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danielleomosefe
Rank 2
September 4, 2026
Solved

Why is my storage water heater not working at off peak times?

  • September 4, 2026
  • 17 replies
  • 106 views

Hi! I just moved to my flat about a month ago and I'm still trying to figure out everything. I noticed a something strange yesterday, when I tried turning on off peak and normal supply between 12:30 and 7:30 which is my off peak period, the off peak active light did not come on but later on in the day by between 7 am and 12pm it came on and I had to turn it off as it was charging me heavily. Does anyone know how to resolve this issue please?

 

Best answer by Firedog

Do you know if storage water heater off peak light coming on during the peak hours is normal?

No, that’s not normal. It should only be on during offpeak hours (and, I think, when the immersion heater element is actually taking power, but that might not be the case). 

I see you have an EDMI communications hub (on top of the meter). This means you’re in North Britain (i.e. north of about Manchester). And, if I remember correctly, that odd Region Specific plan was intended to replace the radio-controlled plans in Load Managed Areas, mostly in Scotland. At one stage, the timings for Shetland activated the heating/hot water during these periods: 1.30am - 3.30am, 8.00am - 11.00am, 4.30pm - 5.30pm & 10.00pm - midnight; so a total of 8 hrs of off-peak over the day.

These plans were introduced so that the electricity distributor (DNO) could vary the load  across the area so as to avoid overloading flaky powerlines - meaning your timings might be different from a neighbour’s.

If this is the case, then the immersion heater coming on at odd times of the day may well be in order (even if it’s not what I’d call ‘normal’!). You might have to ask your DNO what times you could expect OVO to be delivering offpeak electricity if Support can’t find out for you. That’s your first task.

17 replies

Rank 12
Bendog
Rank 12
September 5, 2026

Looking at your image, you have both the Normal Supply and Off peak supply switches in the “On” position. What kind of meter do you have for your electricity? If you are not sure, it would be helpful if you supplied a picture of the meter so that its associated wiring can be seen. There are a number of people here who are experts with heating and hot water in all electric properties.In the meantime, I would turn both switches off. I believe that the Normal Supply switch is only for use if you need to top up your hot water during the day for some reason when you then use the Boost buttons. I have found a link to this controller and there is also a link on the same page for a user manual. I am not sure that this will fix your problem. https://www.securemeters.com/uk/product/electric-water-heating-controls/bx2000-hot-water-boost-control/

    Rank 2
    danielleomosefeAuthor
    Rank 2
    September 5, 2026

    I have a pre payment meter and I have also has to turn both switches off as it was charging me 62p per hour just now. I would have to look for a user manual. Thanks for the link!

    Rank 12
    Bendog
    Rank 12
    September 5, 2026

    I assume that you have registered for an account with OVO? However, it would still be useful if you could take a photo of your meter (edit it to obscure the meter number) showing all connections in the area where it is installed. Do you also have storage heaters for heating?

    Rank 2
    danielleomosefeAuthor
    Rank 2
    September 6, 2026

    Alright. Will do!

    Rank 2
    danielleomosefeAuthor
    Rank 2
    September 6, 2026

     

    Rank 2
    danielleomosefeAuthor
    Rank 2
    September 6, 2026

    These are pics of the fault and my meter!

    Nukecad
    Super User
    NukecadSuper User
    Super User
    September 6, 2026

    From a quick look there your IHD is saying that at 6:20 you are using 3.28 kW, and that is costing you £0.65 per hour.

    If you work it out (65 / 3.28) that’s a tariff of 19.8147 pence/kWh which seems to be an  off-peak rate, although high for current OVO E7 rates.*
    TBH though I’m not sure what the current E7 rate for PAYG customers actually is (and I cant look it up at the moment because the ‘Our Plans’ page is giving an error).**

     

    *It may simply be that your IHD does not have your correct current tariff set, it happens.
    “£” values shown on a IHD are only an indication and can be inaccurate if the tariff rates on the IHD have not been updated to your current tariff.
    You will be charged at the correct rate of your Plan, whatever the IHD is saying.

    **If you look at your plan on the account portal, or app, or on the email/letter that you got when joining OVO, or on a statement if you have had one, then what does it say that your peak and off-peak rates are?

    I said, Hey - Watts going on.
    Rank 2
    danielleomosefeAuthor
    Rank 2
    September 6, 2026

    Hey, thanks for explaining that was very helpful. My rate is actually a little lower from the app and the water heater comes on at about 6 or 7 am and runs at off peak during the day (even until afternoon) charging at the same rate so I think I may call ovo tomorrow all the same. Thanks a lot! 

     

    Nukecad
    Super User
    NukecadSuper User
    Super User
    September 6, 2026

    the heater comes on at about 6 or 7 am and runs at off peak during the day

     

    Err, no. E7 is not off-peak during the day.

    It is off-peak overnight to heat up the storage heaters that then release the stored heat during the day.
    The actual off-peak hours vary slightly depending on what region of the UK you are in.

