Instant Water Heater for Whole House

Ooops on 24/03/2024 - 11:02
Last edited 24/03/2024 - 12:23

Hi all,

Our current gas storage water heater is inside the house and I think it is time to change it to an electric one for multiple reasons.

We want to remove the storage component and go only with an instantaneous water heater, electric. We are in Victoria, eastern suburbs of Melbourne.

Questions for those who either have this setup or have experience in this field:

  1. We are on a single phase, do we need to move to 3 phases?
  2. Is an instantaneous hot water system available for the whole house?
  3. Would this setup work considering we never have 2 people shower simultaneously?
  4. Any trusted brands?

Any other thoughts or suggestions?

p.s. we asked ChatGPT, general copy/paste answers from the web. Nothing meaningful.

edit: Reasons for moving away from the existing system: The gas water storage system is in the middle of the house and not very efficient. We want to change it mostly because it is inside the house and there are risks concerning carbon monoxide and gas leaks. If the unit was outside, different story.

Home & Garden

Comments

  • Pcosmic on 24/03/2024 - 11:11

    Just leave till it breaks

    • Ooops on 24/03/2024 - 12:26
      +1

      If it breaks, we might have a problem (depending on how/what is breaks). That's because it is inside.

  • Overclocked91 on 24/03/2024 - 11:37

    What are the multiple reasons you want to change?

    • Ooops on 24/03/2024 - 12:19

      It is gas, inside the house, in the middle of the house. Not a good place if something goes wrong and has a gas leak or carbon monoxide leaks. Yes, we do have gas and monoxide carbon detectors but would like to move away from this system.

      If it was outside, different story.

      • Overclocked91 on 25/03/2024 - 21:04

        Ok, right. Do you have a gas stove? Moving the gas hot water outside is a good plan.

        • Ooops on 26/03/2024 - 12:52

          No, electric. Just water and ducted heating which we don't use anymore.

          • Overclocked91 on 26/03/2024 - 18:08

            @Ooops: Ok fair enough. Disconnect gas and organize heat pump storage hws.

  • SBOB on 24/03/2024 - 11:38
    +11

    Instantaneous electric is not common, especially for a whole house, for a reason.
    It's not generally practical in terms of heating capacity, nor cost effective due to electricity rates throughout the day, compared to something like a heat pump storage system

    • DoctorCalculon on 24/03/2024 - 22:54
      +5

      100% for heat pump HWS.
      For Victorians, there are three different rebates for conversion to a heat pump system: STCs + VEECs + SolarVIC $1K rebate (income tested).

  • brendanm on 24/03/2024 - 11:46
    +1

    Single phase electric instantaneous would be absolutely pathetic, if it exists.

    • sumyungguy on 24/03/2024 - 12:09

      I thought that too, perhaps not ideal for OP in Melbourne but for northern climates where the cold supply isn't so cold it could work. In the US they're called tankless and it's suggested they're more efficient than storage electric. Not what I thought so I'm heading off down this rabbit hole in perparation for an extra bathroom later this year.

      • SBOB on 24/03/2024 - 12:20
        +1

        Heat tank storage can be set to heat water during off peak or solar generation periods making the cost to heat that water significantly cheaper per kWh than instantaneous where use could occur during peak hours, if you're on the frequently more common tou plans.

        If you have solar, it's effectively the cost of your FIT rate (so ~5c/kWh, without solar off-peak may be ~15c/kWh) compared to peak rates which in some regions can be north of 50c/kWh

        If you're on flat rate obviously the maths is different

    • Ooops on 24/03/2024 - 12:20

      That's what I'm afraid.

      • sumyungguy on 24/03/2024 - 12:21

        For your climate you'll have to include 3-phase in your price comparison

      • brendanm on 24/03/2024 - 12:23

        Then why not just get storage hot water?

        • Ooops on 24/03/2024 - 12:25

          Not sure where to place it at this stage.

          • brendanm on 24/03/2024 - 13:04

            @Ooops: Where the gas one currently is.

