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No two meters are equal!

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Toodles
(@toodles)
Famed Member Contributor
6389 kWhs
Joined: 2 years ago
Posts: 1003
Topic starter  

When I first had my PV panels fitted in July 2022, the ordered Tesla Powerwall was not yet available as stock was short; as I wanted to know how much energy was being produced, I had an Enphase Envoy unit fitted and connected to the Tesla Gateway. I had Enphase data for individual panels (IQ7 microinverters) and the Enphase app provided production figures etc. Once the first Powerwall was installed, I also had the full data provided by the Tesla app - and the two sets of data were ‘similar’ for PV panel production figures. I also have the fitted ‘Import / Export Meter’ as seems to be fitted on every installation I have ever seen.

Last year, I started noticing that there were large discrepancies between the Enphase and Tesla figures for solar production; this seems to have started when an Enphase ‘Metering Error’ was flagged up. At the time, my installers could find no reason for this and requested Enphase investigate, they eventually came back to me saying that Enphase had found a fault and had updated the software then reset the error flag. I then noticed that the discrepancy in readings was nearly double on the Enphase report and have had their engineers here several times to investigate. Finally, the engineer found that a CT clamp that fed impulses to the Envoy unit had been connected around the two cables from the two strings of microinverters; the CT clamp was then clipped on further down the line after the two strings had been combined within the Tesla Gateway and then the data agreed with that of the Tesla app!

Now the two units agree very closely in their data reports, it only remains to know why these figures are noticeably lower than the export figures as shown by the SMETS 1 Smart Meter! I have questioned this difference with my energy provider three times and they assure me that the smart meter is working properly. I am not inclined to enquire further but just accept that there are readings and readings! Regards, Toodles.

Toodles, 76 years young and hoping to see 100 and make some ROI on my renewable energy investment!


   
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(@derek-m)
Illustrious Member Moderator
14399 kWhs
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Joined: 3 years ago
Posts: 4273
 

I have worked on complex instrumentation systems for over 50 years, and the worst thing that any system designer can do is provide two individual monitoring systems providing readings of the same variable. They will undoubtedly give different readings.

 


   
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Toodles
(@toodles)
Famed Member Contributor
6389 kWhs
Joined: 2 years ago
Posts: 1003
Topic starter  

@derek-m The man who wears a watch always knows the correct time - the man with two watches is never quite sure. 🙂 Regards, Toodles.

Toodles, 76 years young and hoping to see 100 and make some ROI on my renewable energy investment!


   
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(@derek-m)
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Joined: 3 years ago
Posts: 4273
 

Posted by: @toodles

@derek-m The man who wears a watch always knows the correct time - the man with two watches is never quite sure. 🙂 Regards, Toodles.

What about the man who doesn't wear a watch?

 


   
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(@mattc)
Trusted Member Member
242 kWhs
Joined: 6 months ago
Posts: 41
 

Posted by: @derek-m

What about the man who doesn't wear a watch?

He can have it written down on a piece of paper - guaranteed to be right twice a day

 


   
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Toodles
(@toodles)
Famed Member Contributor
6389 kWhs
Joined: 2 years ago
Posts: 1003
Topic starter  

@derek-m he carries a sun dial and when he can't see it, he knows it is time for bed.

Toodles, 76 years young and hoping to see 100 and make some ROI on my renewable energy investment!


   
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