Unexplained half-hourly usage pattern

Thanks ​@Firedog I will see what I can dig up. 
 

Smart Meter was installed at Mums in early March 2026 (not quite two months ago)

Was it a non-smart meter before and she sent in readings monthly?

If that is the case then the usage figuers since the new meter was fitted are consistent with the usage figures from the previous meter.
Which is interesting and shows that although they look high for a single person they are probably correct if the heating is all electric and particularly if fan heaters are in use (all night?).

You still haven’t explained why there is no usage from before April 2025 showing.
Was she perhaps with a different supplier before that?

It’s now looking more like the meter is correct and your mum is using that much electricity, so why the half hour usage figures are not showing that correctly overnight remains a puzzle.
Could it simply be a case that the half hourly data is being recorded and sent to DCC, but that bar chart is not showing it correctly for some reason?

I think we are at the stage where some photos of the meter, and everything around it on the backboard, plus photos of the consumer unit, might be handy if you can provide them.

EDit- I just had another thought.
Is your mum perhaps on Economy7 tariff, and it’s the 7 off-peak hours that are not being displayed on the bar graphs that you screenshotted?
I’m not sure just how those bar graphs show usage on multi-rate tariffs.
I’m guessing here, but is there perhaps a seperate set of charts that show the midnight to 7am off-peak usage?

plan

Ok. Here is more info. I had to change the account holder from Mum to myself, as Mum is not able to manage payment of the bill. 
 

I tried to do this online, but quite sure I mucked it up. 
I somehow cancelled Mums account, but then got it moved to myself. This is why the views prior to April 2025 are showing as blank. 
 

When I was next Mum we spoke to Ovo and got

the all clear for me to be paying Mums account.

I still cannot understand the usage. And especially when looking at the following images which are views from my Mums account before April 2025. 
 

I did find that Mum has had very high usage in the past. This is for colder Months. 
 

You should also have access to all of your mother’s past bills with OVO. Was she with another company before April 2025? What kind of meter did she have before the smart meter was installed? Has her property ever had a heating system such as storage heaters? Did it once, perhaps, have Economy 7 to control heating and hot water? Did she once have an RTS (Radio Teleswitch) meter that was removed when the smart meter was installed? Like many here, I am really trying to work out why, as you have noticed, there is no recorded usage on your graph display from midnight to 7am. This is, as I am sure you have also noticed is 7 hours. The clocks changed on March 29th this year. Could you look at a day in March before that date? Is it still midnight to 7am that shows no usage?

​@Bendog lots of questions I can’t answer I’m afraid. 
but I think you’re on the right track. Spike started shifted the 1 hour after March 29

Here is the 29th. Interestingly no

major spike in the morning.

The big thing that stand our to me there is one word in those screenshots “Estimated”.

If previous billing has been based on estimates and not actual readings - (and if the new smart meter not providing readings to DDC yet? As apappears to be the case) - then it may be that the latest usage figures are also estimated.

Similar to as ​@Firedog asked above please check the recent meter reading history, since the new smart meter was installed, does it say “Smart” or does it say “Estimated” next to them?