Can I go from two electricity meters to a single Economy 7 meter?

I’m currently with SSE but hope I can get an answer here as they have been taken over by OVO. I have two separate electricity meters, one for standard rate, and one for storage heater and hot water, the latter being controlled by a clock which gives two separate charging periods.  We don’t use the heater except for background (low rate is about 45% total usage) and I think Economy 7 would be cheaper.  Is this possible to move to a single E7 meter (smart if poss) and would there be a charge?  The whole system dates from the 1960s and so far as I know the only change has been two new meters a few years ago.  Picture of distribution board attached.



Best answer by Transparent 29 May 2020, 13:44

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Hey @johnlbrooks, welcome to the forum!


We’ve got a whole bunch of great experts on this forum that would be able to help you with any questions you have.


@Transparent is a very knowledgable ninja, and is currently on here fairly often - Transparent, would you care to give your 2 cents on this one?



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Updated on 03/11/21 by Jess_OVO


Hey @johnlbrooks - that’s an “interesting” historical electricity fuse-board!

Your initial question is reasonably straightforward, although there are some alternatives to consider.

But the photo raises some other factors which are worthwhile considering… particularly around the area of safety.


**Edited by moderator**

These complex metering set-ups with SSE can be discussed by contacting the SSE Complex Heating Team on 0345 071 7972. They’ll be able to advise on the possible solutions to replace the current set-up with a more standard Economy 7 meter.



2: Safety of the existing installation:

a; The larger silver isolator switch at top centre looks like the mains incomer. We wouldn’t fit that now. Your local Distributed Network Operator (DNO) needs to be asked if they could change this to the usual 100A Service Fuse.

If you don’t know who is your DNO, fill out your Forum Profile and I’ll work it out for you.


b; The green earthing wires are too small. They need replacing with 10mm² green/yellow wire and your earth connection (copper stake?) checked for compliancy. This requires a local electrician. I’m unsure if OVO would be prepared to change you to a Smart Meter unless you had adequate earthing.


c; Your only safety (earth-leakage) trip appears to be on the input to the fusebox feeding the storage radiators. There’s no RCD that I can see on your lighting/power circuits. As the house wiring is old, there’s an higher chance of faulty wiring which could cause damage, but fail to blow the fuse. Not good!

Personally I’d be asking a local electrician to quote for a new “split load” Consumer Unit. These come ready-built with two RCD (safety) trips and a range of MCB trips which replace the present set of fuses.


The Consumer Unit here has ten MCB trips of a mix of different Amp ratings. There is a wide range to choose from. This one I found on the website of the electrical wholesalers, TLC Direct.

Dear @Transparent 

Many thanks for your answer and I note your safety suggestions.  Unfortunately, I have realised that I left out a couple of facts from my original question.

I’ve marked up my photo with the wiring layout that was previously hidden.  The biggest omission is that (I have been told) we have 3-phase power that enters the board at the numbers 1, 2 & 3 in the picture.  Those are hefty copper coated wires. The grey and black boxes they enter are 100 amp fuses. To my uneducated eye it looks like phase 3 supplies the off peak system.  The heating is fan driven hot air through underfloor ducts from a single large storage block in the centre of the house.  The grey box under the smaller fuse box is, I think, a RCD for the lighting/power.

Does any of this alter your views.  Many thanks for your patience

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Thanks for the clarifications @johnlbrooks and I’m pleased to find someone else who draws on top of photos like I do!

You having 3-phase would account for the size of the isolator box for the house incomer at top-centre. I’m still unsure what is the function of the smaller silver isolator at top-left, but it doesn’t matter for this discussion, so let’s press on.

I’d left out a space in my earlier reply, which meant you couldn’t click on a link taking you to the Topic where @Nancy_OVO mentioned 5-terminal meters. I’ve now re-edited it above, but I want to repeat it again here because it just happens to be within a recent discussion about a house with 3-phase electricity!

