Total Heating with Total Control (THTC) - OVO/SSE ending support in March 2023

OVO has announced that it is ending support for THTC in March 2023 (after having taken over part of SSE) so the radio controlled operation of “passive” storage heaters and hot water will no longer be available. There is also a knock on effect to focal point fires, showers, towel rails and panel heaters. Since OVO is actively changing how a THTC system was originally designed then should OVO simply change only the meters and leave householders with the legacy of old heaters or should OVO change meters and provide, at no cost to the householder, new, up to date storage and panel heaters with inbuilt timers so that householders can control their heaters?


Best answer by Tim_OVO 19 April 2021, 11:52

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Hey there @cgzovo !

I’ve actually written a guide about the RTS Shutdown previously, which you can find at 

However, I didn’t include this particular question at the time, since I didn’t have any info for it. I’ll aim to update my guide once this thread has a suitable answer.

I have to admit that this is a seriously good question, which definitely deserves a good answer. As a forum volunteer, I can’t speak “officially” on behalf of OVO, but I can give my own thoughts and advice. No doubt other members here might have some thoughts as well. I’ll try to catch @Tim_OVO as well for some insight as to any policies.

OVO never offered RTS meters/tariffs themselves, but has technically inherited a fair few via various methods like the buyout of SSE’s Retail Division.

It’s a really, really complicated matter, but I’m not sure any supplier would be willing to rip out and replace everything else beyond the meter free of charge because anything beyond the meter is your own responsibility. This is a huge topic though and I don’t have enough time left on my lunch break for a detailed reply, but I’ll check back later. :blush:

The best that I can think of which a supplier might do, would be moving affected members over to a tariff such as Economy 7 and attempt to hook up things like storage heaters to the Fifth Terminal on the new smart meter, in order to control their operation and have them only come on during the cheaper hours. Everything else may have to be reconfigured back to the “regular” supply and run at the normal rates for the time of day. You may also need help from an electrician in order to sort out the wiring.

Great article! I would say this about OVO - they knew what they were taking on at the buyout of SSE Retail so there can’t be any excuses about legacy THTC systems. OVO will offer Economy 10 or 9 but this is effectively still locking in to OVO as a supplier as it is notoriously difficult to change suppliers with this setup or at least drastically reduce the potential competition for switching. Everyone has a right to change their supplier without constraints and therefore OVO must allow householders the choice of a single rate supply or Economy 10/9. Not everyone would want legacy storage heaters heating (burning a considerable amount of electricity) in the afternoon for example as the latter choice would do? Because of OVO’s action to end THTC then it must upgrade a passive, out-dated heating system to suit by giving the householder full, individual control of every heater.

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I hear you there @cgzovo , but I also have a few things that I may need to correct you on and provide more context with.

Firstly, I can assure you that while OVO never planned to offer any kind of legacy RTS meters or legacy tariff types that go along with them, the company is attempting to work on a migration path that would move affected members onto more appropriate meters and tariffs - and these would make it much easier to switch suppliers if desired. Likewise, all the other suppliers are trying to figure it out as well. No-one wants to lock customers in like this, but the challenge is to figure out how to unlock the padlocks and remove the barriers. OVO merely inherited this issue when they bought SSE, but SSE isn’t fully integrated into OVO right now, so it still runs somewhat independently for the time being. The decision to end THTC was made by SSE before OVO bought them out, but it wasn’t really announced at the time.

In theory, there are ways to migrate heating systems that were controlled via RTS Meters to Smart Meters, provided they’re all wired up properly. Five-Terminal SMETS2 Smart Meters exist for this exact purpose. However, OVO can’t go about replacing equipment that was never installed by OVO or even SSE - they’re only able to replace the equipment that comes in scope. There’s more info on this in @Transparent ‘s excellent guides over at 


I appreciate it may not sound like the answer you’re after, but I’m only a forum volunteer who helps out here, rather than a paid OVO employee, so I can’t make changes. However, I also know that OVO has a duty of care to their members, so they wouldn’t just rip out the RTS Meter without thinking about how to get your storage heaters and hot water to work properly in the future.

