Heat Pump water heaters

Discussion in 'General Discussions' started by Palace GeoThermal, Mar 3, 2015.

  1. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Any good recommendations for Heat Pump Water Heaters?
  2. pfer10

    pfer10 Member

    If you're going to buy bigger than 55 gallons and don't want a heat pump version you better buy before April 15. All DWH above 55 gallons will need efficiency of 2.0 or greater then. I think the rule was passed back in 2010.

    I think AO Smith and GE seem to be the leaders but I haven't paid much attention to it for several years now. My last house I ended up with a tankless NG but then ended up moving a couple years later.

    I am also interested again in any responses to this thread as the new house has an old electric that I am sure is on it's last leg. I know my basement stays ~58F in winter and ~62F in summer. I would have to do some checking to see how they perform in those conditions. Seems like they are best in nice warm garages down south. Also I know complaints are they are significantly louder than your refrigerator.
  3. pfer10

    pfer10 Member

    It looks like the Stiebel Eltron gets high marks but also a high price tag. It seems to be the only now calling itself a "non" hybrid. http://www.stiebel-eltron-usa.com/accelera.html The new 58 gallon model should be out now it looks like.

    Only document I really could find on COP and surrounding temp:
    Screenshot 2015-03-03 at 8.07.19 PM.png
  4. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    I still cannot make much sense (up north) out of the idea that you heat up the thermal envelope, which includes the basement, only to take the heat out again. Certainly more appropriate in the south. DSH (for <55 gallons) and dedicated w-w geo heatpump (for >55 gallon) make more sense to me.
  5. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    We did the math once upon a time and it did favor the HP water heaters in my AO, but the advantages are obviously in warmer climates.
  6. ChrisJ

    ChrisJ Active Member Forum Leader

    I put one in at the end of December. I have radiant heat in the basement supplied by the GSHP.

    The HPHW definitely makes the basement zone turn on more often to keep it at 65* air temp. I believe it is still a net savings over running a straight electric water heater. I don't have a DSH.

    It is the GE Geospring.

    Last edited: Mar 23, 2015
  7. mtrentw

    mtrentw Active Member Industry Professional Forum Leader

    It will certainly make more sense in a cooling dominated climate or an area that needs dehumidification. But it still can be an energy positive in heating dominated. With some very basic assumptions and basic math.
    HPWH COP = 2.0
    GSHP COP = 3.0

    I need 6 units of hot water.
    HPWH uses 6/2=3 units electric to get there while grabbing an additional 3 units of heat from within the envelope.
    GSHP uses 3/3=1 unit of electric to get the 3 units of heat back into the envelope.

    I used 4 units of electric to get 6 units of hot water, which looks like a net COP of 1.5 to me.

    While it'd be better still to get the hot water at the GSHP COP through DSH or dedicated HW, that strategy is more suited for the design phase. Retrofits of existing DWH can work in most climates. Just takes a bit of math to determine if the financials support it.

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