Solar production dropped ~33% after Tesla technician visit?!

[sovietaced]

Hello. I recently had an 11.2kW system installed with two PW+ on 6/26/2023. At the moment I am still waiting for an inspection to happen to the system is in self consumption mode.

For roughly a month after the installation I was seeing fantastic production numbers. Peak output was roughly 13.2kWh and total output was > 100kWh each day. On July 25th a Tesla employee arrived to the house completely unannounced to finish something. He said I would be out of power for a few minutes. That morning my system was already producing 11kWh at ~10:30AM and after the visit I have never seen production greater than > 8.5kWh ever again. I expressed my concern with this while he was at the house and explained how self consumption works (yeah I know) and basically told me to keep an eye on things but wait until PTO.


Day before Tesla visit

Day of Tesla visit

It has been almost a month since this day and again, I have never seen greater than 8.5kWh (and this may have been a spike related to partial cloud cover). Below is a picture of what my production looks like, with me charging my Tesla Model 3 + PWs and outstripping the supply of the solar panels.

I don't believe that my solar production would drop 33% due to natural causes overnight and the production seems directly tied to the technician visit. I'm wondering what the community thinks about this. I am obviously quite a bit concerned because this is a fairly significant investment and 33% production loss is a very significant amount.

As of recently, I have setup the Powerwall Dashboard to collect more details about what is going on and I don't see anything clearly broken, just feels that overall production is lower than it should be. There are some alerts but I'm not sure if they are noise. Below is my configuration with 28 panels. It seems that the top right cluster of panels is string S3 and S4. Bottom right is S2. Bottom left and top left are S1A/S1B?

Looking at the Grafana dashboard it just seems like each panel is peaking at ~300w out of the 400w max rating per panel.

South East Facing (peak in AM)
String A (7 panels) peak at 2.19kW / 2.8kW
String B (6 panels) peak at 1.92kW / 2.4kW
String C1 (3 panels) peak at .914kW / 1.2kW
North West Facing (peak in PM) (I realize I capture these values too soon)
String A1 (6 panels) peak at ~1.6 / 2.4kW
String B2 (6 panels) peak at ~1.6 / 2.4kW

Any guidance would be greatly appreciated thank you.

 

[offandonagain]

Your early production numbers look wrong for a few reasons:
- An 11.2kW system will not exceed its rating like you were seeing. You might get close to to that number around summer solstice and if all panels were facing south, neither of which is the case for you.
- All of the production going to the house and none to Powerwall seems strange.
- Both of these indicate that something was off with power monitoring (CTs), which is probably why the visit was necessary.

The more recent production is what you should expect. You can plug your system configuration into PVWatts to see the expected production by month or by hour.

Also note that before PTO you're not allowed to export to the grid, so once your Powerwalls are full your solar generation will be limited to what your house uses (that's the steep drop-off you can see in the afternoon). Once you get PTO and start exporting to the grid, you'll see your daily production go up. But the peaks will be similar to what you're seeing now.

 

[holeydonut]

Your early production numbers look wrong for a few reasons:
- An 11.2kW system will not exceed its rating like you were seeing. You might get close to to that number around summer solstice and if all panels were facing south, neither of which is the case for you.

@sovietaced any chance you have the order details or design of your system so we can see your inverter(s)?

I agree with offandonagain... Tesla likely installed a 7.6 kW-AC inverter. If so, the original screenshots don't make sense because there'd be no way for the system to be generating so much.

 

[jjrandorin]

I think what @offandonagain said, that there was no way for those original numbers to anywhere CLOSE to being correct, which is what prompted the visit, and the more realistic numbers.

There isnt any way for a 11.2kW system to produce more than that. Probably incorrect CT placement leading to numbers being doubled that should not have been.

 

[taphil]

Agreed. Your early numbers were wrong. A 11.2kW system, at this time of the year, under ideal conditions and panel orientation, would produce maybe 65-70kwh at most.

 

[sorka]

For comparison, my 13KW system has panels all facing south with no shading and I made 74 kwh yesterday with no cloud cover.

 

[sovietaced]

Your early production numbers look wrong for a few reasons:
- An 11.2kW system will not exceed its rating like you were seeing. You might get close to to that number around summer solstice and if all panels were facing south, neither of which is the case for you.
- All of the production going to the house and none to Powerwall seems strange.
- Both of these indicate that something was off with power monitoring (CTs), which is probably why the visit was necessary.

The more recent production is what you should expect. You can plug your system configuration into PVWatts to see the expected production by month or by hour.

Also note that before PTO you're not allowed to export to the grid, so once your Powerwalls are full your solar generation will be limited to what your house uses (that's the steep drop-off you can see in the afternoon). Once you get PTO and start exporting to the grid, you'll see your daily production go up. But the peaks will be similar to what you're seeing now.

When the system was originally installed it was in a weird state where it was operating like it has permission to export, but the app was reporting that the power was being sent directly to the house. Not sure why, but this occurred for about two weeks until the Powerwalls were activated (July 8th), which is why I included the screenshot from July 24th (which is when the power walls were enabled but I was still seeing high numbers).

I understand the bit about self consumption mode (prior to PTO), which is why whenever I'm evaluating the peak output I plug in the model 3 and charge at 48A to introduce a high load.

 

[sovietaced]

Thanks for the guidance everyone! I guess I'll just have to get used to the real numbers

 

[sovietaced]

@sovietaced any chance you have the order details or design of your system so we can see your inverter(s)?

I agree with offandonagain... Tesla likely installed a 7.6 kW-AC inverter. If so, the original screenshots don't make sense because there'd be no way for the system to be generating so much.

The system has two 7.6 kW inverters, one on each power wall.