I’ll see if @Jess_OVO and @Tim_OVO are around for advice though. They might know more than I do.

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Welcome @cgzovo and thanks for asking a great first question!

As ever @Blastoise186 has raised some excellent points in relation to the implications of  OVO taking on your type of meter setup. We’ve taken this one to the relevant team so will pop back with an official update  soon...

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Thanks @Jess_OVO !

Yeah, the ultimate problem stems from the fact SSE are being forced to terminate legacy RTS based tariffs like Total Heat Total Control - just like all other suppliers - because the infrastructure that used to power the Radio Teleswitching Service is shutting down soon. Even if ANY supplier wanted to keep it going, they can’t because it won’t be there anymore. Once Arqiva flips the off switch, it’s game over for the entire system. In some ways, SSE didn’t actually make the decision to withdraw THTC, since it relied on external factors beyond their control.

The only feasible solution is to replace ALL of these legacy RTS Meters with more modern smart meters and reconfigure all the wiring to something that’s not quite as messy or tangled up in spider webs. Given that the vast majority of RTS Meters are getting pretty old and will be up for re-certification soon, they’ll all need to be replaced soon anyway, even if RTS wasn’t shutting down.

There’s also no realistic way to simply update legacy RTS Meters to use some other signal because (unlike smart meters), it’s impossible to do any kind of software/firmware upgrades to the Radio Teleswitches that control such meters - it was never part of the spec because the concept of software updates didn’t really exist back in the 1980s.

It’s something that I’ve been researching in the background over time and raising awareness of. But it’s also one of the reasons that OVO has never offered these kinds of tariffs and meters. By the time OVO was founded, the trend was already slowly starting to shift away from RTS, so it wouldn’t have made much sense to join the party so late.

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Updated on 27/04/22 by Jess_OVO


You might have already heard that over time, all SSE Energy customers will be moving to OVO Energy. We’ve made FAQs on this here. To make this as smooth as possible, we’re looking to move everyone across gradually. We’ll provide updates every step of the way. The move won’t interrupt supply, or affect prices.


If you haven’t heard from us yet, it means you’re staying with SSE for the foreseeable, so you’ll still need to contact them to discuss your account and the plans available with your current meter setup. The SSE complex heating team can be reached on 0345 071 7972


This page is also really worth a look:


I’ve actually written a guide about the RTS Shutdown previously, which you can find at 



SSE have also outline here, that their support of this tariff and meter system will end soon, but they’ll reach out to you directly to discuss a smart meter system replacement that fits your needs. 

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As we know THTC is becoming defunct. I live in Aberdeen and have been on THTC for some 25 years. In the past my method of operation has been to use the storage heaters to provide a basic level of heat and “top up” by using panel heaters (24 hr supply) all at the same price per unit.

What are the replacement options?

ECO 7 - traditionally this was not considered long enough to charge the storage heaters up here without an afternoon boost.

ECO 10 - This sounds promising but the websites say this is not suitable for storage heaters only for wet electrical systems - why?

Any other options?  How do I evaluate the ECO 7/10 tariffs when I do not know the split between storage heater kWhs (night rate) and panel heater kWhs (day and night units) from my THTC meter. In the last year I used 1550 kWh on standard and 16800 on THTC. I also have 1.5 kW of solar linked into my standard consumer unit. Does this affect the decision?

At present the THTC meter contols when the storage heaters and water heating are charged. If SSE change my meters to ECO 7/10 does this still happen or would I need a time clock on those circuits? I presume the new meter would be a smart meter!

I tried talking to SSE Energy Heating but they only confused me more by assuming I understood what they were talking about!!!

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Welcome to the forums @dpinches !

This is definitely going to be a hot topic, so I’m really glad you stopped by. I suspect you may be aware of the reasons why THTC is ending, but I’ve also got some FAQs that might help.


