New House: Should We Do Heatpump HWC or Panel Type or Traditional? Also - Indoor HWC Vs Outdoor HWC

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  Wakrak on 02/10/2024 - 12:53

  Might be worth posting on Geekzone too

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    mickey9876 on 02/10/2024 - 15:04

    I'll do a search first and see if there is already something there before posting!

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  FiveFeetUnder on 02/10/2024 - 13:47

  Heat Pump hot water won't pay for itself with savings over 5yrs (due to the much higher price), more like 8-10yrs when I last looked.

  We ended up going for a standard mains pressure electric HWC with dual elements, and then hooked the bottom element up to a timer to run on the Contact 3hrs of Free Power each night from 9-midnight. This saves us 3kwh x 3hrs per night, which is like $700 per year

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    mickey9876 on 02/10/2024 - 15:05

    Interesting as from my limited research, it says HeatPump-HWC saves 50-75% of the traditional HWC cost. And if we assume 30-50% of power costs is from HWC, wouldn't this savings be much higher?

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    desikiwi on 03/10/2024 - 11:35

    1 years or less for me then free ish unlimited hot water when I get pv as base load for hwhp is only 800watts and 11kw pv array even on cloudy day will put out close to over 1kw which is enough for heating water .

    External hot water cylinder is 1800 approx new i got my midea one for 2.5 k i app run it only from 10 am to 8pm every day to 55 c with disinfectanting run every Saturday.

    External cylinder frees up space , in my small house i also changed my entire plumbing of house .

    Acop for midea is over 3 I find visible difference in power consumption by a third as well .

    285 liter is enough for my 2kids and 2adults to have comfortable shower .

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      FiveFeetUnder on 03/10/2024 - 12:35

      If you have solar PV, then why would you get a heat pump cylinder over a normal electric cylinder, with the solar heating up the cylinder each day? Save the extra cost of a more expensive cylinder because the power is free anyway?

      Edit: note that the Midea Heat Pump HWC has a 5yr warranty on the cylinder and 3yrs on the compressor, where as the Rheem/Rinnai electric cylinders have a warranty of 10-12yrs on the cylinder.

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        desikiwi on 03/10/2024 - 14:20

        Midea will not be that great with warranty support as well compared to rhreem for me cost was big factor so that is why midea and lowest possible energy costs , with solar pv i think using hot water heatpump cheap one like midea is just better use of power in summer i think I may get ev or phev i would prefer to dump excess power in car then my hot water cylinder,

        I think my roi for hwhp is around a year so it's kind of cheap, for rheem it would had been 4 years i think roughly

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  tomb98 on 02/10/2024 - 16:48

  The issue with heat pump HWC is that they cost around $7-8k to install vs $1-2k for a traditional. The rated lifespan of them are about the same (10-15 years), though I suspect they can go a lot further. So the question really is if you think you'll save at least $1000 a year in hot water electricity over conventional. Personally, having a heat pump HWC installed myself and going from a traditional HWC, I can say the savings are somewhat exaggerated. I think optimistically, I'm maybe saving about 20% using the heat pump one at most? Also, the heat loss and running cost even if you don't use the cylinder much is quite large. On a 300L cylinder, I use about 10-15kw (at least) per day even with minimal use.

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  mickey9876 on 02/10/2024 - 21:26

  So this page is good but only compares heat pump HWC to gas. I wonder how it compares to traditional HWC- https://genless.govt.nz/for-everyone/at-home/energy-saving-a…

  https://www.consumer.org.nz/articles/home-heating-costs -
  This page says gas is much cheaper to install and provides almost same savings as Heatpump HWC but the risk is in the coming years gas might increase in price a lot- I wonder if that cost increase will be in the next 5 years where gas will cost the same as electric HWC?

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    mickey9876 on 03/10/2024 - 10:19

    Actually, natural gas isn't available in South Island which rules the gas out and LPG apparently works out more expensive than electric!
    So either traditional HWC indoor(to ensure no heat loss to the -ve temperatures of south island winters) or outdoor heatpump hWC if living in the house for 10+ years :(

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  desikiwi on 03/10/2024 - 12:00

  I am at hornby Christchurch i renovated my house with hot water heat pump and heat pumps through the house , for dryer i also have a heat pump dryer and a regular all in one washer dryer . Heated towel rails on wifi timmer to turn on in evening and on entire night and week ends , my toilet bidet seat is also kept warm with heating on always , which also sprays warm water 💦 , i some times also keep heated lights in bathroom on . I consumed about 60 kw max a day with most of the days on 45 kw

  when I was renting my power consumption of keeping two rooms warm + lounge warm i consumed about 90kw a day, a house with cold kitchen toilets passage bathroom laundry etc . Not a good feeling need to wear warm cloths in the house .

