Electric hot water

I live in a 1 bed flat and the whole building is electric only. I switch hot water on as and when I need it. Would it be cheaper to have it on a timer? The smart meter seems to go through the roof when I put it on and I leave it on at least an hour before having a shower. Any advice appreciated 


  • Farway
    Farway Posts: 13,025
    Homepage Hero First Post Name Dropper Photogenic
    As and when is fine if it's just you. 
    If you have off-peak elect available then a timer to take advantage would save money during the cheaper period

    You could experiment on time you require to leave it on for a shower, shorter or cooler showers for instance
    Eight out of ten owners who expressed a preference said their cats preferred other peoples gardens
  • mmmmikey
    mmmmikey Posts: 1,594
    First Post Name Dropper First Anniversary Combo Breaker
    Hi and welcome to the forum. Do you know whether you're on a standard single rate tariff or Economy 7 (or possibly something else)? It makes a big difference to the answer to your question. If you're new to the world of energy and my question means nothing to you then you're certainly not alone. If you have a look at your latest bill it should tell you the name of the tariff.
  • Veteransaver
    Veteransaver Posts: 343
    Name Dropper First Post
    Are you on economy 7 or other cheap overnight tariff? Do you have storage heaters (assume you may if the flats are all electric)
    If not then it will likely cost you more if you heat it over night rather than as and when you need it as you'll lose more heat from the tank.

  • Scot_39
    Scot_39 Posts: 1,689
    First Post First Anniversary Name Dropper
    edited 8 February at 2:34PM
    So just to be clear - I will assume you have a tank fed shower from mains pressurised hot water cylinder (from mixer tap or mixer thermostatic shower controller) not uncommon in modern builds and flats even more so - and not a conventional old style cold water fed electric shower.

    Does the tank immersion heater actually stay on the typically 3kW power draw for the full hour on the IHD if you leave it on ?

    It is of course regulated by a thermostat as well - so may be cutting out before you switch it off if a light user (less likely with a tank fed shower though).  

    1 hour would maybe cost you c85-90p per day at flat rate - less on E7 if you have it as an option.  Not much for the convenience of hot water on demand if you can afford it.

    Some others here in past have posted saying they only charge HW tank for 1hr every 2-3 days - and that gives them enough hot water for say 2 showers per day over those 2-3 days - but that depends on size of tank and how long, how hot and how high a flow rate your showering at.

    But a lot depends on the shower - duration and flow rates - as some can use almost twice as much flow as others - power showers can be rated on a quick google at say 15l+ per minute.  A 10m shower at 15l/min - even at 35C (tank 60C, cold incoming 10C - so 50% hot in mix) could use 75l - then add in other light day use (toilet basin, kitchen sink for dishes etc).

    Heating 75l to 60C from 10C incoming - would cost about c4.4kWh - just the water - so would need about 1.5 hrs on a 3kW immersion heater.

    Other usage and pipe runs add up to - a kitchen sink plastic wash basin - maybe 8-10l if fill - a toilet basin maybe 5l if fill etc - plus maybe a couple of litres per tap use in pipe run off volume.

    Your actual need ?

    A way of measuring Hw energy use (and secondary losses) might be to actually let the heater cut out on it's thermostat - and see how much time / energy it takes at it's rated power (typically 3kW) it takes on say 3 consecutive typical HW use days - and take average of last 2 - and use that to set your timing guidline for future use.
    And you may even be able to drop it a little - and live with slightly lower temperatures - but I'd still let the tank cut out on thermostat at least once per week.

    Single Rate vs E7

    Some "all electric" homes are wired for multirate electric - for HW and heating - some modern flats sadly are not.  Worst case some are only partially wired for E7, billed on E7 - but have panel heating that consumes most of their power mix charged at peak day rates.

    Do you know what sort of meter / tariff you are on 
    - does it have E7 or economy 7 in title ?
    - one rate or two on bills ?
    - one reading or two on meters ?

    Your tank if home was designed for E7 - may even have 2 heaters - one near bottom wired to meter switched off-peak E7, the other half way up or so - available as a manual boost top of tank from 24.7 (peak rate most of the time on modern E7 - all of the time on some older dual meter systems).

    Fitting a hard wired spur timer to an immersion heater is not a big job - but it is one for an electrician these days.

    MY own HW heating costs

    I have an electric het cold fed shower - for a longish 10m shower - that would use c1.5kWh - I suspect my typical showering less than that - just sub 1kWh.  Not quite got it down to 4m advice every day though - that would be 0.6kWh.  And thats to be frank - a pretty feeble flow rate compared to mixer type showers I've tried elsewhere in hotels and apartments abroad.

    I still let my HW tank top itself up on off-peak rates daily - to the thermostat setting - I tried the whole switch it off then on again for a few days at a time - if it saved much it was lost in my daily noise (it should in theory have cut down a bit on the c1kWh+ daily losses at 60C modern well insulated tanks can achieve) - but for me was annoying when I forgot to switch it back on in time and had no or not hot enough water when I wanted it.  Probably costs me c50-55p off peak per day (at single rate more like 80-85p) over and above the shower - another c20p off peak - c40p peak depending on time of day.
    But even at around £1 a day - and thats enough that it certainly adds up over the year - if struggling financially it's non trivial - but for me it's just a convenience / personal choice thing - I'd rather cut elsewhere if had to - than not having hot water on demand when I want / need it.

    It's one of the things that makes cold days more bearable - a hot shower, hot water to rinse hands / wash face etc, hot meals rather than cold, hot drinks rather than cold etc - it just helps not only physically - but I suspect psychologically as well.

    Showering Frequency

    My father was tought how to wash the essentials daily on just one pint of water in the army when on active service. He still used a basin and 2 wash cloths rather than showering some days until he died.

    And remember - showering once or more a day is a modern norm - people of my parents generation - working classes - wouldn't have had showers for most of their lives and wouldn't have dreamt of having a bath every day. 

    The old saying - now used as insult / joke - "has a bath once a month - whether <he/she/they> need it or not" - has basis in fact.

    If not particularly physical / active showering daily possibly even overkill.

    Sites like WebMD - say 2-3 showers per week should be enough - if not actually better for health than showering daily.

    So skipping on odd days - of course another way of saving money.

Meet your Ambassadors


  • All Categories
  • 341.8K Banking & Borrowing
  • 249.7K Reduce Debt & Boost Income
  • 449.2K Spending & Discounts
  • 234K Work, Benefits & Business
  • 606.2K Mortgages, Homes & Bills
  • 172.5K Life & Family
  • 246.8K Travel & Transport
  • 1.5M Hobbies & Leisure
  • 15.8K Discuss & Feedback
  • 15.1K Coronavirus Support Boards