            • thatonethere on 24/03/2024 - 13:26

              @brendanm: Assuming you can get the old and new out and in.

              I have two trapped dead hot water systems in my basement…

            • Ooops on 24/03/2024 - 17:13

              @brendanm: We'd rather use that space for something else than hot water storage. The gas duct heater is next to it as well which needs to go.

    • skillet on 25/03/2024 - 16:47

      The 2000W kettle for example….how long does it take to 50C? And how fast is your water flow?

      • Ooops on 27/03/2024 - 20:45

        True :(

  • Stewardo on 24/03/2024 - 11:46
    -2

    It depends on the size of the gas pipe going to existing machine.
    You can get bigger instant for more taps, allow around 9l per tap at once. ie rinnai 26 3 open hot taps
    Rinnai Bosch dux rheem

    • Muzeeb on 24/03/2024 - 12:13

      Did you read the post?

      • Stewardo on 24/03/2024 - 13:11
        +2

        Not very well

  • GordonD on 24/03/2024 - 12:16

    Saw instant heating taps being advertised. You just set the temperature you want on the tap, and the water comes out of that tap at temperature. Seemed like a great idea.

    Mentioned it here. Someone pointed out the bleeding obvious. That the amount of electricity that the wires can carry just doesn't contain enough energy to heat a lot of water to a very high temperature instantaneously. That's why gas is used for cooking and instantaneous water heating, because the amount of gas that can come down the gas pipe does.

    Maybe you could do a hot shower, or hot water out of a kitchen or bathroom tap, with a three phase supply and instantaneous water heater. But single phase wouldn't even come close.

    I'd be happy to have someone prove me wrong by pointing me at a product that could do it, because instantaneous electric would be great.

    • Ooops on 24/03/2024 - 12:26

      I think we need to factor in conversion to 3-phase for this reason.

  • boomramada on 24/03/2024 - 12:32
    +1

    Why don't you google for local electic hot water installer and ask all these questions, and while you at it, get a quotation?

    • Ooops on 24/03/2024 - 12:38

      Thought of that yesterday and,

      1. I don't want to waste anyone's time if there is any indication that I won't be able to do it
      2. I might have other questions after the conversation and this will help with that
      3. I can't place 100% trust in an answer from someone who has an incentive to sell you the thing you are asking about
    • Muzeeb on 24/03/2024 - 12:38
      +2

      Lol. Such a 2023 type question. It's 2024 dude.

      • Ooops on 24/03/2024 - 12:49

        Thanks! :))

      • boomramada on 24/03/2024 - 12:58
        +1

        Haha its still in fashion for 2050 at this rate, people scared of dealing with real ppl and rather ask some strangers in a forum. Almost feel like, I got a question, would you hold my hands while asking. Lol

  • saliya on 24/03/2024 - 13:17
    +1

    Depends on inlet temp. Melbourne average annual inlet temps are ~16C (61F) from https://water360.com.au/wp-content/uploads/2022/10/awa--wate… .

    This ( https://www.amazon.com.au/EcoSmart-ECO-11-Modulating-Technol… ) 13kW 240V system claims to be able to deliver 7.5L/min of 40C water from 62F input.

    It would be borderline on single phase IMHO:
    - 13kW @ 240V is 55A, if you have a 63A main breaker (common for single phase) you wouldn't want to turn on a space heater.
    - Shower flow in Australia is 9L/min (new build, older can be much more) not 7.5L/min
    - Average inlet 16C means at least some of the time the inlet temp is under 16C. The unit doesn't rate itself for shower flow at lower inlet temps.

    • Ooops on 24/03/2024 - 15:35

      Thank you for the answer. Got some good tips from this. +1

    • krisp on 24/03/2024 - 16:28

      40A is the new standard main house breaker in new estates.

  • altomic on 24/03/2024 - 16:33

    Why dont we use shower water heaters that are common in the UK?

    You can buy them for $100 on aliexpress.

    Cold water in , how water out, plug them into a power supply (away from water). Done.