The best advice I can give is that yes, you would have the meter replaced with a smart meter and it would be capable of running in at least Economy 7 mode with the ability to control your storage heaters and hot water. As with THTC, this would ensure they only come on during the cheaper rates. However, it would not be based on weather forecasts. As smart meters come with their own sort of built-in time switch, you wouldn’t need a separate one. This also makes things much easier in future.

As for what the best tariff could be, this is actually something that’s pretty complicated. Your solar panels could come in handy though, as you can still use any generation from those to offset some of the bills, just like you do now.

Could you show us some photos of your entire setup please? Knowing what you’ve got can make it easier for us to offer advice, so it would be great if you can do that. We’ll definitely see what we can do as well!

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I’ve also just started looking into a few resources I’ve got on hand, but this topic was moved mid-draft, so I had to submit what I’d put in my previous reply and carry on separately.

Having looked at Economy 10, the snag with that setup is that you can’t get a solid seven hour overnight period on the cheaper Night rate. It’s more like three blocks of three to four hours each day. That’s probably not going to allow sufficient time for storage heaters to build up enough charge. While it would probably get some charge in, it’d run out too quickly.

For Northern Scotland (MPAN Area 18), the times for Economy 10 offers four hours overnight, three hours in the morning and three hours in the afternoon at the cheaper rate, rather than the non-stop seven hour block you’d get with Economy 7. It would be very impractical to try to juggle this with storage heaters.

The other complication is that THTC allowed for certain other appliances to also run on the cheap rates 24/7, which doesn’t exist in the tariffs that are offered these days. This is where it really gets confusing.

It may be worth seeing if other options exist for heating that don’t involve storage heaters, but this is definitely something that’s going to need to be handled carefully.

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I’m still digging into some resources to see if I can gather more info, but it’s definitely looking as if it’s going to be very much case-by-case.

Thanks for providing the details so far though @dpinches . I’m going to continue by disregarding any electricity that was consumed which came from your solar panels. This sort of thing wouldn’t register on the THTC meter anyway as it only tracks what you import from the grid, so at least I don’t have to calculate how much to deduct for that.

To be able to attempt to calculate the split in your case, we’d need to know how powerful each of your heaters are and how many you’ve got, such as five 1KW Panel Heaters and three 5KW Storage Heaters. It would also help if you can give us an idea as to how you use them, such as how many hours they’re all used each day and if there’s any months where it’s all shut down.

The final one for now, is do you have anything else hooked up that can run on the cheaper rates? Once we know these details, we can certainly try to do some number crunching and see what we get.


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Having looked at Economy 10, the snag with that setup is that you can’t get a solid seven hour overnight period on the cheaper Night rate. It’s more like three blocks of three to four hours each day. That’s probably not going to allow sufficient time for storage heaters to build up enough charge. While it would probably get some charge in, it’d run out too quickly.

For Northern Scotland (MPAN Area 18), the times for Economy 10 offers four hours overnight, three hours in the morning and three hours in the afternoon at the cheaper rate, rather than the non-stop seven hour block you’d get with Economy 7. It would be very impractical to try to juggle this with storage heaters.

Before I detail what heaters I have and when I use them I would ask for more explanation re use of storage heaters on ECO 10. On ECO 7 the storage heaters would get 7 continuous hours of charge while on ECO 10 they would get 10 discontinuous hours of charge. Surely 10 hours is better than 7 hours for Northern Scotland. Doesn’t each charge period add onto what is already in the storage heater?  I do not understand!

I attach photos of the “power station”  - whole, left and right:

Incoming 100A fuse on left, standard rate meter with iBoost sensor and domestic isolation switch feeding consumer unit. The iBoost diverts any unused generation to the water heater instead of exporting it. This only occures when the Rayburn is not functioning in the summer.

THTC meter in centre feeding two storage heaters fuse boxes (left and lower right), off peak water heater fuse box and 24 hour supplies fuse box (panel heaters; water heater boost; shower unit and bathroom electric towel rail (1.8kW) and bathroom underfloor heating. Also solar panel isolation switch with generation meter below feeding ito consumer unit.

