My usage as shown on the OVO website has been changed retrospectively - huh?!

Yes @timfg , it’s the meter readings themselves which are key in charges. One of the regular posters has pointed out that on one of the cost pages you can see some figures underlined (usually actual readings) and others not (often estimated readings). 
Even then gas figures are calculated from other data from national grid, not published until after the event and so even with actual readings, these sometimes need a correction. 
Dec 31st was a problem date for many readings. With price changes the data storage centre was busy updating and lots of meter readings got delayed. Eventually corrected of course

Yep, a similar thing happens on every what was 6 month change and is now 3 month change on my account for example. I see something every time on my readings page

@timfg i am not sure if your actual bills have changed, but perhaps vote for this if you think it might be useful?

Interesting.  I have smart meters, updating every half an hour, which I assumed meant that these readings (and costs) were accurate - but, reading other similar concerns, it appears that’s far from the case.  I’m struggling to understand why that would be so: if my meter is recording my usage every half an hour, what better measure can there be of the energy I have used? The price I am charged for that energy is a known, even at the point of a price cap change, with an adjustment seeming appropriate if there is a delay in receiving a reading on that day, but should have minor effect.

I am not particularly concerned about the accuracy of what I am being billed, but publishing data at this level of granularity seems pointless when it is, in fact, subject to adjustment and significant correction. I did see a big blip at the March price cap change, which I have never questioned, but it now seems it’s probably a result of the same thing.  It appears the figures published for daily use are just a fairly blurry estimate of reality and the best they will ever be is a broad retrofit of the numbers, distributed according to some unpublished algorithm as a best guess that matches actual (and billed) usage.  It makes a mockery of all these shiny dashboards and datasets, which imply some degree of precision and transparency that simply isn’t there.  I would very much like a clear indication of the point when the data is as good as it is going to get (ie no further massaging to be done) so I could at least not waste time on it any further.

And, for the record, this is what my data capture for the last 18 months looks like.  Clearly, the March price cap change needs revisiting…

Personally I’d much prefer that Ovo made the raw data available for any selected period, published only when they could commit to its finality, rather than have to scrape it off the website month by month - a laborious process at best - only to find that the data isn’t even accurate.  The whole approach is something of a transparency sham and needs some rethinking.

The smart meters certainly capture the data @timfg but it’s often the communication back to the data hub which is not always made in the same timescale. When the readings do get through then what might have been an estimate on the suppliers system gets updated and therefore changed. 
There are a number of third party apps which can also track this and graph for you. 
 

Incidentally, the data for the national grid gas calorific value is also available 

Interesting.  I have smart meters, updating every half an hour, which I assumed meant that these readings (and costs) were accurate - but, reading other similar concerns, it appears that’s far from the case.  I’m struggling to understand why that would be so: if my meter is recording my usage every half an hour, what better measure can there be of the energy I have used? The price I am charged for that energy is a known, even at the point of a price cap change, with an adjustment seeming appropriate if there is a delay in receiving a reading on that day, but should have minor effect.

I am not particularly concerned about the accuracy of what I am being billed, but publishing data at this level of granularity seems pointless when it is, in fact, subject to adjustment and significant correction. I did see a big blip at the March price cap change, which I have never questioned, but it now seems it’s probably a result of the same thing.  It appears the figures published for daily use are just a fairly blurry estimate of reality and the best they will ever be is a broad retrofit of the numbers, distributed according to some unpublished algorithm as a best guess that matches actual (and billed) usage.  It makes a mockery of all these shiny dashboards and datasets, which imply some degree of precision and transparency that simply isn’t there.  I would very much like a clear indication of the point when the data is as good as it is going to get (ie no further massaging to be done) so I could at least not waste time on it any further.

And, for the record, this is what my data capture for the last 18 months looks like.  Clearly, the March price cap change needs revisiting…

Personally I’d much prefer that Ovo made the raw data available for any selected period, published only when they could commit to its finality, rather than have to scrape it off the website month by month - a laborious process at best - only to find that the data isn’t even accurate.  The whole approach is something of a transparency sham and needs some rethinking.