    • SBOB on 24/03/2024 - 16:38

      Do the maths on the heating ability of 2400w from ambient to shower temperature,for a throughput of shower flow rate (eg 9l/min) and you might work out why

    • inertia8 on 28/03/2024 - 01:34

      Used them in Malaysia and they are what I would call muff garbage and this is with significantly warmer inlet temps…

      Hence the calls for storage or sticking with gas.

  • Euphemistic on 24/03/2024 - 18:04

    Why do you want instant electric?
    Whats wrong with electric stroage heater? Heat pumps are quite efficient and can heat the water when electricity is cheaper. Regular electric storage isnt very expensive eaither when off peak.

    • Ooops on 24/03/2024 - 20:12

      We haven't figured out yet where we can place the unit outside the home. At the moment is in the middle of the house.
      Plus, if we place it outside the home, it will require extra pipes and sh$t.

  • 2esc on 25/03/2024 - 10:45
    +1

    Heat pump placed outside near bathroom.

  • v8bargain on 25/03/2024 - 12:47

    In stead of one unit for central electric hot water system, I remember there's de-centralised approach where smaller instant hot water heating unit are installed closest to water faucet. Like under sink cabinet area.

    Benefits are:
    1. Closest to water faucet, minimal energy lost through pipe.
    2. Multiple units installation, bathroom hot water breaks down won't impact kitchen.
    3. You now have a new space for storage from where to old system removed.

    Drawbacks are:
    1. It gets tricky when space under sink is limited with power outlet, same goes for shower/bath area.
    2. You may not like dealing with mulitple units.
    3. This is more expensive.
    4. This could be uncommon in Australia (but I definitely recall seeing brochure from local supplier years ago)

    HTH.

    • v8bargain on 25/03/2024 - 12:49

      Something like this:
      https://www.stiebel-eltron.com.au/dem-6-mini-instantaneous-w…

      (I'm not affiliated with them)

    • SBOB on 25/03/2024 - 13:07

      heres an example product guide and when you look at the power/current draw/phase requirements, and you'll see why they are really impractical for use in a normal domestic home situation. You'd need to have some pretty unusual requirements where an instantaneous electric unit was the 'correct' choice drawing something 20+kw instantaneous at any time of the day (the power bills would be insane, let alone the electrical wiring and supply constraints) compared to something like a heat pump storage unit that draws ~500w and likely has a complete power draw for an entire day 2-3kw (possibly schedule in non expensive elec times)

      https://www.stiebel-eltron.com.au/download/STIEBEL-ELTRON-Pr…

  • LFO on 25/03/2024 - 13:28

    For instant hot water to perform efficiently it has to be very close to the taps/faucets.

    Otherwise we are talking about a very common electric hot water system.

    So, one instant hot water for the kitchen, two or more instant hot water on each bathroom (shower, sink/basin, bath tab), one instant hot water in the laundry and so on.
    A bit costly last time I evaluated it.

  • apolomka on 25/03/2024 - 18:14

    I've been using Steibel Eltron now for nearly 20 years and plumbers are always impressed with how accurate the temp is and how quick they are. They are great but I have 3 phase so don't know about single phase: https://www.stiebel-eltron.com.au/

    The bathroom is at the other end and other side of the house, so decided to get two, one 60 deg for the kitchen (outside) and one 55 deg for the bathroom (in wall cabinet), rather than take the pipes through the roof

    • Ooops on 26/03/2024 - 12:57

      I would love to have this setup.

  • harrywwc on 26/03/2024 - 07:20

    moved to an "instant heat" gas fired hot water system - love it! everyone (4 adults in house) has a hot shower, hot water for washing up, etc.

    to move to an 'all electric' version, we'd need to get 3-phase run to the house, and that's not an expense we can afford at this time.

  • xylarr on 26/03/2024 - 10:53

    You want to use the water tank as big battery. You charge the battery overnight (cheap rates) or on solar, and then use it for hot water. Also, as has been said, get a heat pump - much much more efficient.

    Heat pump plus solar is the way to go.

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