In addition we have a very old oil fired Rayburn stove in the kitchen. This heats the kitchen, provides background heat throughout the house, provides some cooking (we also have an electric cooker) and heats the hot water. It runs 24/7 but is turned off in the summer as it gets too hot in the kitchen!

We have a wood burning stove in the lounge.

Electric heaters:

Lounge:  2 off  4.5kW storage / 1.5kW panel combination units. Storage heaters not used. We use the wood burning stove in winter and the panel heaters  when not so cold.

Office:  1 off  4.5kW storage / 1.5kW panel combination units. Storage heaters used in winter and the panel heaters  when not so cold.

Dining room/Wine Cellar: 1 off 1.5kW panel heater - not used.

Inner Hall:  1 off  4.5kW storage heater used most of the year, turned off in summer.

Outer Hall: 1 off  2.5kW storage heater used only in winter.

Bathroom: Large 1.8kW towel rail. Underfloor heating - this only uses 1.5 to 3 kWh per day due to the towel rail being on.

Kitchen:  1 off 1.5kW panel heater - only used if problem with Rayburn.

Landing: 1 off  2.5kW storage heater used only in winter if temp drops below zero.

Bedrooms: Panel Heaters - not used.


If you need more just shout.


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Thanks @dpinches .

As much as it would be great for Economy 10 to be like Economy 7 but with a couple more hours added onto the overnight block, unfortunately that’s not how Economy 10 is designed. It only does the three periods a day arrangement regardless of supplier.

You are correct though. Whenever a storage heater starts charging up, it can top-up any leftover charge that wasn’t used up and combine it with the new charge while it’s running. If you’re careful, it may be possible to juggle this. But it wouldn’t be easy.

But I do agree that it’s still not ideal for where you are. I’ll see if @Tim_OVO and @Jess_OVO can find out whether there’s any plans to help with your use cases.

I see you’ve got a huge amount of equipment there as well. Upgrading definitely will need some planning. It’s also going to take some time to try and run some numbers, so I’ll see what I can figure out and update you soon.

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Ok, I’m going to take a first attempt at figuring out the numbers here. I could find an easily available tool that can factor in everything at once, so I’ve gone ahead and used RapidTables. I’ve used this tool before for cybersecurity related crunching, so I know it works.

Firstly, all the storage heaters combined. For anything you’ve mentioned that doesn’t get used at all, I’m disregarding those completely on the basis they’re using zero kWh anyway.

On the basis that all of the ones you do use run for five hours per day, their combined usage would be around 65kWh a day, 1950kWh a month or 23725kWh a year. On the other end, if they’re on for 12 hours a day it’d be 156, 4680 and 56940 respectively. This doesn’t factor in having them off in the summer though for example.

Likewise, with a combined 9.3KW, I calculate all the other heat sources (except the Rayburn) to be using 223.2kWh a day assuming 24/7 operation. Which also works out at 6696kWh a month or 81468kWh a year, again assuming 24/7/365 operation. Halving that gives 111.6, 3348 and 40734 respectively.

I think it’s probably safe to say that this might give at least some idea of the split. But a combined 288.2kWh a day is an awful lot of eco juice to pull. You’ve basically got a collapsed sun just in heating alone!

It’s getting late for me though, but I’ll pick this back up when I’m next on. 

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That’s quite the setup there, @dpinches which our resident number-cruncher @Blastoise186 is so helpfully trying to untangle.


As a similar THTC question was asked recently we’ve moved your thread here, so check the best answer above for our advice on this one. 

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Yep. This is not easy to figure out at all.

And in fact, when I attempted to crunch the numbers again just now, I got a pretty shocking result out of the calculator.



I think you can already see exactly why it’s impossible to run storage heaters on a single-rate tariff. This doesn’t even factor in any other usage or standing charges either!

However, with that being said… In certain cases upgrading to a smart meter may result in getting rid of a second meter (and a second MPAN), which would claw back some costs by the reduced Standing Charges. Multi-Meter setups carry one Standing Charger for each meter, even if they’re for the same supply. THTC just so happens to be a tariff that comes with two meters. And it looks like all of your meters might be (over)due for re-certification…

Hmm… This is a tricky one...

