How is data recorded on the online graphs and tables?

Only someone with a smart gas meter can tell you that, and I’m not. ​@Nukecad is, so I’m sure he’ll be along shortly.

I can say that for electricity, the meter operates on a bucket principle: it starts filling up, and then 30 minutes later it’s weighed. The weight (in fact the quantity of kWh used in that period) is stored along with the current time stamp, and a new bucket starts filling up. So an entry in the datastore labelled 20:30 indicates the amount recorded from 20:00 to 20:30. OVO then choose to manipulate these figures, labelling and reporting that same entry’s quantity with a time stamp 30 minutes earlier than that recorded.

​@Nukecad will be able to confirm or refute whether a quantity of gas displayed with a time stamp of 20:30 passed through the gas meter in the period 20:00-20:30 or 20:30-21:00. You could also do your own experiments to find out, by taking meter readings at the beginning and end of a 30-minute period and consuming a ~known large volume of gas during that period. 

The reason that I am asking is to try to work out when I should heat up my hot water tank in order to take advantage ot the 9pm to 11pm slot I have booked for next week for the “winter free heating help initiative”. Last night, we set the gas to heat up the boiler from 9pm to 10pm and these are the values that were recorded. So which values will OVO use to record my usage during the time slot? I am SO confused!!

The time is the Start of the half hour period.

For example my gas boiler timer is set to be off all night and fire up at 7 in the morning so I see this as it starts burning gas at 7:00am:
 

Ah, i see.

It is free gas during the two hours that you have booked (up to 5kWh free in each of the 2-hours) - So to take advantage you have to use the gas during those hours.

Which in your case would be to heat the water tank on that day between the 9pm to 11pm that you have booked.

Using gas at any other time than the 2-hours that you have booked will be charged as normal.

Last night that is exactly what I did to test out what would happen. I set the water to heat from 9pm to 10pm, but the daily data table records it as having been done between 8.30pm and 9.30pm.  No usage was recorded for any time outside of those two periods. That is the basis for my confusion. Nothing else was using gas at the same time as the heating was switched off in order to make this a “fair test”.

Where do you select these times (I know nothing about gas boilers)? Are you sure that the timing device you’re using has migrated from BST to UTC? [It wasn’t until this evening that the MSF radio-controlled clock in my kitchen finally decided to relinquish  summertime until next Spring.]

If that’s all in order, it might be worth doing a couple more similar experiments, varying the start time by 10 or 15 minutes either way. I know it’s tedious having to wait so long for the results, but you may learn something valuable by doing it. 

THIS HAS BEEN EDITED TO HALF-HOURLY DATA PACKAGES - so some sections quoted in later posts no longer match.

 I do know the cause of that one - because I saw the same thing when I first looked at mine.

I looked into it and decided that it’s to do with the gas meter only sending packages of data at 30 minute intervals.

However that 30 minutes of data doesn’t line up exactly with ‘clock time’.
I believe that it depends on exactly what time the meter was commissioned/ connected to the HAN.

Depending on just what time that was you could get up to 29 minutes of gas usage showing in the previous ½ hour clock period.

So for example if you meter was commissioned/connected at a time such as 13:19 the first packet of data would be sent at 13:49.
The next packet of data will be sent at 14.19, however becauses it started at 13:49 will be shown in the 13:30-14:00 time slot, - even though most of it was actually used after 14:00

When I had my gas heating set to come on at exactly 7:00 i would get a small ‘mysterious’ usage recorded in the 6:30 period. That’s when I went looking for the answer.
 

Changing the boiler start times (mine is a manual timer, but although the on-off is at 15 min intervals I could still set the time in 1 minute intervals) and watching what happened with the ‘6.30’ usage I found a discrepancy of around 6 minutes in ‘boiler time’ to ‘meter data time’.

So let's say that my meter was commissioned at 6 minutes past the half hour.
That would give a 6 minute discrepancy between the meter 1/2 hour data periods and the clock half hour.

Meaning a data period starting at 06:36 would run until 07:06 but would all be reported as being in the 06:30 to O7:00 timeslot.

So when my boiler fired up at 07:00 the first 6 minutes of gas usage were reported as being in the 06:30 to 07:00 timeslot.

(Then when I changed it so that the boiler fired up at 07:15 nothing was reported in the 06:30 to 07:00 timeslot).

As the gas tariff is the same then it isn’t usually a problem exactly when the gas was used.
However with something like the Free Gas offer it becomes a smal thing to factor in.

One thing I would add is that 4.94 kWh for up to 10 minutes of gas usage seems a lot, but I suppose that depends on your meter data to actual clock time offset.

Your explanation makes sense as we have noticed our heating being shown as on in the 6am slot when it is actually set to come on at 6.30am. The boiler is in our garage, so we often cannot hear it in the house.

How can I find out if the meter is set to only send every half hour? I am not sure if the picture of the meter helps.

​@Nukecad Thanks for chipping in 🙂
    

I rather though that routine data transmission was at 30 minute intervals, to prolong battery life. Where did you learn that it’s in fact at 10 minute intervals?

SMETS2 says:

Good question which I don’t have an answer for, so I don’t know why I said 10 minutes.

(However I still have a niggling idea I’ve seen something about the gas meter recording data internally at 10 min intervals but only transmitting that data to the comms hub every 30 mins. Maybe it was an article on ToU tariffs and data granularity??)

I don’t think it changes my (unproven) theory about the meter commisioning time though, it would just mean larger possible offsets/discrepancies, such as that 4.49 kWh.

eg if the meters data ½ hour started at 08:58 then the gas used between 08:58 and 09:28 all get reported as being used in the 08:30-09:00 timeslot on the chart?
I believe that it does work like that.

Lets face it unless the meter fitters are going to stand around waiting to commision meters exactly on the clock half-hour then there will always be variation.
So it’s then a question of allocating the meters half-hour data, to a clock half-hour shown on the charts.

Like I say above normally it’s just technical detail that would make no difference to billing, but for something like the 2-hours Free Gas then it becomes more important to know just what your own gas meter varience/uffset is.

I’ll have to think about it a bit more, but as I’m currently running a fever of over 38 C I’ve not been on top form for a couple of days. (Flu, I had the jab last month so it must be a new strain since they formulated the vaccine).

Edit.
I have thought it through and edited my post above,
However it does not make any difference to my theory about gas meter data offsets to actual clocK time.
It looks as if the Beyond team responsible for the free gas offer may not have considered it either.