Moving from a property with combi boiler to electric immersion

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My partner and I are set to be moving to the countryside, from the city, which we hope will improve our balance of life. As the property, we're moving into has triple glazing and lots of insulation, I didn't consider energy costs being more naively. However, when I've noticed it only has an electric immersion, which the shower uses as well instead of an electric shower.

I did some rough workings, and it will cost between 75% - 100% extra to heat the water, compared with the gas price to heat the flat and water currently. Because of it being a completely different style of life, I didn't mind entertaining a small extra cost. All in, the new property would possibly work out £60 cheaper each month, but that's before the extra travel costs and may mean possibly needing to buy a new car.

Now that I've realized this, I feel a sense of dread, and that it's a backwards step compared to being in a property with a combi boiler.
I've asked if I paid for an electric shower unit, if this can be installed and this could reduce the cost and reliance on the immersion heater.

I've been told it's a top range tank, but it will take 6KW over 2 hours to heat. It's a variable tariff and no economy 7.

If I had it on for 2 hours from 4am - 6am, had a short morning shower, would the water still be hot enough for a shower when I return home just after 7pm? Or would I need to maybe put it on for another hour at 5/6pm?

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  • [Deleted User]
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    Heat loss from modern hot water tanks is normally quoted as between 1 and 3 kWh per day, so your daily use would be that plus topping up whatever you take out with your shower(s).

    I have a system boiler, so not an immersion heater but still a hot water tank, and I only have my hot water turned on once a day.
  • throughtheblue
    throughtheblue Posts: 265 Forumite
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    edited 29 December 2022 at 6:45PM
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    Heat loss from modern hot water tanks is normally quoted as between 1 and 3 kWh per day, so your daily use would be that plus topping up whatever you take out with your shower(s).

    I have a system boiler, so not an immersion heater but still a hot water tank, and I only have my hot water turned on once a day.
    If the property had an electric shower, then I wouldn't be too concerned about the electric immersion. We could boil a kettle for washing up and possibly just put the immersion on occasionally.

    I'm 30 now, and haven't lived with an immersion since I was a kid, and it feels like a massive backward step I hadn't accounted for stupidly.

  • ChaunceyGardiner
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    it will cost between 75% - 100% extra to heat the water
    That seems a bit low. Electricity is 3-4 times more expensive than gas. A combi boiler isn't quite as efficient as an immersion, but there's no tank to lose heat either.
  • throughtheblue
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    it will cost between 75% - 100% extra to heat the water
    That seems a bit low. Electricity is 3-4 times more expensive than gas. A combi boiler isn't quite as efficient as an immersion, but there's no tank to lose heat either.

    I agree with you, but because we currently have a bath, but won't there, my partner won't be having 4 full baths each day.

    It's only rough workings out. For instance, if our current gas for heating and water is £80. Then the new place is we use 12kwh per day at 35p (rough guess for October), then it would roughly work out £136 to heat the water. For heating we could use a log burner, and the place is triple glazed and packed with insulation, so I haven't thought to hard about heating yet.

    When my partners been away for weeks some winters, I don't even put the heating on.
  • BUFF
    BUFF Posts: 2,185 Forumite
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    do you know the capacity of the hw tank?
  • dunstonh
    dunstonh Posts: 116,661 Forumite
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    Now that I've realized this, I feel a sense of dread, and that it's a backwards step compared to being in a property with a combi boiler.
    Funny as I would consider a combi a backward step compared to a well lagged tank.   I suppose it is all about familiarity.  Once you get used to it, you won't care.

    First thing, are you sure its only an immersion heater that heats the water?  Many homes have boiler heated and an immersion heater as backup?

    I've been told it's a top range tank, but it will take 6KW over 2 hours to heat. It's a variable tariff and no economy 7.
    We have an immersion heater but only as a backup to the oil boiler (once when the boiler failed and each time the boiler is serviced and is turned off the day before)    The tank is very well lagged.   With our water use we find the tank only needs about 15 minutes to reheat it to the required level.  So, the water gets heated for up to 30 minutes in the morning and 30 minutes in the evening.  Maybe the 2 hours mentioned is from cold.  

