Givenergy data accuracy

What with the current times and us all being more sensitive to usage etc, i have just received an unexpecredly large electrcity bill, so have been comparing my usage as recorded on my meter v the givenergy data.

Now, i certainly dont expect them to allign, and there is of course a margin of error, but there is quite a large gap:-

My meter reading says that i imported 340kwh over the 30 day billing period, while the givenergy inverter data reports an import figure of just 263kwh!! So givenergy seems to be under reporting by about 80kwh or roughly 30% ?

There must be an issue here, what level of accuracy are others seeing ?

Thanks,
Eamon

30% seems like a high difference. I posted a similar question a while back https://community.givenergy.cloud/d/438-how-accurate-are-the-import-from-grid-metrics . For the most part I'm not seeing a huge difference between what GE says compared to what my energy provider says. I've since been changed to a Gen2 inverter (Gen1 died on me) and it seems to be a bit more accurate too.
If I was you, I'd manually monitor your electricity meter to make sure your provider isn't over charging. Assuming you're on a "smart" meter and your provider isn't estimating or waiting for a meter reading?

feidhlim

Thanks, im not on a smart meter, i have the old type spinning meters, and the readings for the period and duration were read and not estimated.

I dont see anyway of verifying the electrcitiy meters accuracy, and to be honest think its unlikely to be that at fault, given they are in theory highly accurate calibrated devices.

No offence to giveenergy, but would think the most likely first port of call would be thengivenergy data and check the accuracy of that (as much as i would like the actual fault to be with the electricity meter)

Eamonnogorman

You can check the live power accuracy
On the meter is a number rev/min/kw
put something high powered on, such as a kettle. Then count the number of revolutions' in a Min to work out the power. Compare that to the reading on the GE inverter.

You can also look at kwh comparison.
Using Reports, set a start and end date to match your billing cycle of your latest bill.
Compare the grid usage and your bill

Thanks, will run the report shortly, will have to do the "kettle test" when no solar production

Isn't the EM115 meter supposed to be accurate? I believe you can scroll through the values which are stored in there - you may be able to compare these both before and after the kettle test.

I think it's the GE reports that do this but I recall making a comment on FB to someone else who noticed this and one of the GE Devs gave it a thumbs up (which I assume meant it was somewhat right?)

The reports sections add up the 5min data intervals for things like load power, PV Power etc & then take that as a given it did the same across the whole 5 min period - rather than using the true inverter derived cumulative totals for each the time period instead? Something along those lines anyway.
Don't take that as anything gospel I've never really sat down and checked!

Also you have a spinning meter, so to complicate things for you it will go backwards on export and decrease your import values (which in theory gives you net metering) however as you have had a larger bill this would only explain if your bill was lower than you expected.

hoggy

Thanks,

With regards the spinning meter, sadly it only spins forwards, the ones thay spin backwards are like golden hens teeth now :-)

On the 5 min data sampling, I get the concept and the potential for deviation lookong at that, but with the app reporting at 10 sec intervals, i would have thought that the end ofnday aggregate data would maybe be more accurate!

30% is a big variation, it can be difficult to manage or improve your consumption with that level of delta ?

Eamonnogorman my inverter consumption vs billed consumption is out by 60% at the moment - albeit small numbers per month. Will see how it works when I pull more from the grid over winter, but I wouldn't rely on the portal figures for anything other curiosity

Cdent @Eamonnogorman I agree wholeheartedly with @Cdent; read the same meter your supplier uses to charge you for estimating how much your bill is going to be. The EM115 displays the import to date on the portal, so you can make a note of that reading each day, or go back through the data tables to get it. I mention this because if the inverter loses connection to the cloud, the five-minute values are lost. However, my portal reports 275kWh import (EM115 meter value) since installation, compared to 340kWh for the same period on the smart meter.

I think the Givenergy portal is lots of fun and good for comparing one period with another but working out a budget? No, I'll use the same data as my energy supplier for that.

I have exactly the same issue, panels and batteries commissioned Aug 1st, software says I used 275kwh from grid, meter says 391kwh
I had lots of problems in 1st month with firmware so battery was offline most of month.. I think the first option is to keep a check on it and I'll be watching closely to see if gap narrows... hopefully it does

Same problem with accuracy here. Grid meter a good 30% higher than GE.
Have been researching and found some modern electrical equipment causes um, pulses may be the easy term. These can be misread by the grid meter, even Smart ones. This has been known about for some years and you can look it up. There are research papers on the subject and useful comments on the Octopus Energy website. Why not read about it? It's really worth while reading it! Look under The Perils of being a tech innovator, on Octopus agile.
Most meters affected may run backwards, but no, not mine!
This fluctuation comes from switching, which is used in variable speed motors, dimmer switches and your inverters. Most stuff is supposed to have chokes to prevent this, but maybe they are not that good. I read that flourecent and LED lighting can also do this.

Umm. Sorry Tim, but you say the GE portal is a "lot of fun"?
You've spent what? £5000 on a toy? Should have stuck with Darth Vader.

I see the system as a way to reduce my draw on the grid and do a bit for the Planet, as they say.
However, inaccurate reading and recording puts into question the quality of the other values provided in the display. The algorithms can only provide accurate output if the inputs good. So what use is there in being told you've saved 4kg CO2, where you may actually have only saved a fraction of that?

Sorry if this sounds a bit heavy, but this but of kit is a tool and should be highly reliable. You would not accept it if your computer refused to give you the right answers, surely.

I want a high tech piece of equipment to do what it says on the box.

OK, I'm going back k to sleep now.

Have fun.