For the sake of others reading this at a later date, in John’s photo above, his labels 2 & 3 are the two phases, each entering the top of a 100A Service Fuse. Label 1 is the neutral connection which eventually goes to the larger consumer unit (bottom-right) supplying the main house circuits.

Your ducted hot-air heating sounds wonderful. This is obviously not going to be replaced by few Dimplex Quantum storage radiators! So scrub that suggestion.

The “correct” way to do all this would be to have two separate 45A ALCS devices connecting your heat-storage block and your hot-water immersion heater respectively. Each could then be driven by the Kaluza Platform I mentioned earlier.

Those devices don’t yet exist. But the electronics could readily be derived from the existing V2G charger, currently being trialed in 400 homes in GB.

There are other relevant Topics to read here, such as this one about Load Shedding and ALCS, and ALCS control from SMETS2 meters.

What we really need is a new Topic here on the Forum where we can run such concepts past a senior manager at Kaluza.

At this point I tag @Tim_OVO and say: “the ball is in your court. please do what you can to arrange this!”.


And John, I’d like a bit more information from you please:

  • Fill out your Forum Profile so we have your basic background information
  • Do you have gas (grid-connected or in bottles/tank)?
  • Do you have any renewable energy sources such as solar panels?


Thanks.  Profile updated, have mains gas used for cooking, no renewable source.

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Sorry, I forgot to respond to the comment about the RCD for the main fusebox.

This may do what’s required of it… assuming it’s rated to trip at 30mA of current imbalance.

However, using a single device like this for the whole house isn’t a great way of providing a protection system which is “friendly”. As it’s presently wired, as soon as a faulty device gets plugged into a socket, the trip operates and plunges the entire household into darkness! :scream:

That’s why I was suggesting a split-load consumer unit as a basic minimum.

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Ah… we both responded simultaneously.

Thanks for the Profile information. I had (incorrectly) guessed that you were in Scotland based on the type of electricity supply and ducted hot-air heating!

I’ll have a think about the implications of you having gas, but no renewable sources (yet). The best strategy for future energy needs is to spread your usage across multiple devices/sources. I have a hot water cylinder with three different energy inputs for example.

Payback period is quite important at my age!  The main reason for wanting E7 is so I can switch supplier freely.  Having 2 meters means, as I expect you are aware, that I am stuck with SSE because no other supplier will accept a switch.

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OK @johnlbrooks so I’ll try to avoid suggesting strategies with a 20-year payback time! :wink:

Do you happen to know the current or power-rating for that central heat-storage block?

I’m wondering if it’s essential to retain two phases, or if it’s possible to run everything from a single-phase meter.


Secondly, you may not now be as “stuck with SSE” as you suppose. As a result of the acquisition, all SSE’s problematic sites have now become OVO’s responsibility!

If one of your existing meters or the time-clock were to fail, they would have to be replaced anyway.

Even if OVO used existing technology and installed one their approved 5-terminal SMETS1 meters, they are scheduled to be upgraded to SMETS2 functionality and migrated across to the National Smart Meter Network as of 28th June.

Thanks @Transparent, The heater is a Creda Comfortaire.  I’m slightly confused because according to the rating plate on the heater it is 5 kw off peak, 250 w on peak (which I guess is for the fan), but the service leaflet I inherited from the previous owner says that the minimum model Comfortaire heater is 6 kw!  I suppose we go with the rating plate.

I’m not sure exactly what you mean as to not being “stuck”.  I understand that OVO have taken over, but surely unless I get a single meter as opposed to two I am now stuck with OVO instead of SSE?

Thanks again for your interest.


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That’s interesting @johnlbrooks - so the Comfortaire has two separate electrical feeds; one for the heater element which is controlled by the off-peak time-clock, and another for the fan, which must remain “live”.

I’d be surprised if it took as much as 250w to run the fan and any associated electronics/sensors. I have a twin-fan MVHR (mechanical ventilation with heat recovery) unit, and that only draws 80w peak.