You may already know this. 

The 30min data is never added up to make a daily total on your bill.

The meter will transmit the information separately. 

This is what feeds your bill assuming you are on a regular tariff

https://account.ovoenergy.com/meter-readings/history/electricity

https://account.ovoenergy.com/meter-readings/history/gas

Ideally there will be a reading every day and they all say smart

Don't rely on anything on the usage page for billing purposes. 

Sometimes there can be issues pulling the data off a smart meter and you end up with some estimated readings that are then sometimes updated. It could be an issue with a local transmission aerial in your area for example or heavy network traffic at every price cap change.

… and, interestingly, the April price cap figures are unchanged.  So that spike at that point seems very odd and unlikely to be a good representation of my actual usage over those few days.

I also found the page that shows whether readings are estimated or accurate: mine are all ‘Smart’ right up to today at the moment - which suggests that none of this data-massaging has been driven by non-receipt of readings, but by some inadequacy of central process.  I really don’t get  why such big changes would be needed: my usage is accurate to the half-hour, the price I pay is known, the standing charge is known

Interesting.  I have smart meters, updating every half an hour, which I assumed meant that these readings (and costs) were accurate - but, reading other similar concerns, it appears that’s far from the case.  I’m struggling to understand why that would be so: if my meter is recording my usage every half an hour, what better measure can there be of the energy I have used? The price I am charged for that energy is a known, even at the point of a price cap change, with an adjustment seeming appropriate if there is a delay in receiving a reading on that day, but should have minor effect.

I am not particularly concerned about the accuracy of what I am being billed, but publishing data at this level of granularity seems pointless when it is, in fact, subject to adjustment and significant correction. I did see a big blip at the March price cap change, which I have never questioned, but it now seems it’s probably a result of the same thing.  It appears the figures published for daily use are just a fairly blurry estimate of reality and the best they will ever be is a broad retrofit of the numbers, distributed according to some unpublished algorithm as a best guess that matches actual (and billed) usage.  It makes a mockery of all these shiny dashboards and datasets, which imply some degree of precision and transparency that simply isn’t there.  I would very much like a clear indication of the point when the data is as good as it is going to get (ie no further massaging to be done) so I could at least not waste time on it any further.

And, for the record, this is what my data capture for the last 18 months looks like.  Clearly, the March price cap change needs revisiting…

Personally I’d much prefer that Ovo made the raw data available for any selected period, published only when they could commit to its finality, rather than have to scrape it off the website month by month - a laborious process at best - only to find that the data isn’t even accurate.  The whole approach is something of a transparency sham and needs some rethinking.

You may already know this. 

The 30min data is never added up to make a daily total on your bill.

The meter will transmit the information separately. 

This is what feeds your bill assuming you are on a regular tariff

I didn’t, actually. I would have guessed that the 30m data isn’t ‘added up’ to make up the bill and that it was based on a known reading at the billing point.  But I would also expect the daily usage figures, assuming that readings are being transmitted, to near-enough exactly align with the ultimate billing for someone like me on a tariff that is known.  The fact that such huge adjustments might be needed says to me that there is something very wrong with the timeliness and precision of what happens centrally in the publication of the data. Which, frankly, shouldn’t be published.

Up to you @timfg 

You can follow up with the OVO Support Team

https://help.ovoenergy.com/#contact_us_container

It is just customers sharing our knowledge on the forum.

Alternatively post an idea in idea section

https://forum.ovoenergy.com/ideas

We added one idea as a starter that you can expand on

But obviously feel free to add nee ideas you think are needed or would be useful. 

Feel free to post any further questions and i am sure one of the regular customers here will try and help. 

I’m not sure there’s much more help to be garnered! It’s been useful to update my understanding of the reliability of this data and I’m disappointed to find the precision of what’s published to be rather less than I feel should be possible.  But I think it’s probably an ‘is what it is’ thing.  If anything, it’s confirmed my historically-held suspicion that smart-meters are not the data-scientists’ wet dream that some hold them up to be 😁

Thanks for your input @Jeffus