There are differences in timing due to the smart meter set up which as far as I’m aware do not change when the clocks do. There’s an idea thread on the subject here 

If Hugo also has the timing ‘out’ then it’s likely due to that although half an hour rather than an hour is odd. 
As long as your start and end readings are accurate, non of this should make any difference to your bill which is not driven from the half hour data

That’s a possibility but why can’t OVO answer the question !

Hi @Simon.p 

I get data from the OVO app, n3ergy and Glowmarkt and, you guessed it, they are different!

At this time of year there is no difference between GMT and UTC so the odd hour shouldn’t be an issue.

My Data for 1st Feb:

Interestingly neither are actually “correct” time wise. Our heating turns on at 06:30 so the 06:00 time slot should show zero.

Our heating turns off at 22:00 so there shouldn’t be any usage in the 22:00 time slot.

I actually combine all three lots of data together into one database, and, so that I can reconcile the numbers I add 15 minutes to the OVO and Glowmarkt data and subtract 15 minutes from the n3ergy data..

This makes more sense regarding the 06:00/06:30 data since for the first 15 minutes or so the boiler is at high fire, heating up the house, and then it modulates down.

In the summer our hot water turns on at 16:15. The above tweaks to the time then agree with actual usage.

Good luck!

Thank you for your reply, I have a full smart system with weather compensation, it’s a 30kw boiler range rated to 11kw, so the start demand is low with w/c activated,whatever I try it’s always half an hour earlier.

The difference between the OVO and Glowmarkt numbers looks like a simple question of calorific value. OVO will be using the appropriate daily figures, but I think Glowmarkt use a constant CV -  40, by the look of it (4.32 x 1.02264 x 40 / 3.6 = 49.087). 

I noticed that my own n3rgy data apparently allocate the midnight slot (timed at 00:00) to the preceding day, so a day’s data start with the slot timed at 00:30. This would explain the half-hour’s displacement in your n3rgy column. I only have electricity data, but I don’t imagine there’s any difference with the gas numbers.  

To illustrate the n3rgy phenomenon:
  

I wonder if some similar sort of shift is happening to Simon’s figures.

Hi @Firedog and @Simon.p 

I agree re, CV data, however it might be that, since I download Glowmarkt data weekly, and OVO data daily, that the Glowmarkt CV data has been updated with the “corrected” CV data, whilst the OVO data hasn’t (it can take a day to produce the final CV data).

Coincidentally just walked past the IHD at 07:14 reading was 0.79 kWh, then at 07:18 reading was 1.81 kWh (and at 07:35 still 1.81 kWh).

I believe the gas meter is battery powered and to reduce battery drain it is read periodically, probably every 30 minutes.

Yes only every 30 mins and often not ‘available’ until several minutes after the half hour. 

Thank you for your reply, the gas meters do report half hourly, but should start on the hour of consumption not before, with weather compensation the boiler is constantly topping up over a 16 hour period, so the IHD will show a constant average over that period. Normally between 6/11 pence per hour, been on since 6am