    How well lagged is the tank?  A well lagged tank should keep it hot for two.days.  Hence only the need to give it short top ups reheats unless you have particularly deep baths.
    when I've noticed it only has an electric immersion, which the shower uses as well instead of an electric shower.
    That is good news as electric showers (as opposed to power showers) use more electricity.
    I am an Independent Financial Adviser (IFA). The comments I make are just my opinion and are for discussion purposes only. They are not financial advice and you should not treat them as such. If you feel an area discussed may be relevant to you, then please seek advice from an Independent Financial Adviser local to you.
  • throughtheblue
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    BUFF said:
    do you know the capacity of the hw tank?
    My memory is it didn't seem huge, maybe 120-140l.

  • throughtheblue
    throughtheblue Posts: 265 Forumite
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    edited 9 September 2022 at 10:07PM
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    dunstonh said:
    Now that I've realized this, I feel a sense of dread, and that it's a backwards step compared to being in a property with a combi boiler.
    Funny as I would consider a combi a backward step compared to a well lagged tank.   I suppose it is all about familiarity.  Once you get used to it, you won't care.

    First thing, are you sure its only an immersion heater that heats the water?  Many homes have boiler heated and an immersion heater as backup?

    I've been told it's a top range tank, but it will take 6KW over 2 hours to heat. It's a variable tariff and no economy 7.
    We have an immersion heater but only as a backup to the oil boiler (once when the boiler failed and each time the boiler is serviced and is turned off the day before)    The tank is very well lagged.   With our water use we find the tank only needs about 15 minutes to reheat it to the required level.  So, the water gets heated for up to 30 minutes in the morning and 30 minutes in the evening.  Maybe the 2 hours mentioned is from cold.  

    How well lagged is the tank?  A well lagged tank should keep it hot for two.days.  Hence only the need to give it short top ups reheats unless you have particularly deep baths.
    when I've noticed it only has an electric immersion, which the shower uses as well instead of an electric shower.
    That is good news as electric showers (as opposed to power showers) use more electricity.

    It's only the immersion, as it's a rural property and no gas supply.

    I can't remember the lagging, but the owner is conscious of design and efficiency, so I'd say well lagged/insulated, but I have asked.

    I know electric showers are more expensive, but if we're using an 8.5kwh shower for a couple of minutes per day each, would that not mean we'd be using the immersion less.

    If like yours, once heated, it would only need 30 minutes in the morning and 30 minutes in the evening, then that would reduce my concerns massively. If that was the case, once up to temp, it would need 3kwh to maintain temp each day, instead of my estimation of 10/12kwh.

    Edit: Also, Im looking at the 'willis external immersion' (3kwh), which can be added to the immersion, and heat 4.5l of water in 5 minutes. This might make things more efficient.
  • dunstonh
    dunstonh Posts: 116,661 Forumite
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    It's only the immersion, as it's a rural property and no gas supply.
    Same here except most rural properties in our area are on oil or LPG.

    If like yours, once heated, it would only need 30 minutes in the morning and 30 minutes in the evening, then that would reduce my concerns massively. If that was the case, once up to temp, it would need 3kwh to maintain temp each day, instead of my estimation of 10/12kwh.
    Like you, but 3 lots of showers a day and power shower (pump).   The oil tank was filled up in April and hasn't even gone down a bar on the meter.  It's all it has done since then is the a few weeks of heat in April and then heating off with the water the only thing on with those two 30 minute boosts.  (and the evening one doesn't even tend to stay on longer than 10-15 minutes most days.  

    I use 3000 litres of oil a year.    (3 fills of 1000 litres). It hasn't used even 100 litres since April.  i.e. 5 months of the year when only the water has been heated, it has used just over 3% of my annual oil use.  The real cost is in heating, rather than water.

    I may be on oil and the tank heated from the boiler, but it indicates how a well-lagged tank doesn't use much energy to heat.  I don't think you will have much to worry about provided it is well lagged.     And those times I have used the immersion heater, It only needed about 10 minutes on to bring it up to temp.  


    I am an Independent Financial Adviser (IFA). The comments I make are just my opinion and are for discussion purposes only. They are not financial advice and you should not treat them as such. If you feel an area discussed may be relevant to you, then please seek advice from an Independent Financial Adviser local to you.
  • lohr500
    lohr500 Posts: 968 Forumite
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    Related to dunstonh's question, how is the house heated? Is that all electric as well?
    You mention that it has no mains gas, but does it have oil or LPG?
    If it is electric heating, what type? Night storage heaters on an Economy 7 type tariff or conventional electric heaters running on a single rate tariff?

    Not to add to your worries, but if the house is heated by electricity and you intend to keep it warm this winter then the water heating cost could well be a small percentage of your total consumption.

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