However, 5kW is pretty small for a whole-house hot-air system. I can understand why it’s fed from a timeclock to enable you to benefit from cheaper-rate electricity. But I have no idea why this would need to be on a separate phase!

To put this in context, most electric shower units would be rated around 10kW and we don’t insist those houses use 3-phase.

Creda is also now a division of Dimplex, who have licensed OVO’s control system for their Quantum Storage Radiators. I wonder if the controller could be made available as a retro-fit to your Comfortaire? You could try emailing them to enquire.

So my current assessment (pun intended!) is that you could ditch one of the phases and have an ordinary single-phase SMETS2  Smart Meter with an Economy-7 tariff.

Just be aware that it is common practice for customers with E7-tariffs to pay a higher-rate per kWh for their standard electricity. So E7 isn’t always viable.

And that’s why I think you might wish to avail yourself of a smart-tariff “layer” over the top of an ordinary tariff. You’d then be fed much cheaper electricity by the Kaluza Platform whenever it bought-in low-priced energy on the wholesale market. And as it’s got weather-forecast input, you’d only be fed enough electricity for the predicted demand over the next 24 hours.

I hope I’m making sense.

Just in case I’ve missed anything, I’m going to tag @PeterR1947 to use his engineering experience on the above recommendations, and correct me as required.

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Some great technical support here from @Transparent - @PeterR1947 will be about at some point this week as well. I’m sure he’ll have a look and see if we’ve missed anything. 


Those devices don’t yet exist. But the electronics could readily be derived from the existing V2G charger, currently being trialed in 400 homes in GB.

What we really need is a new Topic here on the Forum where we can run such concepts past a senior manager at Kaluza.

At this point I tag @Tim_OVO and say: “the ball is in your court. please do what you can to arrange this!”.


Sounds like a great idea for a topic - get this posted and I’ll make it into an article and share with my colleagues at Kaluza. Plans are in place for this already, an ‘Ask me anything’ with a Kaluza product manager. So @johnlbrooks get this suggestion in when that’s posted later this week hopefully!

Thanks @Transparent 

My system was installed in 1965 so I doubt whether any modern control system could be retrofitted.  But I could be wrong!

Very interested in your suggestion to ditch a phase and go E7 on just one.  From what you’ve said earlier I guess I’d have to pay for an ordinary E7 meter as the smart meters are not yet available.  Changing the supply to just one phase would cost even more I guess.

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@Tim_OVO@Transparent@johnlbrooks All, the suggestions are sensible, the distribution board is a typical 1960s nightmare!  As a first, I would suggest getting a local electrician to install a split load Consumer unit as @Transparent suggested; the earth wires should be updated at the same time.  You should expect to pay between £250 and £500 for this. At least, once that is done you can feel safe and deal with the meter problem afterwards.

I wonder now you get on with the warm air heating?  The reason I ask is that in 1965 I rented a house which had that sort of heating and it was fine until the thermostat clicked off when the house rapidly went cool!  In fact, the landlord had gas fired CH installed and the warm air system deactivated.  I’m not suggesting you replace the system, Just curious as to how you find it.

Hi @PeterR1947 

Thanks for your comments.  I’ll look into making the improvements.

We don’t use the comfortaire for main heating - that comes from a large log stove in the sitting room -  the thermostat is in that room and as we leave it set at 60 degrees (F) the fan (rather noisy) only comes on occasionally, usually in the morning before I’ve made up the stove.  We also use electric convectors and fan heaters according to which room we are in.

It’s on from Oct to May and provides some background warmth to the house and particularly  the kitchen/diner where the block is located.  I’ve actually never tried to use it to provide the main heat - the previous owner said it was inadequate so since we bought the house (1983!) we’ve used the stove for main heat.  Also, the ducts don’t go to two of the bedrooms or the bathroom. 

Total on and off peak consumption is about 12500 kwh/pa of which about 45% is off peak (includes hot water).

That’s probably much more info than you wanted!


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It looks like we’re all heading in the same direction at the moment, which is gratifying!

Let’s deal with a few of the easier issues quickly.