  You can buy external hwhp midea for 2.5 k Christchurch,trade depot, 4ish k my plumber can get rheem hwhp . Haier is mono block type with very high heat storage capacity with pv energy storage ie it will dump excess solar as convection heating of water to 65 c i think

  Hwhp is not good if you will consume a lot of hot water continually then you have to get gas .

  Hwhp are slow at heating water i think 6 hours for mine .

  It makes some sound outside and fans move air .

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    mickey9876 on 03/10/2024 - 12:52

    Thanks - what is your heatpump set up in the house? All rooms have separate units or multi split units? Just trying to understand the 45KW usage when you mentioned 'heatpumps throughout the house". THanks

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      desikiwi on 03/10/2024 - 14:09

      Midea mini splits not multi split more like back to back with very little complexity, they peak 400 watts but they are all dc inverter so I think it's 4 stage compressor 2.0 kw infinity air series for 3bed rooms , 7kw heat split in lounge house is roughly 110sq meters continuous .

      I was answering some of your questions on the other forum topic .

      As per my power company, consumption changes with outdoor temperature but on average it was around 45 kw we use hot plate for cooking also make bread at home , steam banking so on

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  scott on 06/10/2024 - 00:10

  There is a big tread on geekzone where similar stuff was discussed a week or so ago.

  The subject of that thread was on one of those 3 free hours of power a day power plans, so the logical solution for them was to go for a really big (ultimately they went with a 300L even though a 400L was suggested) conventional cylinder, with top & bottom elements. Bottom element gets wired to a timer to run for the three free hours a day, and top element gets 24/7 power to keep a small amount of hot water available at all times. (and one likely the bottomed gets controlled power so you get the cheaper controlled power rate)

  This setup is also great in terms of future proofing for solar PV. Either swap out the timer for a solar diverter, or just program the timer to run at peak solar hours…

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  Generally solar thermal setups have gone out of fashion these days. Never really looked into it too much, but I guess that the cost of solar PV has dropped to a point where that is the better option.

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  On hot water heat pumps. Save 1/3rd of your power, but only expect them to last 5 - 15 year's. (our conventional cylinder is still going strong in our 30 year old house for comparison). If you are not planning PV in the future (and don't have a power plan with cheap off-peak hours), they likely stack up.

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  On indoors vs outdoors, both conventional and heat pump cylinders come in both flavors (with an outdoor box for the indoor cylinder heat pump setup). Advantage of the indoors setup is the ~1.5 kWh / day of waste heat goes into keeping the house warm (ideally the linen cupboard), and the cylinder may last a bit longer out of the weather. Advantage of outdoors is that indoor space is freaking expensive, and you free some up by not having the cylinder.

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  Consider location of the cylinder carefully. You really want it close to water use locations. Every bit of water you run down the drain waiting for hot to arrive is waste, and is directly related to the length of pipe run. (can get a loop system to avoid this waste, but that does cost more and use more energy).

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  Myself right now, I would likely go for a 300 or 400L twin element system with a solar PV setup. It is going to be a lot more cost effective to install solar PV on a new home than it is as a retrofit later.

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  General new home notes:

  • Try get a high capacity electrical connection. Either 100A single phase or ideally 100A three phase. The standard 60A single phase connection is a bit lean when talking about all electric homes, induction cooktops and EV's.
  • Get an induction cooktop. Well worth the extra money.
  • Get the expel air one width bigger than the cooktop.
  • If you are able to get Cat6 data cables run while the walls are open (an easy DIY job if you are up to it), it is far easier than retrofitting)
  • Make sure the circuit board has lots of free bays
  • Try to get conduit (or cable good for 32A (3 phase if you have it)), run from the circuit board to each probable EV charging location for the future. No need to terminate it at this stage (unless you have an EV).
  • I rate having some outdoor power socket's
  • Much easier to sort out the heating / cooling solution at new build stage, than it is to retrofit it later.