Just a reminder - Octopus has previously warned they don’t support THTC at all. Proceed with extreme caution. I also cannot guarantee they’ll be able to upgrade/replace such meters - OVO is the only supplier known to definitely 100% be working on this.

The move to Smart Meter based THTC will indeed make it so one meter does everything, but the Tariff won’t change - you’ll still keep it. The migration basically just gets rid of the meter spaghetti and makes things far simpler.

Hi Colin

I would completely agree that it's vital that those who currently have access to periods of cheap rate electricity (overnight or otherwise) should be able to keep it. However, you don’t need two meters to achieve that anymore. Its is already possible to get cheap nighttime electricity from Octopus at 7.5p/kWh for the purposes of EV charging (and anything else you fancy doing while the car is charging) and British Gas have a tariff specifically designed for Dimplex storage heaters - can’t remember the rate. Neither of these require two meters or an RTS. In both cases the supplier communicates directly with the device (car or storage heater) via the internet. It seems inevitable that there will be more solutions like this on the way from manufacturers of the goods using the electricity. This is why, in my opinion, OVO are making a bit of a meal of the switch by trying to recreate a centralised solution that just isn’t required. 

In any case, what I actually object to is having to wait for OVO to develop a smart THTC replacement when the more simple solution that would suit me is available now. 

Unfortunately however, not everyone can get off of THTC due to factors beyond OVO’s control. That’s why the industry has no choice but to develop a migration path to Smart Meters for THTC.

From what I understand, OVO would kinda prefer to not have to deal with THTC and be able to just get rid of it entirely, but alas, they sadly can’t until other issues up in Scotland are resolved first - not least transmission and distribution network issues.

It would be interesting to know what the transmission and distribution network issues that impact on THTC are. Could you please explain?

It’s a bit tricky as not a lot of that info is public - some stuff is restricted for reasons of National Security IIRC, on the basis of being Critical National Infrastructure stuff and I have zero access to  information related to that sort of thing.

But it ultimately boils down to limited capacity in certain areas of Scotland. Try to shove too much juice down the lines and, well, this can happen.

So, are you saying that OVO wish to retain control over when storage heaters can and cannot charge as a means of managing the load on the system?

Nope, not OVO. The DNO’s - such as SSEN and Scottish Power Energy Networks - and National Grid ESO ultimately dictate this stuff and OVO has practically no control over it.

Wow!

You should also do your own research - it’s highly recommended that you do. Relying solely on one source for everything can result in things… Not working out...

Blastoise - have you heard from any of your OVO contacts as to when ‘the solution’ will be made available?  I got this from an Advisor earlier this year: “... we're working hard towards it and we might be able to offer this service from June this year s2024].”

The latest data I have is that it’ll all be done by June 2025 at the very latest.

I’m scheduled to visit one of OVO’s offices again in the next couple of weeks. If the right people stop by, I MIGHT be able to find out more but I cannot promise that - this visit isn’t like my last one in November 2022 as it has a very narrow scoped purpose.

Hey @andykelp,

We’re still looking into resolving this as quickly as possible. There has been some industry challenges that have pushed the dates back as @Blastoise186 rightfully said till June 2025. Once more information is available we’ll be contacting affected customers to let them know next steps! 

As Blastoise186 says its not OVO but SSEN, and other affected network operators thats the issue. 

Historically, HydroElectric and SSE, the previous retail suppliers in the North of Scotland, were also the network distributers until the retail and distribution sectors were split.  North of Scotland has very little access to alternative sources of heating, oil and gas for example, and many homes relied on electric heating. However, the distribution network could not meet the demand due to lack of capacity in the distribution system.  Rather than invest in upgrading the distribution system, the industry set up Load Managed Areas where electricity supply could be restricted to allow the distribution system to cope. 

 This is where tariffs like THTC came in (and others like it from SSEB and Scottish Power).  These tariffs enabled the electricity company to switch on and off the supply to premises in an area when demand exceeded capacity in the system but could not obviously suddenly shut off someones electricity. To overcome this they split supply between 2 meters - a “normal” meter for electricy used for lighting, cooking etc, and another meter for electric heating only. To do that however meant using a meter that could be switched on and off when the power company demanded it, hence the Dynamic Teleswitch Meter used in these tariffs.  There is a difference in some of these teleswitch meters - some are used “dynamically” when times can be varied and others are used in “dumb” mode i.e. times are set for example Economy 7.