1: Although not ideal, it is possible to have an E7 tariff from OVO and use a standard 4-terminal Smart Meter. It takes the entire house onto the cheaper tariff for those 7 hours. That’s one reason why the standard daytime costs are higher than otherwise.

I’d prefer it to use a 5-terminal Smart Meter because that would lower the unit costs in daytime. But since OVO don’t yet offer such a tariff, we have little idea whether this is financially beneficial in your case.

And my best-of-all option would be to have a 4-terminal Smart Meter but with extra in-line Smart Switches controlled by the Kaluza Platform to run the immersion heater and the Comfortaire. That doesn’t tie you to any particular hours to have electricity fed to those devices.


2: Don’t worry that there are bits of the puzzle which don’t yet exist as a “final product”. The technology is already within the V2G charger and is also successfully running hundreds of those Dimplex Quantum Radiators across the UK.

We need to start that separate Topic and persuade Kaluza to put it in a stand-alone box. If they won’t do it, then there’s plenty of Far-East rivals who’ll be reading what I’ve posted here, and will be only to pleased to take Kaluza’s market from them!


3: It’s likely that the Comfortaire lacks the levels of insulation which we would now use to surround the ducts. That could be remedied piecemeal, depending on accessibility, and thus improve efficiency.

You now know I’ve got a working (self-installed) MVHR unit to which I still have further ducts to be added. I’ve installed a secondary heat-source in this, using a small (150mm square) radiator in the flow-pipe which is fed from the same water at 45ºC that gets sent to my underfloor heating (UFH) pipes.

I also have a vacuum-tube solar hot-water system. So if we get a cold but sunny day in mid-winter, my UFH and ducted warm-air are supplemented from the solar input.

If I’d bought a house with a Comfortaire like yours, that’s exactly the sort of strategy I’d use. Keep the ducts and add another heat source!


4: I suggest you send a email and make an initial enquiry as to having a Smart Meter and an Economy-7 Tariff.

Give the URL of this Topic so that they can read what we’re discussing.

Mark the email “For attention of SMETS Engineering Team” so you don’t end up with some terribly polite reply from an ordinary member of Customer Services who hasn’t a clue what 3-phase and 5th-terminal actually mean!

I think the costs will be much less than you think.

The Smart Meter is free. The Installer will have the 100A Service Fuses open anyway, and will simply  remove the wire which feeds one of them.

You could also have your local electrician there at the same time so they fit the new tails into a new split-load Consumer Unit.

I’m struggling to think why this should cost anything more.

Thanks @Transparent 

What a lot to think about!  The ducts are mostly under the solid floor so inaccessible.

Option 4 looks the immediate way forward and i’ll also contact an electrician.

Very many thanks.

I currently have 2 SSE meters. One is connected to the underfloor heating and one to the reminders of the domestic supply. SSE say they cannot provide a smart meter and yet refuse to give me the smart meter rate even though they cannot give me one. Can OVO assist please?

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Hey there @Jacki .

We’re really sorry for the slow reply and for the delay in getting your question published. inSided were having some technical gremlins with the spam filter that caused pretty much everything to be gobbled up. I’ve managed to summon help from the moderators to rescue your question and inSided have now managed to round up those pesky gremlins.

Sorry for the trouble!

As for your question, this is a really good one actually. I’m going to assume that you might have something like an RTS Meter setup on a tariff like Total Heat Total Control. In which case you might also want to check out these threads: 

If you’re OK with this, could I also ask you to snap a few photos of your meters, consumer unit/fusebox, heating and hot water systems and pop them in your next reply? Given the complex setup, having a few snaps can really help us to offer the best advice we can.

The best advice I can give here, would be to see if you can get that second meter ripped out so that you’re back to a more basic setup. SSE should be able to do this but there may be a charge. I’m not sure if OVO has now started to be able to handle this setup directly, but I can confirm that @Tim_OVO will stop by when he’s free.

