Updated on 29/05/25 by Ben_OVO
This sounds like a fairly simple fault cropping up when rewiring a THTC system to a smart metered one. I would expect your immersion heater to be energized only during offpeak hours, governed by a switch inside the new meter. We’ve seen several cases where this hasn’t been the case after similar meter exchanges, but it is often quite easy to correct. We’d have to know a lot more about your system first, though, to be able to suggest what you might have to say to OVO Support to get them to sort this out.
- Please post some photos of your system:
* a close-up of the meter itself clear enough for its display and other markings to be legible. Touch one of the buttons to light up the display before taking the picture, and note the time you take it¹.
* A view of the box or cupboard or backboard where the meter is mounted, showing all the cables to and from the meter.
* A close-up of the consumer unit (‘fuse box’) with its lid propped open, clear enough for the labels on the individual breakers to be legible if possible. If there’s more than one CU, all of them. - What sort of space heating do you have?
* Night storage heaters
* Direct heaters (panel, electric radiators, IR ...)
* Solid fuel heater (e.g. a wood-burning stove)
* Other … - How do you know that the immersion heater is warming up during peak hours - can you hear it and/or is the red lamp lit?
- Is the switch in your picture the only one you have for the water heater?
[1] If you can take close-ups of the meter both during the advertised offpeak hours and outwith them, so much the better. 3 pm and 5 pm should make sure you’re in the zone.
Firefox. Thank you for replying. My new meter has only been installed for two days but suddenly seems to be working. I left the immersion button in the on position and monitored and it is suddenly working. The immersion light goes on and off at the appropriate times that correspond with Economy 9 hours. Closely monitoring my smart meter too. What a difference! For some reason I had been put on the Simply Energy plan, and there was nothing simple about it. It was working out very expensive, so I was pleased to see that the amount used and was a vast improvement. Just a pity it has taken so long to get these new tariffs, but they are here now. I will keep my Diect Debit the same and pay off my outstanding money owed. The economy 9 plan has various times during the day and night, seems to keep the hot water constant, and the cost much better. Back to the way it was in the old THTC days. Thanks again. Very useful this forum!
Thank you - it’s good to hear that things are now working for you as expected.
Just a brief word about hot water: unless you have a large tank or use a lot of hot water, there is probably no need to have the immersion heater energized for nine hours a day. Although the thermostat will shut it off when the target temperature is reached, you might just be keeping the loft nice and warm during the night for the small creatures that live up there. I would experiment for a few days to find the most economical way of heating the water. For example, if the tank is quite hot all the way to the bottom one morning, switch the immersion heater off and see how long the hot water lasts. You may find that it’s still hot enough a day or two later. If it’s still warm two mornings later, you could get away with turning the immersion heater on at bedtime every other night and off again the following morning. If it’s not hot enough, make the on/off performance a nightly routine.
We often see that immersion heaters left to their own devices can be real electricity hogs.
