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Need for hot water?

  • 07-08-2022 9:03am
    Registered Users Posts: 195 ✭✭

    Reading through information on heat pumps and solar panels, I keep end up back at the same point and the advice that,

    "you will need a device to generate hot water" - I understand heat pumps and solar panels can be used for this....

    But my question is why do I need hot water? I have an electric shower, dishwasher, washing machine. I can't say I ever use the hot water that is generated currently by the oil central heating. Only reason I can think of is for a bath, but hardly worth a keeping a tank of hot water for something I never use.

    What am I missing?


  • Registered Users Posts: 10,230 ✭✭✭✭the_amazing_raisin

    You say you don't need something to generate hot water and then mentioned 3 appliances that heat water 😉

    I'm guessing it's more around the need to store hot water. When it comes to having Solar, the logic is the same behind a battery, it allows you to store energy for later usage

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost (Escapist magazine)

  • Subscribers Posts: 39,907 ✭✭✭✭sydthebeat

    Each of those appliances are using an electric element to heat water.

    Each of those appliances is less efficient currently at heating water than your oil system.

    A heat pump will do this for you at better efficiencies

  • Moderators, Education Moderators, Home & Garden Moderators Posts: 7,919 Mod ✭✭✭✭Jonathan

    The 9kW instantaneous electric shower is your problem. No domestic solar system is going to be able to keep up and supply it with enough power when you need it most (morning and evenings).

    Most of us here have a cylinder for storing water which we heat from solar slowly over the course of the day (from Solar thermal, solar PV, heat pump) and then use it when we need it using a pumped shower.

  • Moderators, Home & Garden Moderators Posts: 4,996 Mod ✭✭✭✭graememk

    Although, all bar the shower only use cold water. so that point is moot for them devices.

    But as Jonathan said, The hot water tank can run your showers by heating it slowly, thoughout the day. And I like having hot water come out of the tap. Its one of the nice things in life. I dont wash many dishes, nearly everything goes into the dishwasher, straight from the table. but the baking trays and stuff that isnt suitable, hot water is a lot easier than cold to wash them in.

  • Registered Users Posts: 10,230 ✭✭✭✭the_amazing_raisin

    I was actually impressed recently to find that my dishwasher says you can hook it up to the hot water supply instead of you want

    I've seen washing machines with hot feeds are making a bit of a comeback, unfortunately it tends to be the most expensive models, so what your save on water you spend on the appliance

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost (Escapist magazine)

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  • Registered Users Posts: 2,269 ✭✭✭bullit_dodger

    Just to expand a little on what raisin mentions, heating water is the single biggest energy usage in your average house. Infra-red panels aside, heating invariably is done via radiators (hot water). Washing clothes and dish washing again the same. Tumble drying the same albeit your trying to remove the water by evaporation.

    I'm a little like you. I've an electric shower, but a useful thing that you can do with your immersion tank is heat that with free solar energy, then install a pump and take your showers from the immersion tank. In ireland we've got basically two model electric shower. Triton/Mira and those Triton T90's rock in at 9Kw an hour on the 2 bars!! At today price of €0.30/unit, that's €2.70 an hour. So a 10 min shower is €0.45! you have a couple of people taking showers a day that rocks up pretty quickly. If you can solve that via free solar, you can save yourself a few quid a day (just on showers)

    Edit: And just noticed that the lads have said the same things above - but when I started writing I was comment #3 :-)

  • Registered Users Posts: 1,230 ✭✭✭DC999

    I'd agree with @DaveR1 but after I looked it a lot. Thougg thay said heating water is a huge % of our electricity bill. So deffo makes sense to review what you spend heating water and see what works for ye.

    If we were in a newer house with insulated tank, insulated pipes... if money was no object, if would be a different decision though and would make more sense.

    I was getting a new hot water tank and Eddi diverted with the new solar but cancelled it when decent FIT was announced. Was gonna cost about a grand for 2nd hand insulated tank (180l) so not huge and not great insulation (supply and fit) and then needed a new pumped shower.

    We don't have a bath in the house. Have an electricity shower so use it to heat water on demand. Any water tank losses heat that you've paid to heat. Great tank insulation helps but costs a lot for newer very efficient tanks (supply and install). And ours is our bedroom and we don't have space to move elsewhere. So in summer (when weather is warm) it would likely leak enough heat we may have to turn it off. As our room would be too hot at night.

