Off peak storage heater charging duration

We’ll have to make some assumptions about your system, until you give us more details.

The normal arrangement is for the storage heaters to start charging at the beginning of the offpeak period, in your case at midnight. Unless you have further control over them, they will keep charging until they’re fully charged. Some more modern ones will limit the amount of charge they take according to what they expect to discharge the following day. Two hours may be enough. 

Do you have a hot water tank also being heated during offpeak periods? An immersion heater will typically draw just as much power as a storage heater. 

We’ll be able to offer better advice once you tell us exactly what equipment you have.

Firedog thank you for your reply.

I've got 1970s Dimplex storage heaters & no off peak immersion heater was on. My new tariff is OVO Economy 7 after the smart meter was fitted - hours defined as midnight - 7am.

After my new smart meter was fitted my off peak meter red light started blinking rapidly last night at 12.03am & stopped at approx. 3.50am. Thats 4 hours off peak instead of the 2 hours off peak before my smart meter was fitted - when I was on an Economy 7 off peak type tariff with a Radio Teleswitch.

That's double the off peak hours (just for the storage heaters) & cost.

I agreed to the smart meter because I was told the signal was being turned off at the end of June. I was given an installation appointment 48 hours later. 

The IHD hand held device works well.

I've read on the OVO Forum about asking the OVO support team to reconfigure the ECAUL/ALCS configurations via SMETS commands - is this relevant in my case ?

Thanks.

In the first instance, yes. We find that the ECAUL/ALCS reconfigure trick solves most of these cases so it’s worth a try. The worst it’ll do is just refresh with the exact same config as the meter already had, or fail to go through and do nothing.

Blastoise186 thank you.

Thank you.

OK, so the immersion heater is switched off. I wonder how you heat the water now? Or do you perhaps, like me, do away with using the hot water tank and boil up a kettle or two when you need some hot water? What about baths or showers?

AS the name implies. Economy 7 gives seven hours of power at a lower rate, specifically to allow for charging storage heaters and water heaters overnight. Any electricity you use between midnight and 07:00 will be billed at the lower rate, not just that used by the heaters. 

What controls do you have for the storage heaters? For example, some have dials on the top for ‘input’ and ‘output’, but there are many variations. It may be possible to achieve what you want by adjusting the available controls. 
  

Yes, it sounds as if that’s what it takes to charge up the heaters. If they don’t discharge fully during the day, they will take less charge the following night, but I don’t think that’s particularly likely - older heaters aren’t as good as modern ones at retaining the heat.
  

No. Your meter appears to be working just as intended: it starts recording offpeak usage at 00:03 and will do so until 07:03. The heating circuit which powers your storage and water heaters will be live for exactly the same period. 

Once we know what controls you have for your storage heaters, and how you heat water, we’ll be able to make more suggestions. It would help to know the make and model numbers of the heaters, and photos are always welcome.

Firedog - my immersion heater was not turned on during this off peak period. It is used earlier. My daily electricity use is the same.

The OVO electrician replaced my previous meters with a smart meter. That's the only change. Now my off peak meter (storage heaters charging only) is on from midnight - 4am approx instead of two 1 hour pre smart meter charging periods - increasing the bill.

The storage heaters heat input dial settings (for colder weather) have been left the same as pre smart meter so the installation of the smart meter - & its settings - is the only change made.

Its nothing I've done at this end so it must be the new smart meter & its internal settings controlled remotely by OVO.

Thank you, but I’m still a bit confused about the arrangement you have. 

• Where do you live? The first part of your postcode should be close enough for us to nail down the tariffs and timings of the various plans, both before and after your meter exchange.
• How do you pay for your electricity - Direct Debit, on receipt of bill or prepayment? This also influences which plans are or were available to you. 
• What was the name of the tariff you were on before the meter exchange? It should be given on a recent bill, e.g. THTC, Simpler Energy, Superdeal … there are many possibilities.

I would advise against asking for the ECAUL request to be sent, because there’s nothing to suggest that the load switch in your meter isn’t doing just what it’s supposed to: to make electricity available to power-hungry equipment like heaters during the night at a lower rate. 

You say “my immersion heater was not turned on during this off peak period. It is used earlier.” There is only one offpeak period each day - from midnight to 07:00 (+ 3 minutes). If you had the immersion heater switched on before midnight - perhaps using a boost function - it would have been using electricity at the peak rate, which may be much more expensive. 

You haven’t exactly told us what has changed, just that the change was caused by the new meter. You mention that the bill has increased - where do you see this? Are you comparing daily meter readings from before and after the meter exchange?

If your previous arrangement gave you enough heating from the storage heaters to be comfortable all day without supplementary heating*, then you should be able to limit the amount of charge the heaters take by screwing down the input dial. It sounds as if it’s the output setting that’s dictating how much charge they take, and this is demanding almost 4 hours of charge. Because the power to the heaters is no longer restricted to only two hours a day, they are taking whatever they think they need. The restriction made sure they couldn’t achieve this before, so it’s plain that you’ll have to vary their controls to match your requirements. 

Your old system depended on a radio signal to energize your heating equipment. That radio signal will not be broadcast after 30 June this year at the latest, so it’s time to adapt to the new arrangement. It’s unlikely that you will be much out of pocket as a result of the meter exchange. 

*  I’d be surprised to hear that this is in fact the case. My own experience of old night storage heaters is that while they might keep the temperature at a reasonable level until sometime in the afternoon, it’s all downhill after that. I have either to light the fire at sunset, or cocoon myself in an electric blanket to ward off hypothermia,  should I feel like watching television of an evening.