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I see what you mean!

Let me try and put together an Excel spreadsheet of when and for how long the heaters are used. I can then tweak the assumptions until the total consumption gets near reallity. Then looking at when the units are on during the day I might be abe to estimate the ECO7 or ECO10 consumption.

I would value your opinion on the spreadsheat when I produce it. Not sure I can attach it here or as a private message or how I can get it to you.

I will work on it!!!!

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No worries. Unfortunately, it’s not possible to upload files here. But there’s possible workarounds. It might be possible to enable though, but I’d need to ask Tim to grant the right permissions.

Once it’s ready, feel free to send an email to with the spreadsheet as an attachment. Make sure to mention that it’s for this thread and I think Tim might be able to upload it back here or figure out a way to make it accessible.

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I’ve just picked up the spreadsheet that Tim relayed over. I’ll take a look shortly and provide an update. :)

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Sorry for the wait here @dpinches . I had some other stuff over the weekend that took up all my time, so I didn’t get chance to review everything.

Your figures definitely look good to me. So from here, it’d mainly be a case of figuring out the next steps.

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Thanks for your help. Based on the figures I will apply for a change to an ECO 10 tariff and get SSE to change out my meter.

“but they’ll reach out to you directly to discuss a smart meter system replacement that fits your needs”   But what if I don’t want a smart meter in my house? What are the options?

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Hey there @Caroline11 .

I'm afraid your options would be extremely limited and smart meters would be the only path forwards once the RTS Service eventually terminates. RTS Meters are no longer installed for any site that doesn't already have one and the remaining stock is primarily being used as spare parts to replace faulty meters with. While the service is currently being maintained until everyone can be migrated off it, there's ultimately only a finite lifespan remaining before the BBC pulls the plug on the BBC Radio 4 Longwave signal that the RTS Service relies upon. This also affects THTC meters as well.

I'm afraid that there's no other meter setup that can replace an existing THTC Meter and still retain the same functionality either and a smart meter opt-out can technically be overriden by the supplier if the meter exchange is required in order to continue supporting the tariff you're on.

Is there any particular reason you don't want smart meters?

Thanks for the reply. Yes, there are just a few reasons I won't be having a smart meter.  This is the notice I sent to my energy supplier when smart meters where first introduced years ago      You'll find plenty of evidence of adverse health effects of radiofrequency radiation if you look for it.      

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I see. It seems you’ve been caught by a few myths actually and I am aware of those websites. While that particular opt-out notice is potentially valid for turning off marketing regarding Smart Meters, it’s not valid for all the reasons that a Smart Meter upgrade may be performed for. This is one of them.

You shouldn’t rely on those sites as they’re extremely biased as well. A much better one is SmartMe which is a lot more neutral. A lot of the anti smart-meter campaign sites use scaremongering and other falsehoods to try and sway your opinion. Smart Meters do not cause any more health risks than the computer or smartphone that you used to post on this forum after all (in fact, the radio emissions from a Smart Meter are even less powerful than a mobile phone).

Also, if you want to opt-out of Smart Meters, sending a notice like that one is not the way to go anyway. You should just tell your supplier by phone as that’s all that’s needed.

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In actual fact, while I'm not a lawyer and this isn't legal advice, having read that opt out letter again I'm tempted to call it out as invalid. In the UK, your energy supplier will not just randomly come round and replace the meters without your knowledge and over half the claims it makes are either untrue or questionable at best 

The website also appears to have been abandoned two years ago and doesn't appear to be actively maintained anymore. Not a good sign for such a campaign to randomly disappear from the radar without a trace. Its tempting for me to backorder that domain and redirect it somewhere else once it expires, but alas that's not something I do.

I should also probably mention that the meters are the property of your energy supplier and you have no ownership rights over that equipment whatsoever. If the meters need to be replaced for safety reasons or due to a fault, any smart meter opt out requests can be ignored, especially if the supplier doesn't have any traditional meters remaining in stock.