MikeReynolds We spent far more than £5k on our installation but we didn't buy it as a toy. We bought it to reduce our energy bills which it does very well. What it doesn't do well is register house load or display data that can be relied upon to make financial decisions. The primary purpose of the EM115 is to minimise grid import and export in ECO mode. It does that extremely well, but as for the pretty pictures in the portal; they're just wrong. The solar production in the reports for last year doesn't include both inverters. House load on the portal is only one inverter.

I could be ar**y about the fact that the portal is wrong but I realise that Givenergy have plenty of other real issues to sort out, not least being the sudden SoC drop and the much-vaunted new products. We are content to let the system do its thing, knowing that it's saving us money and reducing carbon emissions. ultimately, when they get round to fixing the bugs in their portal for our configuration, we will also be able to see values closer to reality. But even then, they will be different from those recorded in the smart meter and trying to work out which is "right" is wattless effort.

OK people
Anyone started to read up on how far widespread our problem is? Phile Steele of Octopus thinks it only affects a few, however across the 3 threads I've seen on this forum, there are over a dozen who have taken the time to comment.
It is very likely that there are many more who have not, or are unaware of the difficulty.

The Octopus article looks at a Tesla battery with L&G meter and Phil Steele thinks the problem is quite restricted as they have only found 2 meters misreading. However, as we are seeing that same reaction, then the problem is probably much wider than he forecasts.
Let's try to do something about it, eh?

I would suggest we begin by listing our various systems with the type and model of Import meter.
If you like, I will collate the results.

My system has 4kWh PV panels (2012) with 8.2kW GivEnergy hybrid battery (2021) and Import meter is a Smart Aclara SGM1411B with a Toshiba sender (2022) .

Phil Steele does ot think this is a big problem, but the Government have been tightening up legislation since 2006, specifically because meters are recording inaccurately. This has lead to the MID performance that our meters are supposed to on form to.
Lookup Association of Meter Operators, they have a very long list of meters that are suspect.

Don't feel shy here. GivEnergy may want you to press lightly (as they are developing new products), however these new products will be no better than ours unless they get the the systems are designed as a whole, rather than piecemeal.

I am not sure if this helps in this situation, as I have a smart meter and not an old mechanical meter, but as a sanity check on my new smart meter I used a true RMS AC clamp meter (Uni-T UT210E). This allowed me to measure the current being pulled in from the grid (during battery charging), which I was able to compare against the current registered by the smart meter. Of course, this does not prove that the meter is correctly calculating the power, and then correctly summing this over time - but it is better than nothing.

Just thought I would throw that in...

(As a side note: This particular meter is quite nice in that it can also measure DC current using the clamp, up to 100A. Good for measuring current between the battery and the inverter. It does this using a built in 'hall sensor', although it does need zeroing each time you use it.)

MikeReynolds Octopus article looks at a Tesla battery with L&G meter and Phil Steele thinks the problem is quite restricted

If you want to signpost other posts on this forum or external web pages, it does help tremendously if you embedded the URL into your post, or if you can't do that, then just paste the link in at the end. I did spend the time Googling the Association of Meter Operators but the only lists I can find of relate to reverse running meters. Reverse running is an issue if you have a microgeneration system but otherwise not. The accuracy of the metering is an issue for everyone and your posts all imply a problem without either signposting the articles or summarising them.

I'll happily jump on your bandwagon if you help me to help you.

Eamonnogorman
I just did a quick comparison of my meter data against the GE data (for imported energy). The GE data was about 94-97% of the meter value, for each full day. I did have one day when it was just 75%, but that was because GE did not capture all of the data from my system, because of a network/communication issue.

Have you checked that your GE data is complete for each day? If you have an unreliable internet connection between your inverter and the GE servers, this could result in them reporting lower values than reality.

You're right Tim
The AMO list reverse running and I have asked them if there is a list of over running.
The MID meters are supposted to be unaffected by Conductive and EM emmissions, But it seems that several even on this forum still have problems.
We are on Photovoltaic and I compare the App figures against the Feed In Tariff meter. This meter has always been within 0.5% of the PV inverter reading. That is for nearly 11 years.
However the App always lags the FIT by some 10%. The Import values are around 30% higher than the GE App. The accuracy varies day to day with a max of 100% out.

Finding it impossible to get my Installer to check my figures.
Sorry, but I am not an Englander willing to accept being fobbed off. I want to know the truth.

I have not been inserting the Web links, as I'm not sure as how many people are interested.
There is quite a lot of heavy stuff out there and I don't want to be too much of a bore.
Another difficulty I have is my Android tablet, which is not very User Friendly when you try to cut and paste.

Interesting thread... So I just checked the last three full months of grid meter readings reported by the Givenergy cloud portal. These are meter readings set against 'Grid to Home' plus 'Grid to Battery':
October: 113.4% | November: 95.8% | December: 101.3%

(January to date is close to being accurate; the data sets aren't sufficiently aligned in time to be worth reporting.)
October grid import was 12 kWh, so I can take the percentage with a pinch of salt. I had another battery added in November so the system was down for a while - but the commissioning charge from flat on that day is shown in the portal and looks believable; November is a little short. However, I think we had a portal outage or two this month, so the data may well be under-reported.

So I thought I'll take a look at the solar reported by the Givenergy portal and compare what I see from my array inverter. These are inverter set against 'Solar To Home' plus 'Solar To Battery' plus 'Solar To Grid':
October 87.8% | November 91.6% | December 93.9%
OK - I can live with these numbers, I expect conversion losses of 10% and the drift to be bigger the more the generation is (i.e. October).

So for my own system the grid data is near enough, the solar is probably better reported by Givenergy (as my inverter data is 15 minute averaged). I can live with these results as they stand. CTs are OB115-Mod.