Tesla app graphs wrong - Which CT is misplaced?

[jamesb2147]

Let me illustrate my point with some images.

These are from back in late May but behavior has been the same since system install in Spring 2022. Interestingly, the grid import/export numbers do roughly match the utility's reporting, and the solar production graph seems to accurately reflect sunshine. Additionally, the Powerwall graph is likely accurate.

However, I can assure you my home's usage is NOT zero in the middle of the day. I figure it's likely a misplaced CT, but perusing the installer guide this isn't super obvious. Anyone have experience or knowledge to share so that I can fix this? I'm happy to learn!

 

[jamesb2147]

Some details for context:

I have a non-Tesla solar setup. Panels (I think REC..?) with IQ7+ micros and I think it's 8kW total (small house, not a ton of roof) in panels. 2 Powerwalls installed for whole-home backup using Tesla Gateway 2, I believe. One factor I did not mention is there's also generally a factor of 2 discrepancy between what Tesla reports the solar produced and what Enphase says was produced. You can see in the solar screenshot above it says 24.7 kWh while Enphase for that same day says 47.8 kWh.

I'm not concerned with getting my solar production numbers correct in the Tesla app per se, but I would really like to have a good handle on what the house is using so I can better manage it. I mention the solar production discrepancy as it might be revealing about what the underlying issue is.

 

[miimura]

In the Powerwall system, the home consumption is calculated according to this formula:
House = Solar + Grid + Powerwall
The Powerwall flow is reported directly by the Powerwalls, so they are almost never in error. However, they take their command to charge based on the solar production calculation. So, it is very likely that your 1/2 solar production measurement is causing your Powerwalls to only charge with 1/2 power and the rest is going to the house and being exported to the utility. This causes the calculation of the House usage to be negative, so it just renders it as zero since it makes no sense for loads to be negative.

The Grid and Solar are measured by CTs. There are lots of ways that they can be placed or configured incorrectly. Most notably, you can use either one or two CTs to measure the solar circuit since it's a pure 240V circuit and there is either no current flow on the neutral or the neutral is not connected at all. Therefore, there is a configuration item to double a single CT so that the wattage calculation is correct. If you use two solar CT's they both have to be facing the correct direction so that they don't cancel each other out.
If you are comfortable doing to, I would look inside your Gateway and the breaker panel where your solar breakers are installed and see if you have one or two solar CTs. Then you will have to have the solar configuration in the Gateway fixed by the installer or by Tesla. I have never tried to DIY changes to the Gateway config using the installer interface, but I think I have read about people doing it. Good luck.

 

[jamesb2147]

Indeed, it does look like the home consumption is negative... it would appear that the reported solar output is entirely going to charging the batteries with excess hitting the grid, and that's leading to the home using negative energy.

An excellent diagnosis! I'll be checking out the panel physically when I get a chance and will report back here with results. Hopefully I can figure out the installer login on my TG2 as well, assuming your theory is confirmed once i pull the panels.

 

[miimura]

This makes perfect sense. In the image above, you are actually producing 5kW solar, battery is charging 2.5kW, house is consuming 1.0kW and you are exporting 1.5kW.

 

[CrazyRabbit]

Please post your tesla wiring diagram/drawing. Please post pictures of your system with face plates removed.

You can tap the three vertical bars (by day) to show more details in the app.

 

[jamesb2147]

Update: I did not end up removing my panel cover. I pestered my installer as well as Tesla. After a couple of weeks of radio silence from Tesla, it looks like my solar production numbers were silently doubled 2 days ago. Everything is finally adding up sensibly! Thanks so much for the help!!