The dynamic teleswitch meter meant that it could be switched on and off as required by using a signal from a BBC transmitter.  These signals from different suppliers were converted into codes by an industry operator and sent to the BBC for transmission. However the BBC have wanted to shut down the long wave signal transmitters for years as they use old valve technology and there are no spares!  The industry however, because they have not yet devised a system to replace it, have paid the BBC to try and nurse the transmitter into longer service and it seems that OVO are the biggest contibuters.  The latest effort is due to end in June 2025 after previous closure dates in 2021,2022,2023 and 2024 had to be extended. As you can see this issue has been known about for a long time, and OFGEM are now so concerned about the delay that they recently wrote to the industry to tell them to get “their finger out”

I can only speak of the THTC tariff as examples as I have been on this for 27 years as my house is all electric.  THTC allows, for storage heating, UP TO 12 hours supply in every 24 hours with a guaranteed supply of 5 hours depending on weather conditions e.g. heating times are longer during the winter months when it is colder. It allows the supply times to be varied throughout the day, depending on area demand, but most of the power is supplied at night with top ups during the day. Hot water is through 2 immerser heaters in the water tank - the bottom immersed controlled by the DTM but at differnt times to the storage heater supply, and the top immerser as a boost which can be switched on at any time but still charged at the “cheap” rate.  Electric panel radiators or electric fires (anything relating to heating your home apart from storage radiators) was also charged at the cheap rate at any time. You can see now why 2 consumer units were needed in a household - one for light and power and another for heating and hot water - as all the heating had to have separate controls.  Even the heating consumer unit had 3 separate supplies to it - one for storage only, one for 24 hour heating supply and the other for hot water.

That is the history of the dynamic teleswitch system, and it has been in use since the 1980’s, - it enabled suppliers to delay heavy investment in the distribution system and manage the load in their area. That has now came back to bite them in the bum - big time now that the radio signal needs to be switched off.

OFGEM says that smart meters have to be installed at no cost to the customer. It can be seen from the above history that putting a normal SMET2 meter in place with set switch off and on times would not solve the demand issue on the distribution system. It would also place the consumer with a cost to have their internal wiring re-arranged. To try and keep the original wiring, industry has been trying to come up with a 4 or 5 port meter  which would alleviate that problem but does not cover the load management issue.  DNO’s have been spending huge amounts of money over the last few years trying to upgrade the distribution system but that is still years away from being complete - if it ever will be.

Many consumers like the THTC tariff as it gives them the option of switching on their heating during the day at the cheap rate of the tariff. To others, THTC is now exorbitantly expensive as the cheap rate used to be 50% of the normal rate. Today that is not the case with the cheap rate being almost the same as the normal rate and these rates, because they are not “standard” tariffs, are not controlled as per OFGEMS price cap and suppliers seem to be able to charge what they like.  Many others look at “cheap” nightime rates from Octopus and others in single figure pence per kWh and wonder why they are being charged 22p per kWh for their cheap rate. Others cannot upgrade to green alternatives like PV because of the load managed are designation where they live. And so it goes on.

These DTM’s were brought in to save the  electricity industry money and were for their benefit, not the consumer’s. As Blastoise186 has stated earlier it is not a simple problem and it involves more than just OVO but the industry have known of the issue for many years.  It would appear to many that it is not a priority for them or they lack the expertise to come up with a solution (which I doubt).

I’ve heard that excuse for more than the last 3 years. Time to knock heads together and lock them in a room until a solution is found.

What is it that'll be done by June 2025? Do you mean the rollout of the new kit will be completely installed by June 2025? I've also been told the rollout was due to commence June 2024.

One of the Scottish issues is probably that currently the Shetland isles have a local diesel fuelled power station supplying elec to the islands population (23,000). No mains gas means mostly elec heating, to help the load demand on the local station a version of THTC was installed in many homes. A huge subsea cable is currently being commissioned to finally connect the islands to the national grid meaning the local power stn load management issues will no longer be an issue.

Hi All

Great explanation from metalsman - many thanks. External control of consumer goods feels a bit 1984 to me but then I suppose it was 1984 or thereabouts.

Anyhow, I contacted SSEN to see if they were placing restrictions on the THTC replacement from a network management perspective and they were adamant that they are not. One could argue “they would say that wouldn’t they” but I thought it was interesting. Moreover, I’m not aware that anyone is prevented from getting an EV in the region and installing a domestic charger running at 7kW when ever you like. If there really are network constraints how can this be?

Here’s an article that may be of interest if you haven’t seen it already.

John's switch from restricted to single meter wasn't easy | Home Energy Scotland

Sorry but I cannot answer for situations outwith mainland Scotland as some islands will be supplied by an undersea cable and others by an on-island supply source eg, wind farm, diesel etc.

As to distribution networks, this is split into high voltage (generally the lines on pylon towers) and low voltage (33kV or less) In the UK, high-voltage network substations are used to step down the voltage levels from 275kV and 400kV to 132kV for distribution. Intermediate electrical substations then reduce the voltage further from 132kV to 33kV and 11kV for transmission to final distribution substations. Here, the voltage is reduced further to the 400V or 230V typically used commercially and domestically. Which part of the system has the issues is, as Blastoise186 said, a closely guarded secret and not something we will ever know the details of.

I am in NE Scotland, one of the areas with the highest concentration of onshore wind farms in the UK. Now maybe I am a cynic (in fact I know I am one) and I also ask myself why, if we have so many wind farms, we pay some of the highest transmission charges in the UK.  I even look out on windfarms but I do not get the benefit of all the power that is produced. AND I also pay for them being switched off when the wind is blowing (hundreds of millions of pounds per year) when the distribution system cannot cope with the energy produced.