    Then have to swap power shower for one pumped from hotwater tank.. So buy it and get fitted and run pipes from tank to shower.

    Some dishwashers and washing machine can only have 1 intake (our 2010 dishwasher has one) so cant take hot and cold. So if you take 70c water from tank to a washing machine for a 20c wash, you'll shrink your clothes..

    More likely the hot water would never make it to the device due to length of uninsulated pipe in our house from hot water tank to machine. Our dishwasher takes very little water on on 50c 'eco' mode and sloshes it around for ages. Uses 1.1kwh taking in the cold feed. So connecting to a hot feed we'd only save a % of that 1.1kwh that is used to heat water. But if I use the 70c mode if goes to 2.1kwh. So turn the temp down will save nearly half the power.

    Using our shower on eco mode uses close to have the power when on high. And is a better temp for 2 of 4 of us in the house. Electric showers uses way less water. About 6 liters a min v up to 20 on pumped shower. So that's a lot of lost water (environmentally) and lost energy you paid for to heat it. Or you get a water limiter on the hose of course.

    Solar PV is less efficient for heating water than solar thermal. So I am better get money back from FIT or maybe buying a battery. And excess goes into my ev which I will us, versus water heat I might use (but cools with heat losses).

    My father in law takes a 20min shower every day and his electricity bills are scary. Or a house with teens who like in the shower would be a different scenario.. But they are not our usage..

    Long post and in an ideal world I would have hot water. I am deffo all about reducing the energy usage and waste. But doesn't work for us in this 80 year old small city-house now where there are other energy 'leaks' to tackle. But water heating is deffo a good debate to have

  • Subscribers Posts: 39,907 ✭✭✭✭sydthebeat

    What do you mean "use cold water"?

    .. Each of the appliances mentioned generate hot water from the cold feed, through electric element heating. You do not wash dishes or clothes in cold water.

    Yes you can purchase appliances that have a hot feed to make the appliances more efficient, and thus use renewables sources for hot water, but these tend to be the more expensive appliance... And also need to use the element when certain temps need to be reached, not least legionnaires clearing cycles

  • Moderators, Home & Garden Moderators Posts: 4,996 Mod ✭✭✭✭graememk

    What I mean is on most washing machines they only took a cold water supply only, Not hot water from a tank.

    No option of a hot supply. I do have a hot supply beside the washing machine in case any future machine supports it.

    Although it was 8 yrs ago when we were getting new washing machine and dishwasher and having a hot supply were non existent, Its good to know that they are making a come back.

    Must dig out the manual for my dishwasher.. Its right beside the sink so getting a hot supply to it would be quite easy.

    On a side note, If your air drying clothes in the house, Get a dehumidifier, Dries the clothes much faster than even putting them direct on the radiator.

  • Registered Users Posts: 2,717 ✭✭✭yankinlk

    I read an article a while back that all detergents these days wash very effectively without hot water. They are designed to perform better in colder conditions. All my machines have energy saving settings and we use them all the time. The one electric shower is for emergencies only...habits are hard to break but are worth it.

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  • Registered Users Posts: 5,867 ✭✭✭SouthWesterly

    What would it cost to get a pump shower in?

    I've a 300l cylinder in the attic.

  • Registered Users Posts: 10,230 ✭✭✭✭the_amazing_raisin

    You can get a booster pump attached to the output of the tank, so you can keep your normal showers

    I've a 2 outlet grundfos one in the hot press's beside the tank, connected to both hot and cold feeds

    Pressure to the shower and bath is great, but they do tear through the water pretty quickly. I think I've a 230l tank and we've really only enough water for 2 showers for the grown ups in the morning and 2 baths for the kids in the evening, after the tanks have refilled

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost (Escapist magazine)

  • Registered Users Posts: 5,867 ✭✭✭SouthWesterly


    My thoughts are to bring the pipes down from the cylinder in the attic and keep the electric shower as well.

    It's next years project along with increasing my panel count.

    A friend with the same size system as me got an eddi today so I'll see how effective it is over the next 6 to 12 months