How is data recorded on the online graphs and tables?

Mmmm, If the red is the missing data then that’s oddly consistent. It looks too consistent to be coincidental.

Putting it into 24 hour notation those red periods are 23.00 one day and the following half hour,  00.00 the next day.

PS. I’m discounting the readings after the 25th because the change from BST-UTC always screws things up for a while.

It almost looks like something switching on at around midnight and generating a signal/field strong enough to swamp the meters Zigbee signal for a while?
(Your seemingly large 24 min or so meter-data to clock time discrepency may mean it’s happening at exactly midnight?)

Would something switching on around midnight like that make any sense to you?

(Could the glass kiln even be the culprit? It may seem an odd time but I know nothing about how glass may be tempered or annealed so perhaps a midnight heat cycle may be called for).

Our gas usage via Hive is as follows: Heating (set at various temperatures, dependent on room/area) is on from 6.30am until 11pm each day. We now put the water on when we are about to use it. We discovered that, although the tank appears to be well-lagged, when we had it set to heat up for 30 minutes each day, on days when we were not actually here to use it the cost for doing this was the same as if we had used it. A 30 minute boost allows us to both have a shower with enough left to wash stuff that cannot go in the dishwasher.

On the days when no data was recorded on the Day tab, the Month tab shows that we used 0 kWh of gas. (We were not here to use it). It seems that the system cannot cope with zero usage.

I have not used my electric kiln in the last month. After around 10pm each evening, the only things using power are the tropical fish tank (just filter pump and thermostatically controlled heater, no lights), fridge freezer, my PC and monitor,  one light in the dining room and one in the hallway (both LED). In addition, there may be a phone or my Kindle on charge. At midnight, our electricity usage is around 0.15 kWh on average. 

I intend to start today recording the half hourly data as reported by the Day tab for gas in the same way as I have been doing for electricity. That may give me some clues. Our gas meter is actually in the ground at the front of the house while the electricity meter is on the side of the house. A couple of times in the past, it does not send readings (this has not happened for a while) but they resume if we, physically, wake it up! In order for the meter fitter to install the gas meter, he had to completely reconfigure the piping. He was here for about 4 hours!!

Afternoon ​@Bendog and sorry this has taken a while.

I’ve had it confirmed that, for example, the half-hourly usage interval labelled 6:30am is the 6:30-7:00 interval.

Hope this helps!

So, when my boiler fires up at 6.30am, any gas usage should be recorded in the 6.30-7.00 interval. This is not what is happening. Our gas is controlled by Hive and is set for heating, when the thermostat or individual room TRVs require it, between 6.30am and 11pm each day. This is an image of an extract of the data recorded on 18th November. 

As you can see, there is usage shown for the 6-6.30am slot. The same thing happened on 16th November.

Slots with no recorded data, not even 0 kWh continue to occur in the same two slots on a random basis.

 The most recent of these were the 10.30 and 11.00 pm slots on November 18th. The previous date this happened was November 15th. As a result of this, it would be impossible for us to choose a 9pm-11pm slot for the new “help with heating initiative” as we could never be certain when the usage was a) going to be recorded at all or b) going to be recorded in the correct slot. This is not what smart meters are advertised as being able to do. They are “sold” to us as making things easier, not as something that customers are expected to have a maths degree to understand (tick) or be willing to gamble on whether, on a particular day, accurate data will actually be recorded. Don’t get me wrong, I would still rather have a smart meter than the old meters it replaced. At the ages of 70 and nearly 74, not having to kneel down on frozen ground to read the old meter each month is wonderful. While the missing slots should not impact the actual cost of our usage, it would be nice to be able to see exactly when our gas usage happens and try to tie this up with what we might be doing at that time. 

That answer given yesterday by Ben was the answer to your original question in you opening post of this thread:

As you can see, two values are recorded: 8.30pm and 9pm. If usage is recorded at 8.30pm, does this show what has been used between 8pm and 8.30pm or what has been used between 8.30pm and 9pm?

Whilst it is correct as far as it goes, it is not the full story - particularly when it comes to gas metering.

Our discussion has moved on and we have got into discussing the difference in alignment between the meters 30-minute periods and the clock half hour.

Of course you don’t see that on electricty meter the report usage to the coms hub within seconds, only with gas meters that report in 30-minute packages.
30-minute packages that are not exactly aligned with the clock half hour.

​@Bendog did you do any testing yet to pin down just how many minutes your gas meter offset is?