    Have a read of these two guides:

     

    https://www.ovoenergy.com/guides/energy-guides/storage-heaters-guide-everything-you-need-to-know

     

     

    Is there a separate timer for your heating, or do the heaters each have their own timer?

    If so then are the timers set correctly to match your off-peak times?

    We have seen before where the timers for the storage heaters had not been set to match off-peak times so were using peak rate electricity.

    I said, Hey - Watts going on.
    Firedog
    Super User
    FiredogSuper User
    Super User
    September 6, 2026

    Hello ​@danielleomosefe 

    Just to clear up a couple of points.

    1. ​@Nukecad worked out your offpeak rate (at 06:20) to be 19.81p/kWh, while your plan says it should be 18.88p. The difference is just the 5% VAT which isn’t included on the Plan page. 
    2. Your meter (thanks for the clear photo!) shows two things:
      1. the current reading of the offpeak register called Rate 2. The display will usually cycle through a number of screens, including TOU Rate 1 (peak) and Rates 3 and 4 (unused unless you start generating your own power using solar panels or a windmill!). 
        This doesn’t mean that the offpeak register is active, even though it is …
      2. In the bottom corner, LC indicates that the switch (called ALCS) inside the meter is active, delivering power to the grey cable marked 5 L. If the ALCS is properly configured, LC should go away at the end of the offpeak period. If you see LC during the daytime, it might indicate that the ALCS needs tweaking.
      3. The 3.28 kW reading on the IHD is quite normal when the immersion heater is on - they are usually rated at about 3kW.  The Cost per hour of £0.65 is an instantaneous figure - it just shows what the cost would be if you continued using 3.28 kW for a whole hour. Common hot-water tanks usually only take a couple of hours to heat up from cold, so a full tank of hot water shouldn’t use more than £2 of electricity a night.
      4. I’m not familiar with the immersion heater timer you have. I’ll have a look at the leaflet Nukecad helpfully unearthed, but the two switches are for two separate heating elements in the tank, the offpeak one is at the bottom and the normal one near the top. The offpeak one is only active in offpeak hours (that’s what the ALCS is supposed to do) and explains why the red light is on at 06:20. It should go off when the offpeak period ends. 
        I would expect that the Normal switch will only deliver power to the upper element when you press one of the Boost buttons. This is for emergencies - when someone’s used all the hot water and you need to wash up, say. But I might be wrong … Please come back and tell us whether the offpeak light is on anytime during daytime.
    Noel | I have no official status; I'm just a volunteer who comes here to help other customers. My gear: Aclara SGM 1416-B Electricity-only E7 meter; Chameleon IHD3-PPMID-AAA | It may look as if I know what I’m talking about, but don’t let that fool you. |
    Rank 2
    danielleomosefeAuthor
    Rank 2
    September 6, 2026

    Thank you so so much! I now undertand. I would say the reason I was so alarmed initiatly was the off peak light was on at 12pm but I really appreciate the clarification, I now understand the charges. Do you know if storage water heater off peak light coming on during the peak hours is normal?

    Firedog
    Super User
    FiredogSuper UserBest Answer
    Super User
    September 6, 2026

    Do you know if storage water heater off peak light coming on during the peak hours is normal?

    No, that’s not normal. It should only be on during offpeak hours (and, I think, when the immersion heater element is actually taking power, but that might not be the case). 

    I see you have an EDMI communications hub (on top of the meter). This means you’re in North Britain (i.e. north of about Manchester). And, if I remember correctly, that odd Region Specific plan was intended to replace the radio-controlled plans in Load Managed Areas, mostly in Scotland. At one stage, the timings for Shetland activated the heating/hot water during these periods: 1.30am - 3.30am, 8.00am - 11.00am, 4.30pm - 5.30pm & 10.00pm - midnight; so a total of 8 hrs of off-peak over the day.

    These plans were introduced so that the electricity distributor (DNO) could vary the load  across the area so as to avoid overloading flaky powerlines - meaning your timings might be different from a neighbour’s.

    If this is the case, then the immersion heater coming on at odd times of the day may well be in order (even if it’s not what I’d call ‘normal’!). You might have to ask your DNO what times you could expect OVO to be delivering offpeak electricity if Support can’t find out for you. That’s your first task.

    Noel | I have no official status; I'm just a volunteer who comes here to help other customers. My gear: Aclara SGM 1416-B Electricity-only E7 meter; Chameleon IHD3-PPMID-AAA | It may look as if I know what I’m talking about, but don’t let that fool you. |
      Rank 2
      danielleomosefeAuthor
      Rank 2
      September 6, 2026

      Thanks a lot, you explanation makes a lot of sense and it's so detailed. I will get in contact with OVO to check. Thanks once more!!

      Chris_OVO
      Community Manager
      Chris_OVO
      Community Manager
      September 7, 2026

      It's great to see everyone getting involved and lending a hand! Thank you all for your contributions! We’d love to hear about your progress, so keep us posted ​@danielleomosefe 😊

      Renewable energy jokes never get old.
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