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Help with heating options and costs

Discussion in 'Plumbing and Central Heating' started by mansea, 12 Jun 2021.

  1. mansea


    20 Nov 2019
    Thanks Received:
    United Kingdom
    Is anyone able to help with approx heating cost calcs please? (Kw)

    I am looking at 2 options as am completely off grid, don't want oil or lpg gas, so leaves electric only. Don't really want ashp. So my options really are upgrading night storage and immersion heater (currently installed) or installing electric combi boiler and wet central heating, I think this is my preferred option, but Id like confirmation that the cost savings in running (if any) are worth making the change.

    So the calc would be 1x combi boiler firing as necessary for heating/hot water, i predict approx 4-6 hours on use per day in the winter, no idea of wattage as its regulating, I believe around 0-14kw with single phase. So maybe 14kw getting heating up to temp then ticking over on 0-2kw to maintain desired temp.

    And currently there is immersion heater (no idea of wattage), 4x 3 element night storage heaters (believe each element is around 750w?) These are currently running off peak on econ7 tariff, so on for 7 hours per day. And a 2kw heater in bathroom for blast of heat on demand, maybe 30mins-1hr use per day. I should add as well that occasionally this system has to be topped up with on demand electric to boost room temps to desired level.

    Should add there is an electric shower for daily use, which will be staying and not effect calcs/demand, so immersion and combi would only have to heat water at 3 taps (plus addition of wet radiators for the combi).

    I am thinking if I go the electric combi route there are potentially cost savings, plus increased comfort levels and convenience of instant hot water on demand and being able to get rid of the immersion tank and update the controls with room stat and trvs etc. Is anyone able to help/confirm with the kw calcs please?

    Also does anyone know the effect on the epc with night storage vs electric combi boiler? Would one likely be more favorable? I would assume the electric combi due to room stat and trv controls. Is it calculated on total kw usage or on assumed econess of the system? Ie extra brownie points for systems that make use of renewable energy/solar etc.

    Thanks in advance!!
    Last edited: 12 Jun 2021
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  3. flameport


    10 Mar 2007
    Thanks Received:
    Poole, Dorset
    United Kingdom
    Forget about electric combi boilers. Will cost an absolute fortune to run, hot water performance will be useless, and any EPC rating will be straight in the toilet.

    None of those things will happen.

    Using peak rate electricity for heating instead of E7 for the storage heaters will cost between 2x - 4x more.
    A single phase combi is limited to about 12kW, which being generous with the incoming and outgoing water temperature will be a trickling 5 litres per minute. Less in the winter. Only usable for a single outlet, and even then it's the equivalent of filling a bath using an electric shower.

    The existing electric shower would have to be removed, or at the very least reconfigured so that it could not be used at the same time as the boiler.
    All that assumes the existing supply is suitable for an electric combi. Many are not.

    Heating options:
    Gas or oil - cheapest to run, cheapest to install
    ASHP - running costs similar to gas, but far more expensive to install
    GSHP - running costs similar to gas, but even more expensive and disruptive to install and simply not possible in a majority of locations
    Electric - cheap to install but by far the most expensive to run, typically 5x more than gas.

    E7 and storage heaters are a halfway house, moderately expensive to install but cheaper than anytime electric heating but only because of the E7 overnight pricing, and that assumes that E7 will continue for years into the future. It probably won't.
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