It is about 15 minutes, we think. However, now we have a change in the weather, we may have to wait until we are only using the boiler for water to narrow it down further. It is just really frustrating that OVO have decided to expect us to be able to work out something that will be individual to individual meters, it seems unfair that the offer is available, with a guaranteed reward, for electricity only customers who just need to pick a slot. In the first slot I booked, we managed 5.95kWh for the first hour but only 2,6 kWh for the second because of the time offset. In the second one we managed to use over 5 kWh in each because we did a 15 minute adjustment to the slot start time. The first slot should credit us with the cost of 7.6 kWh while the second should credit us for the full 10 kWh. However, we do know that we should not chance picking any 9-11pm slots given that 10.30 and 11pm are the slots that are so often not recorded at all.

​@Bendog we are discussing, and actively testing, this issue ‘backstage’ I for one am coming round to thinking that there is a solution to this apparent time offset with gas meters - it’s just not a solution that is automatically used.

It appears that when a gas meter is more than 10 seconds out of sync with ‘clock time’ it will not try to correct itself but will send “alerts” that attention is needed.
However as the ‘glitch’ makes no difference at all to your gas billing then it it is not a priority to look at.
(Or in other words it gets ignored as being unimportant - which is fair enough because it makes no, well very little, difference to billing).

However there is apparently a command “Set Clock” that can be sent by support to gas meters, to re-sync the meter with clock time.
You might want to ask support to try it for you - (I want do do some more testing recording before I ask them).

I have already been in contact with them regarding both the offset and the irregular missing data slots. As you have said, since the overall usage is correct via the daily meter readings that are used to calculate this, they do not view it as a problem. In the great scheme of things and, under normal usage, of course, it is not. I have been aware since our gas meter was installed that the start time actually recorded and the start time of the actual boiler has always been “one slot out” - i.e. it records usage in the 6am slot when the boiler actually comes on at 6.30am. It is only now, with their attempt to use the exact same method as the free electricity initiative and apply it to our gas usage that it does become a problem.  To be honest the simplest solution for something that they do not really want to support to make correct would be to allow us to choose just a day and the 10 kWh rebate be applied to that day. This is, in reality what they have done for electricity-only customers. We are paying a daily standing charge for our meters and we should be able to expect that they are totally accurate both for time and usage. I have, incidentally, contacted them regularly, in the past regarding their apparent inability to deal with the switches between GMT and BST - after all, these have been standardised for years - they do not come as a surprise!!

i can only agree with your comments there.

TBH though gas is a fossil fuel and so doesn’t fit in with the OVO ‘Plan Zero’ ethos.

You can sort of see why they obviously regard gas as second class; and would probably not have anything to do with it if they could get away with dropping it and selling electricity only.
But of course that would risk losing customers who prefer to have one supplier for both fuels.

PS, Here’s an off the wall thought about fossil fuels.
Gas, Coal, and Oil, are in fact renewable fuels. It just takes a very, very, long time for them to renew. (much longer than it takes to burn them).

I feel a bit of an intruder in this thread because, gas not having been invented in this part of the world yet, I’ve no personal experience of gas meters to go by. However, here are a couple of general remarks:

• I honestly can’t tell from the red figures in ​@Bendog‘s table whether he’s missing all the data for some days or just between noon and midnight. I just don’t seem able to say at a glance whether 12:00 AM/PM refers to noon or midnight - to this old dog, 12:00 will always be noon - the Meridian to which the ‘M’ in AM and PM refers.
• We don’t have to depend solely on our supplier to retrieve usage data from our meters. Anyone with the appropriate permissions can retrieve them given the data owner’s authority. Bendog might see how he gets on with a utility like Bright, which should be able to request both electricity and gas usage data from a SMETS2 meter.
  [NB Bright et sim. can only retrieve usage and tariff data. They’re not allowed to retrieve meter register readings.]   
• The question of which half-hour a particular usage data item belongs to is a bit vexed, as I think I pointed out earlier. This graphic shows how different datasets are presented:
    

  

• I’m sceptical about ​@Nukecad‘s theory about the gas meter clock being stuck at ‘time of installation’. It must be part of the commissioning process to synchronize the meter’s internal clock with that in the CH; what happens subsequently is anybody’s guess. 
• I’m not quite sure what Bendog is referring to here: “I have, incidentally, contacted them regularly, in the past regarding their apparent inability to deal with the switches between GMT and BST.“ OVO’s account pages have for some years struggled to present usage data in an orderly and accurate fashion during summertime, but they got it right in the summer just past. Where are you now seeing BST not being treated properly?