The meter should be configured to switch power to the storage heaters on and off at the same times as the tariff changes from peak to offpeak and vice versa. it looks like this may not be happening. Where does MIL live (town and county, or first part of her postcode is enough)?

Are you able to get photos of her meter? This should help us make reasonable suggestions.

• Press a button on the meter to light up the display if necessary, then take a close-up of the meter so its display and all its markings are clear and legible. Note the time when the picture is taken;
• Move back and take a photo of the whole backboard to show all the equipment mounted on it, the cables from the service head (at the end of the main supply cable to the property, incorporating the main fuse) to the meter and the ones coming from the meter towards the consumer units;
• It might help to have photos of the consumer units themselves with the lids open, again clear enough to be able to read what each breaker is for (assuming they’re adequately labelled).     

Hey ​@david.sinc100 

Sorry to hear about this.

One of our volunteers has left some really helpful advice here already. If you could follow the steps above and provide the photos, we’ll hopefully be able to help better.

We’ve got a couple of similar topics that may also be helpful:

Keep us updated with how you get on, and if you can take those photos that would be helpful.

Thanks very much for your advice.  She lives in Perthshire.  I'm attaching a few photos - hope they give an idea of the set up.  The cables from the new smart meter have been labelled.  The storage heaters (and water) seem to relate to the lower of the two consumer units but I can't see how the cables connect in as they all seem to feed into the top consumer unit.  Thanks again for your help.

Thanks for those lovely clear pictures. I wish I were an electrician, so I could work out what’s going on.

The Domestic economy plan is an extension to the well-known Economy 7 (E7) arrangement. It allegedly gives eight offpeak hours, from 23:30 to 07:30 GMT (so an hour later during British Summertime). Surprisingly, it appears to have lower unit rates than E7. Your MIL should have had a confirmation of the tariff details after the meter exchange, so that’s where you’ll find the offpeak times and rates. If you have access to her online account, the details should be on the Plan page.

Now, the meter has two line feeds coming from it, labelled LL and LLL. LLL is the one that should be powering a separate circuit for the storage heaters and the water heater. There is a time switch - called ALCS - inside the meter that should activate this circuit only during offpeak hours. All usage - for whatever purpose - during offpeak hours is charged at the offpeak rate (currently 17.24 p/kWh, if I’ve read the tables correctly). All other usage is at the peak rate, currently 28.40 p/kWh (same proviso). 

The problem with high peak usage may caused by other heating equipment, like the panel heater(s) which would normally be run as necessary during the day at peak rates. This is a departure from common THTC arrangements that may have preceded the meter exchange; these usually incorporated a 24-hour heating circuit, charged at a lower rate than other domestic stuff like lighting, cooking and washing. Could it be that MIL has to top up the warmth from the storage heaters by direct heating? If the storage heaters aren’t up to the job of keeping her warm all day - which isn’t unlikely - then it could be that ‘Domestic economy’ isn’t the right plan for her.   

The next thing to check is that the storage heaters and the immersion heater are only taking power during offpeak hours. If this isn’t obvious (e.g. from a red lamp at the heater showing that it’s charging up), it should show on the meter itself. At 23:30  (if that’s the right start time) or shortly afterwards, the little icon in the bottom right-hand corner of the meter’s display should change from open (o´o) to something else. What it shows depends on how the ALCS is wired up inside, but it will be either closed (o¯o) or something like LC1 - it doesn’t matter much what it shows, so long as it’s not open! The reverse should happen at 07:30 or soon afterwards, when the offpeak period ends. I realize that this may sound daunting to an elderly lady, but you may be able to persuade her to give it a go.  

It may be that you’ll have to spend a bit of time with her working out what is using electricity and when. She should have been given an IHD when the meter was installed; this is a useful guide, if it’s used to show how much power is being drawn at any given time. Boiling the kettle, for example, will normally cause an IHD to show red, with a ‘using now’ figure of something over 3 kW. After switching the kettle off, Using now should drop to much less - of the order of 100 W.  

One last question - do you know what the Pulsa circuit breaker (the one next to the main switch in the top CU) is connected to? Is there perhaps a ‘heat store’ in the flat? 

MIL is lucky to have someone to help her through what is sadly a bit of a jungle. The change from an RTS-controlled THTC arrangement to one managed by a sophisticated smart meter will rarely be straightforward, because the number of factors involved is unbelievable, and they’re different in every case. It’s not at all surprising that not every exchange is seamless.

