electric heat pump water heater

silvertop
silvertop Solar Expert Posts: 155 ✭✭✭✭✭
in Energy Use & Conservation #1
I was considering one of these electric heat pump water heaters,and was wondering if anyone is using one? I noticed the GE version requires a 30A breaker, I was trying to back down the breaker size, I am wondering if this is for cold weather backup? I am looking for an off grid solution and am trying to stay away from Propane. I have my present electric on a timer which works well, but still a power hog !
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: electric heat pump water heater

    Do you mean like the ones discussed in this thread: http://forum.solar-electric.com/showthread.php?t=9185 ?
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #3
    Re: electric heat pump water heater

    Hot water recovery heat pumps are really suited if you live in hot climate where A/C is used a lot, and is common. I don't think in temperate climates it makes sense if all you are going to do is heat water with it.

    Solar Guppy is the go to guy in my memory about water heat recovery heat pumps.

    Why not use preheat solar, into a demand? Why the aversion to Propane?

    Tony

    PS bottom line, is it is much more efficient to heat water directly from solar than from PV or other electric sources, to then convert to heat.

    T
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  • silvertop
    silvertop Solar Expert Posts: 155 ✭✭✭✭✭
    #4
    Re: electric heat pump water heater

    This sounds like it has definite possibilities! Wife likes the idea of dehumidify/cooling of the utility room in summer. Has anyone turned off the backup heating element or tried to run one of these on a timer?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #5
    Re: electric heat pump water heater

    They appear to have an interface for an external energy controller system (i.e., utility can turn off heavy loads)--However, that optional device appears to be present in one of the water heater manuals but seems to have disappeared from the GE website when I checked a month ago.

    There is the heat pump, plus backup electric heat for when the are gets too cold (around 55F or less???) and/or you have too much hot water demand and need to use the resistance heat as backup.

    I believe you can program to only use the heat pump (turn off big electric heaters)--but I would be surprised if you could put the water heater on a big electric timer that turned off all power from noon-6pm Monday through Friday (for example--that is my peak TOU in summer). I believe the water heater controller works better with 24x7 electric power.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • silvertop
    silvertop Solar Expert Posts: 155 ✭✭✭✭✭
    #6
    Re: electric heat pump water heater

    Wife told me preheat solar is not in the budget, collector space is also at a premium. I was just looking for a simple solution to conserve more. Propane price swings are crazy in NW WA. its like trading one evil for another. Timer is only on about 4 HR.a day this cuts the cost down but I was looking for more.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #7
    Re: electric heat pump water heater

    A Rinnai or Takagi demand propane will use ~ 140,000 BTU/hour going full bore. Depending on the flow rate, (a good shower head will reduce that to ~ 1/2).
    That translates to ~ 2 gallons of propane per hour, full bore. At five GPM, that is 300 gallons of hot water per hour! So an average 6 minute shower @ 2.5 gpm would burn 1/20 gallon of propane. At ~$3 per gallon, that makes that average shower (with the heater going full bore,, about $.15. Let's just say, adding in system loses, higher temp rise etc that that cost is $.30 at worst given todays energy cost.

    By contrast, a kwh of electricity has ~ 3400 BTUs. The same 6 minute shower would take ~ 8 kwh, at $.10 that works out to be ~ $.80 for the same shower! No matter how you cut it, that is the minimum of BTUs, add in system loses, overheating and recooling of water etc, and I bet you can round that up to $1. An electric demand or smaller storage tank can't change the initial equation.

    Just keeping it in perspective.

    Tony

    PS Someone might like to double check my math,,, as always.

    t
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  • silvertop
    silvertop Solar Expert Posts: 155 ✭✭✭✭✭
    #8
    Re: electric heat pump water heater

    Thanks Tony I had originally looked at tankless but was leary because of our low well psi. I just looked the Takagi and it has a min. of 15psi this has possibilities . It sure would be nice to remove a few Kw's
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  • XRinger
    XRinger Solar Expert Posts: 529 ✭✭✭
    #9
    Re: electric heat pump water heater

    Gas sure sounds good! My shower this morning is going to cost me $2.00.
    Since the oil burner runs on a 1/2 hour timer (once per day). :grr

    I'm thinking about a DIY hot water heat pump!
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #10
    Re: electric heat pump water heater

    Especially if you are on a well, be careful of dissolved minerals in your water. Those tankless systems get a high heat transfer by dividing up the water flow into tiny tubes - which can clog quickly when minerals are present. I was excited about getting a tankless a few years ago until I read that.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #11
    Re: electric heat pump water heater

    Even electric water heaters on with relatively soft water eventually clog up with mineral deposits... Eventually, these deposits collect around the elements and cause them to burn out.