Firedog - thanks for your reply.

Postcode - TW5.

Payment on receipt of bill. 

Tariff before smart meter - Simpler Energy - Flex Rate 01 October 2024, & Simpler Energy - Flex Rate 01 January 2025 (copied from bill).

The smart meter was installed & OVO gave me a new tariff - Economy 7, hours defined as midnight - 7am.

Before my smart meter was installed my Off Peak meter red light blinked quickly from 10.30pm -11.30pm & also 4.30am - 5.30 am (total 2 hours) caused by my storage heaters being charged. No other Off Peak using equipment was on during that period.

I thought that my new smart meter would just send my meter readings automatically to OVO, that my new Economy 7 tariff times would be moved to 12am-7am, & that my storage heaters would continue to be charged for two 1 hour periods i.e. = same cost.

I don't understand why my smart meter is running off peak for 4 hours instead of 2 - doubling my nightly Off Peak cost.

One odd thing occurred last night.

Because my storage heaters were being charged for 4 hours instead of 2 hours they seemed hotter than before the smart meter. I turned down each storage heaters' heat input dial for safety's sake at 4am . The smart meter red light blinking began slowing down markedly & nearly ceased. My IHD unit then showed minimal electricity use.

I obviously can't wake up at 4am to manually reduce each storage heaters' heat input dial.

Before the smart meter was installed the storage heaters were charged up off peak for two 1 hour periods each night. Why 4 hours now ?

I want my storage heaters to be charged up for two hours each night to have the same cost.

I can’t be sure about any of this, but from what you say, before your smart meter was installed, you had electricity at offpeak rates to your storage heaters for two hours each day. You haven’t said when your water tank is heated, even though it could well be using as much energy as a storage heater. It could be that your immersion heater was also being powered at the offpeak rate. This could be a major element in your electricity bill.

On the old plan, you were paying 22.29 p/kWh for the offpeak rate for heating and 27.47 p/kWh for peak rate (anything other than heating). 

On your new Economy 7 plan, the offpeak rate is 19.56 p/kWh while the peak rate is 29.18 p/kWh. 

It is quite normal for customers with storage heaters to use the largest share of their energy on heating. If this is your situation, then the 12% saving in offpeak usage costs will outweigh the 6% higher peak usage cost. Only you know your usage pattern, so you will have to do your own sums to work out what the costs might now be.

Now, the two-hour/four-hour charging question. Your storage heaters have a certain capacity, which is usually designed to deliver an acceptable amount of heat during the day. What is acceptable depends on the size of the space being heated and the preferred temperature. How to achieve that temperature depends on the weather.

To give that desired amount of heat would normally involve charging the heaters for half the number of hours you want to maintain the temperature during the day. Seven hours of charge would give 14 hours of heating. You have clearly been making do with less, to keep costs down. I see that you still haven’t made any mention of supplementary heating, so it could be that the four hours or so of heating you were probably getting during the day was enough to keep you comfortable. Is that the case?

The input setting on the heaters dictates how much power the heater draws. The ‘cold weather’ setting is probably the highest, meaning that the heater will draw as much power as it can until it has reached its capacity. If the heater itself feels too hot after charging, you should try turning the input dial down to, say, its middle setting. You can see on the IHD the effect of doing this, because the kW being drawn should be less at a lower input setting. You’ll have to experiment to find the setting that works for you. There should be a thermostat in the heater that will prevent it from overheating.

If you have access to your online account, you should be able to see just how much the heaters are consuming every half-hour during the night. The IHD can also tell you how much electricity was used since midnight, say. 

I’m writing this to explain that it’s not just how many hours the heaters are charging for that counts, but also how quickly they’re charging. This also matters because the heaters are clearly not particularly well insulated (they wouldn’t ever feel ‘too hot’ if they were), so they are discharging some heat while they’re charging - during the night when you probably don’t need it. The longer you can make the charging part last, the longer the heater will be able to deliver heat the following day. 

Thank you for reply Firedog.

My immersion heater has no timer. It is manually turned on & I don't put it on after midnight so its electricity consumption wasn't on during my storage heaters 4 hours  charging.

I don't have any supplemental heating. My storage heaters are wide stand alone ones which are quite good. I have one wall mounted in the hall (bad electricity board shop advice) which is ineffective.

Explaining the p/kWh of my old/new tariffs was very useful. The lower Off Peak rate will help.

I've never had any timer control for my storage heaters. It was always two 1 hour off peak charging periods from their installation. I assume that the electricity board electrician set it up that way when he installed them or maybe the electricity company did that at their end ?

I understand your point that it is not only how long my storage heaters are being charged, it is also how quickly. The OVO smart meter electrician upgraded some of my meter cables to wider ones 😧 - perhaps that means that more current goes to my storage heaters ?

However I'm missing something.

I don't understand why a new smart meter with a new tariff with different Off Peak hours & pricing would cause my storage heaters to receive charging for 4 hours instead of the previous pre smart meter 2 hours.

Even with my new tariff 12% off peak reduction 4 hours charging will be more expensive than 2 hours. My IHD showed an off peak £2.25 approx hourly charge. 2 extra hours  = £4.50 x 30 days = £135 extra a month. OVO gains - but I have extra cost which wasn't mentioned by OVO on the phone when they discussed a new tariff for me.