Along with the detail noted by Firedog, it’s worth concentrating on the wiring on the centre white block in the last image 

There seem to be guides to connections written on the cables and one says hot water, the other heat tima (?).

If the hot water is connected via this then it is fed from the off peak circuit but might also have boost feed to top up during the day. Another suggestion is that there may be an external timer which has gone ‘out of sync’ after having power off for a while during the meter swap. 
There are several other checks which could be made, isolating circuits via the switchboard to isolate any rogue items which are connected on peak instead of off peak. 
The right hand white block has cables labelled 24 which suggests they are connected to items ‘on’ through the peak period .. worth another check. 
Or it could be a simple state of the meter having peak and off peak reversed. 
Hope it doesn’t take long to resolve 

Thanks, ​@BPLightlog 
  

I’d decided it just says HEATING - it’s not easy to write clearly on a surface like that 
  

The one on the left of the lower CU is labelled Immersion.  I took this to be the secondary, upper, boost immersion heater in the water tank. It’s switched on here; perhaps there is a boost switch by the tank which should normally be off, but may of course be on. If it is, this will be very wasteful; the tank should be up to temperature in a couple of hours or so even from cold if it’s being powered overnight, so there should only be a need for boost if MIL has a deep hot bath before washing up …

That said, it wouldn’t be unusual in a 20-year-old installation for there to be a clockwork time switch near the tank, which needs checking on every so often to make sure it’s showing the correct time (at least twice a year at each end of summertime). The clockwork will only run while the power is on, so it can easily slip as months go by. It’s not really necessary now that the meter is switching the main immersion heater on and off at the appropriate times, but it won’t do any harm so long as the boost isn’t always on.

Any ideas on what Pulsa might indicate? Perhaps I’m just suspicious …
  

At any rate, ​@david.sinc100, the water heating control arrangements need a special inspection. We often see this as a cause of ‘too much electricity consumption’.

I’m not sure it says that although I can’t quite resolve it by sharpening. 

The thing I’m mostly suspicious of are the cables labelled 24 which are connected via the peak circuit. 

There are other ‘heating’ options indicated on the other switchboard 

Including a ‘Panel Htr’ as you suggest. 

It may be a Pulsacoil hot water system?

Edit- link changed for a better one:

http://www.gasapplianceguide.co.uk/Gledhill%20Pulsacoil%20explained.htm

Note the diagrams, with both peak (boost) and off-peak immersion heaters.
 

Interesting, so hot water heating ‘on demand’ but presumably on a large scale if it copes with a whole household demand

I have to admit that I have never come across one of those before.

In this case then if the CU’s were set up as one for peak and one for off-peak that could explain why there is a ‘Water heater’ in both, one for each immersion unit.. (and for some reason called ‘water heater’ in one but ‘Pulsa’ in the other).

I guess that we need ​@david.sinc100 to confirm if there is one of those Pulsacoil water heaters?

If it is indeed ‘heat store’ as I suspected, then that is bound to be a real glutton for energy. For it to work effectively, the water in store must presumably be kept at a higher temperature than the 50-60º of an ordinary tank if the heat exchange mechanism is to work properly. It may well have been relatively economical with a 24-hour low-rate supply like that provided by THTC, but I could imagine it being ruinous if it has to operate at peak rate to work as intended. I see that some allegedly work with Economy 7-type tariffs, though.

I was hoping to be able to show a comparison, but the prices tables are apparently under construction in anticipation of tomorrow’s price-cap change. If my notes are accurate, the heating rate under THTC was 22.42 p/kWh, while the peak rate under Domestic economy is 28.40 p/kWh. 6 p/kWh would soon mount up if the thing is running during the day.

There should be a seperate ‘boost’ switch for the on-peak immersion coil so that it isn’t active all the time.

However I’m wondering if the setup in this case is missing a timer, which will be needed now that the supply has been changed to E7?

Here’s some wiring diagrams for different tariff setups from the installation manual for the latest model, which all show a boost controller on the on-peak heater.
Click the image on this page for a pdf of the manual: http://www.gasapplianceguide.co.uk/gledhill_pulsacoil.htm

The second one says it would be applicable for E7, note that it has a seperate timeswitch.

However if there is one of these heat stores fitted then it may have originally been wired as the first diagram, and the meter itself should be doing the switching to mimic the old supply.
If the meter isn’t doing that switching then the off-peak coil would be heating 24/7.