Just so you know, asking for help here is completely free of charge, even if you’re not with OVO. Please do feel free to ask for as much help and advice as you need - this sort of meter setup is not something that’s easy to untangle! I’m really glad you’re asking for help with this before making any moves, because switching unusual meter types can be a headache.

If the existing position remains true, then you’ll likely want to have SSE rip out the second meter for now and put everything back to a One Meter, One MPAN setup. This would also get rid of that pesky second standing charge. This would also allow you to switch freely to any supplier of your choice, without the hassle of towing two “Related Meters” with you.

From here, you’d be able to switch to OVO freely and take on a tariff such as Better Energy or Better Smart Energy. If you’re planning to get smart meters anyway, the Better Smart Energy tariff is the one I’d recommend here. It also supports Economy 7 in case that helps.

However, it might be possible for OVO to take on your supply as-is for now and then help you to get the existing meters replaced with a single smart meter. If that’s the case, signing up with OVO directly and then sorting the meters out could work. I’ll need to get Tim to double check first though.


Hang in there and we’ll definitely see what we can do!

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Wow you’re good, @Blastoise186 


Hi @Jacki and thanks for posting this. I’ve moved it over to this topic thread, as it’s very similar. @johnlbrooks was also with SSE with two electricity meters. We might hear from them about what happened in the end. 


As @Blastoise186 mentioned, usually getting one of the meters removed is the way to go. Also see the ‘best answer’ (at the top of the thread) for more info and advice. 


A picture of this meter area would be really handy! 

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It’s also important to note that SSE has started the process of phasing out legacy meter types and I believe pretty much all of them are entering the End-of-Life/End-of-Service phase of their service lifecycle. SSE has also confirmed that the tariffs related to such meters are also being shut down soon.

Given that it’s very unlikely that you’d have one of these unusual legacy setups unless your supply has been on one of those tariffs with either SSE or an equivalent one elsewhere at some point, it’s disappointing that SSE are refusing to try and help you get this sorted out. I’d be willing to bet that if @Tim_OVO was to look up the MPAN for such meters on ECOES, there would almost certainly be something on there which might flag up the fact the certification is due to expire soon. Suppliers are supposed to replace meters when this happens.

It does seem a bit negligent for a supplier who installed loads of these meters back in the day and has made it clear of the intent to replace them, suddenly turns round with a “computer says no” scenario.

Hopefully, getting this sorted out shouldn’t be too difficult though, and once you’ve upgraded to a meter setup that’s not as messy, you shouldn’t have this sort of trouble again. If you’ve got Related MPANs, that could cause a snag as mentioned over here (might have been fixed since!).

However… I don’t think that same snag applies to two meter, two MPAN scenarios. But I guess the easiest way to see whether OVO can handle switching these over, would be to give it a go and see what happens. If the switch goes through successfully, OVO should then be able to work on sorting the meters out after you come on-supply. If it fails and bounces back to SSE, you’ll need to convince SSE to remove the second meter first.

Since you can only select the Better Smart Energy tariff when you first sign up with OVO and don’t already have a smart meter, I’d recommend going with this one rather than the usual Better Energy tariff. Since you’ll probably want to replace the existing meters anyway, it makes sense to take advantage of these offers.

Thank you for all your helpful comments. Clearly, the best solution is to change to one meter.

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I have just inherited the problem of 2 SSE electricity meters have recently moved home. There is some useful information on here but i wasn’t clear how to go about moving to 1 meter - can i get SSE/Ovo to do this and install a smart meter or do i need to employ an electrician to convert the meters to 1 meter. Thanks

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Hey there @Ray780 !

You won’t be able to get an electrician to do this, so it’ll have to be your supplier - most likely SSE unless OVO is listed as the active supplier. Could you show us some photos of your meters please? This will definitely help us figure out what you’ve got so that we can give better advice.


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Thanks for the reply and I’d be hugely grateful with help to resolve this. I attach a couple of photos which illustrate the set up which are located in the garage. One of the meters seems to have very low usage whereas the other one seems to be the main meter.