If only the general public were made aware of and took an interest in all that is going on in the electricity supply chain there would be an outcry. All the public see from politicians is the smoke and mirrors of “the Green Transition”. I have been researching this since 2010 when the coalition government started tinkering with energy supply and ended up loading electricity bills with the majority (circa 90%) of the cost of the new social and environmental schemes they introduced and foisted onto suppliers (ECO, FIT etc) and then customers. Gas users typically only saw 10% of the cost of these schemes onto their tariffs. Emails to my local MP were flying off laptops and dont get me started on about Ed Davey MP (energy minister at the time)!

Time to get off my soapbox!

What really gets me wound up is that I know people in my area that are on Octopus Agile tarrifs. Literally the ONLY thing stopping me making use of cheap low demand times to charge storage heaters is the idiotic metering system. 

https://agile-octopus.datafury.io/#pricing-table

I plan on getting the heaters replaced with an ASHP and as soon as that is done I will be demanding this idiotic setup is ripped out and you won’t see me for dust as I will no longer have anything attached to the second meter. I expect OVO to make even this as difficult and painful as possible.

I wasn't very clear, I was just pointing out that there's also a generation issue in Shetland that's stopping them junking THTC, probably a few thousand homes in Shetland stuck on THTC till Shetland is linked to the national grid.

They're about to switch on the Viking onshore windfarm in Shetland so there'll be 450mw coming down the subsea cable to mainland Scotland shortly!

I have a house in Aberdeenshire supplied by Octopus, elec tracker and solar export and I have full control to choose my supplier and tariffs. And then there's our small house in Shetland, THTC and locked to maybe 3 suppliers with tariffs that don't support modern efficient heating systems.

You'll be glad to know that once the subsea cable goes live UK (mainland) elec consumers will see a very small reduction in their annual elec costs as they'll no longer need to subsidise elec generation for Shetland consumers

Seen this previously. I've been told by OVO that when they install the new meter to replace the THTC setup they'll look to arrange to have the 2nd meter point reference de-energised and move me to a single meter point reference number to allow me to move to a single tariff. Hardly a 100% guarantee but I do have it in writing from OVO following a successful complaint to the ombudsman.

A friend of mine who lives a few miles from me has THTC and is with Utility warehouse (storage htrs removed so static meter reading) has just been informed they're shortly fitting a smart meter and removing the redundant meter for the storage heaters.

Does look like things are starting to move in the right direction.

When the THTC meters were installed, the distributor and the supplier of electricity were probably the same organization, in many cases the local Electricity Board. This all changed with the privatization of electricity distribution and supply, so now we have a hybrid system with regional distribution companies and national suppliers. It’s not surprising that there’s confusion over who actually owns the THTC meters and, more importantly, who is responsible for their management and operation.

Some customers have had success with persuading the DNO to take the initiative to having redundant meters and their corresponding MPANs removed; others (like @Infiltrator’s friend) have seen the supplier do the same. If the THTC meter is clearly not being used, this is a possibility, for example if storage heaters have been replaced by a heat pump. As far as OVO is concerned, having two MPANs for the same supply seems to create an automatic block on having a smart meter installed. Of course there may be other considerations, too, like in communications black spots or in areas governed by load management schemes.

Thank you for sharing your insights & experiences. It’s been a while since we’ve had an OVO update related to THTC, I’m going to see if I can chase up an expert in this meter type & see if there has been any progress or updates.

I’ll report back to this topic. 

What’s probably worth noting however, is something that both myself and @metalsman have been trying to make clear (thanks for the assist by the way, much appreciated!).

The stance we’re taking on the Forum is to try and avoid making promises that we’re not 1,000,000% confident about - such as whether you can simply come off of THTC anytime soon. We’ve opted for this because we don’t want to get peoples hopes up only to throw you off of a cliff later when it doesn’t happen - it’s much better to burst that bubble now and replace it with a new one “later” if that makes sense.

As it so happens, I was chatting to a couple of National Grid engineers about THTC today (as in their DNO engineers who used to be part of Western Power Distribution) since I’m able to do that from time to time, these guys work on the 11,000V substations and transformers as part of their day jobs, so they know what they’re talking about. Didn’t get tons of time per se, but enough for a quick chat. Please note that I don’t normally get direct access to these engineers - it’s literally just a one-off thing and I can’t just turn it into a free-for-all to ask whatever I want for hours on end. I can only get maybe 10-20 minutes a day with them for a few days this month and that’s about it (and I kinda want to make the most of that for more than just one thing!).

They also seem to be taking the same stance - much of the infrastructure stuff is considered sensitive info that cannot be shared publicly because of the risks involved. Likewise, they share the views that the infrastructure up north desperately needs to be upgraded before anyone can even think about permanently nuking THTC completely.

While these specific engineers don’t work up in Scotland, they know how this stuff works pretty well and the discussions I’ve had - while they can’t be posted here - has given me some new info that I can use to further my research in the background.