    I take care of a small 4 unit complex with electric hot water--It is a race between fouling by mineral deposits vs failure from leaking. At this point, the heaters have mostly been failing from normal leaking after 10-15 years so I have not had to address the mineral issues.

    I too was looking at tankless natural gas heaters until I read about the "boiler" cleaning that a couple manufacturers recommended once per year. Did not want to go there.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • solarvic
    solarvic Solar Expert Posts: 1,071 ✭✭✭✭
    #12
    Re: electric heat pump water heater

    My GE geospring has used about 270 KWH of electric since 0ct 15 last year. I think it needs power 24/7 for the control to work but not sure. When I started it it did a cycle to make sure the heating element worked and never has come on again as I use the energy saving mode. I have had some poweroutages that lasted 10 hours and the heating elements never come on so maybe it is possible to turn off the electric for awhile but I am not going to. I really like mine so far. :Dsolarvic
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  • silvertop
    silvertop Solar Expert Posts: 155 ✭✭✭✭✭
    #13
    Re: electric heat pump water heater

    Now Im not sure what the best sys. would be. Im going to let this sit before jumping . I sure would like to cut more Kws..............
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #14
    Re: electric heat pump water heater

    How hard is your well water? If it is fairly soft, a tankless propane hot water heater may still be OK.

    Tony/Icarus takes care of a few different cabins in his area with tankless hot water heaters--As far as I know, he likes them very well.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • SteveK
    SteveK Solar Expert Posts: 387 ✭✭
    #15
    Re: electric heat pump water heater

    Here is what I do. I built an insulated mechanical room to house the solar, washer/dryer, water heater and chest freezer. I vent the colder air through the wall into the uninsulated portion of the basement. The mechanical room stay ~56F and the rest of the basement gets down to 50F.

    The Nyle Northroads Geyser is the only setup that you can effectively duct the inlet/outlet air to seperate enviroments. Very handy and it's a real asset to us.

    We remove 5 gallons/week of condensate from the basement air. Remember that every gallon is equal to 1KW of energy saved...this in addition to the simple COP savings. The water removed is distilled...

    The Geyser is also the only setup that busts up the stratification in the tank allowing you to have a full 50 gal of hot water. The Geyser has an industrial pump that circulates and samples the water temp from the bottom of the tank and will cycle off/on according to it's temperature sampled.

    Nyle specializes in lumber drying, very large piles of it, the geyser has a bigger brother too.

    It is a rugged product with an industrial look/feel (very weighty). I got mine for $900 and the hookup took all of ten minutes...

    Oh I forgot, in the worst months of the year where the basement is coldest we spend $15 a month on hot water. This using it for dishwasher and washing for four. I can drive this easily with the Exceltech XP1100 inverter.
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  • System2
    System2 Posts: 6,290 admin
    #16
    Re: electric heat pump water heater

    Solar Hot water system in homes can save a large portion of your energy bills.
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #17
    Re: electric heat pump water heater
    edwardsmith wrote: »
    Solar Hot water system in homes can save a large portion of your energy bills.
    I think my Gas company figured that out to. They give you the gas almost free and charge a minimum Service Charge fee of $15.00 a month.
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  • XRinger
    XRinger Solar Expert Posts: 529 ✭✭✭
    #18
    Re: electric heat pump water heater
    Blackcherry04 wrote: »
    I think my Gas company figured that out to. They give you the gas almost free and charge a minimum Service Charge fee of $15.00 a month.

    Reminds me of our electric bill.. I think the KWH cost is about 11 cents..
    But after all the add-ons & taxes & payoffs it's 21 cents per KWH..

    Because CO2 is so deadly, some day soon, I expect we'll see 50 to 90 cents
    per KWH, but the bill will still say 11 cents per KWH.. :roll:


    I've got the old Sanyo unit ready to repair. (It can do 36,000 BTUh in heat mode)
    It would be really nice, if I can rig it to make hot water.. Save big bucks on oil..
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