What sort of meter is/was that @chipp1a (previously)? If it’s a smart meter then there may be a record of timed use. Otherwise I’m not sure how you show how much was used when. 
There may be a way to show typical use over a period but not sure how that might be explored

Have a look at the meter readings page. I have an E7 smart meter and this is what I see:
  
 

The readings for the two registers are clearly marked, and they also appear on the billing page as an expander under Charges in detail. Of course, this degree of granularity depends on the frequency of submission - my readings are sent every half hour.  

If you see readings for two registers, the chances are that the correct rates have been applied. You’d see this in the billing history. If the readings for one of the registers are missing, it gets more complicated, but it may still be possible to reconstruct the usage pattern for the previous year. Did the engineer who installed the new meter leave a sticker on it showing what readings he was able to retrieve from the old one?

Hi, thanks for the replies. So the original engineer that attended advised that the cable to the off peak box was no connected and the box was sealed off. Two further engineers then attended and installed a new smart meter. I am unsure of the exact make or model of the smart meter. 

I have checked his energy bills and from 11th December to 10th January it has his daytime usage recorded as 441kWh (£189.94) and his night usage as 26.6kWh (£3.84). 

Considering this is a small one bedroom flat the usage recorded seems quite high? I don’t know if you would agree? 

Any more thoughts before I get in touch with them?

Have a look at this page on the website not the app

https://account.ovoenergy.com/plan

You should see Future Annual Consumption.

This is how much your father in law typically uses in a year, automatically updated as the smart meter sends readings

What does it say?

Ofgem publish typical domestic consumption values. For E7

Low 2400 kWh

Medium 4200 kWh

High 7100 kWh

For the period you mention he used 467.6 so 15kWh a day. Obviously depends on insulation, heating, cooking etc. but not unreasonable. He could easily use 1 kWh for heating an hour for example in winter in some properties. His winter usage will be dramatically different to summer.

I assume he doesn't have gas at all. 

Given the peak, off peak split it does look like he would probably be better off on a normal tariff? He doesn't look like a typical E7 user

Thanks for the response, it says 2786.8 kWh.

No he doesn’t have gas at all.

So what would you say was the issue with the E7 meter with the off peak cable not being in the meter? If it has still been reading the night time usage then it couldn’t have had an effect on it could it?

Doesn't look like an unreasonable consumption then. 

I will be honest i am not sure about what impact the cable has. 

As an aside how does your father in law use E7. Does he have night storage heaters that are setup to charge overnight? 

I’m sure @Blastoise186 will correct me if I’m wrong, but I think the meter is smart enough to stop counting on the daytime register when the off-peak period starts and vice versa. So any night-time usage will be recorded and charged at the cheap rate. The less-than-1kWh-a night would tally with what the fridge, freezer and any other ‘always on’ stuff would consume.

The missing connection sounds like the feed to equipment designed to operate on cheap-rate electricity, e.g. storage heaters and the immersion heater for hot water. Since FIL has only used 27kWh at night during a whole month, it’s fairly clear that none of this sort of equipment is working as intended, if it’s present. This is quite likely if there’s no feed to them; the feed passes separately through the meter to ensure that the power-hungry appliances only operate when electricity’s cheap(er). I wonder how he’s been keeping warm - if he’s using electric fires or something during the day, and perhaps switching the immersion heater on, this would explain the unusually large 440kWh daytime consumption. 

The costs you showed work out at about 43p/kWh by day, but only 14p/kWh by night. Even if these figures exclude VAT, that night-time rate looks quite favourable in the current climate - mine is 23p. Let’s hope that if he does have storage heaters and an immersion heater, that the new meter installation starts delivering power to them overnight (it’s difficult to understand why there’s an E7 meter unless equipment is also in place to take advantage of it). This could easily shift 10-12kWh from day to night; 10 x (0.43-0.14) x 30 =  £80+ per month saving.

I can vouch for this. :)