical box diagram on the electrical box cover. It ships disconnected in order to not cause the desuperheater circ pump to operate before the loop is filled with water and purged (which many people do after they first start up their heat pump).

  24. Reply

    Sohel'Rana

    October 31, 2023

    I appreciate your clear explanations and the emphasis on safety throughout the process.
    It’s evident that you care about your readers’ well-being and want us to tackle these issues safely and effectively.
    Your blog has become my go-to resource for appliance-related issues,
    and I’ll be sure to share it with friends and family who might face similar problems with their appliances.
    Keep up the fantastic work!

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