Home Forums General Discussion On demand electric hot water for kitchen use

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  • #1619

    Hi – wondering if I can tap into some of the wisdom of this group please.

    I have been asked about using on demand electric hot water in a kitchen.

    There is currently a small electric cylinder in the kitchen (downstairs) and a larger electric cylinder upstairs (a long way from the kitchen) and the kitchen is being remodeled. The owners would rather not have another cylinder downstairs and the people putting in the kitchen have advised on demand hot water in the kitchen. There is gas in the street but this is not connected, and they are not planning on using gas for anything else. So we’re currently discounting gas as an option (unless anyone tells me otherwise).

    I’ve seen various bit of advice that tell me on demand electric is expensive to run and due to the large power demands, and may require a cabling upgrade (although they’ve been told by the kitchen installer this wouldn’t be required – I’ve suggested checking with the electricity retailer). However, its suggested that is could be a good solution in situations where the supply is a long way from the main cylinder (which it is) and heating demands are low (e.g. a handbasin).

    So… what is the approximate power output required for an on demand electric system sized for a kitchen? And on average what volume of hot water would be required for a three person family. I’ve tried to hunt for this but can’t find it.

    Basically, would anyone recommend on demand electric in a kitchen?

    And if the running costs of electric on demand are prohibitive. What are the other workable options? I presume replacing the small cylinder in the kitchen??

    Thanks

    Sally

     

     

     

    #1621
    Christian Hoerning
    Participant

    Hi Sally,

    Here are my thoughts:

    Continuous flow electric hot water heating for a remote kitchen sink is one of the few applications which I would recommend. I don’t know much about the sizing and would leave this to the supplier to work out but basically unlike for showers and baths you don’t require a high flow rate in the kitchen so there should be a system small enough in terms of power rating to work within the capacity of the existing electric wiring.

    Also, I wouldn’t be too concerned about running costs either. First of all, this really is only an issue for the household if they have separate meters for controlled and uncontrolled electricity supply with different prices for each. If it is only one meter the pricing would be the same as with a ripple-controlled cylinder. Furthermore you avoid standing losses from the cylinder in the kitchen which should at least offset any additional running cost if you had to pay a higher price for uncontrolled electric water heating in the kitchen.

    It is true that uncontrolled electric water heating poses a higher strain on the electricity supply system as it adds to peak load. However, if we are only talking 20 litres or so per day to wash the dishes etc. I wouldn’t worry about this. Many dishwashers heat their own hot water anyway which basically is uncontrolled electric water heating, so this wouldn’t change.

    So if it was my house I would definitely consider continuous flow electric water heating for a remote kitchen sink and simply compare the upfront costs of a) connecting to the main cylinder, b) replacing the small kitchen cylinder and c) the continuous flow system. I wouldn’t worry about anything else really.

    Cheers, Christian

    #1622

    Thanks very much Christian, that’s a useful steer.

    The only part of your post I don’t fully understand is this comment below about running costs:

    First of all, this really is only an issue for the household if they have separate meters for controlled and uncontrolled electricity supply with different prices for each. If it is only one meter the pricing would be the same as with a ripple-controlled cylinder

    This is due to my lack of knowledge about controlled and uncontrolled supply. Are you saying that if they are using an uncontrolled meter for continuous flow water heating in the kitchen it will be more expensive (i.e. because uncontrolled supply is more expensive), whereas one meter on a controlled cylinder would have lower costs? Does this also presuppose that if they only have one meter it will be a controlled supply?

    I could just call you to ask you about this… but if you can bear explaining it in writing then someone else might learn from it too : )

    Thanks very much.

     

    #1623
    Christian Hoerning
    Participant

    Alright: The continuous flow electric water heater should use less electricity (kWh) than an electric cylinder for providing the same amount of hot water. This is because there are no standing losses. However, as no hot water is stored it needs to be on an uncontrolled electricity supply.

    If your uncontrolled electricity supply is metered and charged separately at a higher rate than the controlled supply then it could be that the total cost for hot water is higher, depending on the amount of hot water used. If you use only small amounts of hot water then it could be that the higher electricity cost and the savings from not having standing losses cancel each other more or less out.

    Some households only have one meter and hence pay the same rate for their controlled and uncontrolled electricity usage, based on a generically estimated split between the two. Some households have two meters but only get charged a single rate for everything. In these cases the only thing that would make a difference in the running cost would be the standing losses you would have with a cylinder but not with a continuous flow system (assuming the same hot water usage).

    #1624

    Thanks very much Christian!

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