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Tankless Water Heating and Geothermal? The Perfect Match

Posted by Jay Egg

Dec 23, 2015 5:40:00 AM

Combining these time-tested technologies can be a big energy saver.

Geothermal and Tankless Hot Water Schematic

HAVING A 50 OR 80 GALLON TANK HOT, full and waiting to provide domestic hot water (DHW) for household needs has been the norm for quite some time. Of course, we have to “suffer” through those 30 seconds or so of cold water, but we learned to deal with it.

Enter in the “tankless” water heating revolution.  Brilliant, because we no longer waste the energy of keeping a dormant tank “hot” for hours on end, and the real bonus is that we no longer have to “wait” for the hot water to hit the shower head or the faucet. Let’s get back to that tank idea; someone decided that if we put a non-heated holding tank somewhere in the conditioned space, it would “pre-heat” the water to at least 70F. That’s a lot better that 40F or 50F, right?  Another great idea.

Is there a way to get that holding tank even hotter without using more energy?  There sure is, and you probably already guessed that you can do it effectively with a geothermal heat pump (GHP).

With a GHP, you can get a factory installed Domestic Hot Water Generator (DHW Generator), or as the techies call it, a “desuperheater”. In the cooling mode, the GHP is taking heat out of the house and returning it to the cooler earth.  By passing this extra heat off to the DHW circuit in the GHP, you get “free” hot water.

When you’re into the heating season, the heat is not quite free, rather it costs only about 20% of what an electric or even a gas heater may cost to do the same amount of heating.  Who wouldn’t sign up for that?

Vintage Tankless AdGHPs with DHW generators typically don’t run on demand for hot water needs, meaning they don’t cycle on every time the temperature in the tank goes below a set-point.  They operate as needed for cooling or heating the house, supplementing you with free or nearly-free hot water as they heat and cool your home or business.  Unless you find yourself in what is referred to as “swing-time” (no heating or cooling needed), you can bet you’ll pretty much always have a supplemental DHW supply.

So there you have it, another great benefit you too can have when you “Get Ready to Geo

geo_FamilyThere are many ways to apply geothermal HVAC systems to your project.  Whether it's 3 tons or 3000 tons, pool heating or radiant in-floor, geothermal provides the prefect answer.  Geothermalsystems are the Masterpieces of Heating and Cooling.  

Geothermal Case Studies


Jay Egg is a geothermal consultant, writer, and the owner of EggGeothermal. He has co-authored two textbooks on geothermal HVAC systems published by McGraw-Hill Professional. He can be reached at jayegg.geo@gmail.com   

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