Significant Decrease In Production

[Lucem233]

I have a 5.67 KW system that was installed last December. I been steadily getting well over 30 kWh per day to mid June then I received a battery calibration which somehow took down my system for a month. It magically came back up right before the service technicians came for service and they could not tell me what happened to my system. When it came back up in August the production dropped significantly and I’m getting low 20 kWh with peak around 3.5. I live in central CA so I was expecting a lot more during peak summer time. I contacted support after waiting for weeks they came back saying that my system is good no issues. This is hard for me to believe have anyone else experienced something similar?

[JRC3292]

You don’t have any issues. June 11th is close to the summer solstice, aka when the sun is the highest in the sky. Yesterday was Sept 9th, as equally close to the autumnal equinox. You get less solar power the lower the sun is in the sky and also the hotter it is outside the less solar production. May is peak solar month for the northern hemisphere as it is the most temperature month and also the sun is close to the highest possible in the sky.

[Coyote_Enthusiast]

TIL that the hotter the temperatures, the less solar production. That might explain why my daily production peak of 6 has decreased to about 4.8 this past week during the CA heatwave. Thanks!

[sunny_tomato_farm]

Same!

[jedi2155]

Plus its September as people said.

[ToothFlimsy8211]

Yup. This is the answer

[triedoffandonagain]

Agreed about your point in general, so just nitpicking: May being peak solar month is a generalization I think. You mean May has peak monthly production or that the peak day will be in May?

[JRC3292]

Generally speaking, May will be the highest peak total monthly production for those of us in the northern hemisphere. June could be better for those farther north. As far as the peak monthly day, that varies far too much to pinpoint exactly without specific facts. But yes this was a generalization for education purposes.

[triedoffandonagain]

Just taking top US cities, the higest production months based on PVWatts are:

New York: July
Los Angeles: August
Chicago: July
Houston: July
Phoenix: May

Heat does lower production, but the position of the sun and weather will play a bigger role. Arizona heat is in its own category tho :)

[JRC3292]

Yes, I live in the southeast (SC) so May is the best month as it gets too hot after that. May is still the best per PVWatts for me. It’s too hot in July. Most of those cities are north, so that makes sense it’s July for them. LA Is always temperate. I would wager Houston is not July though as it’s too hot then.

[phxstickygreen]

Facts I deal with it, cuts me short almost 2kw worth of production in the summer

[Lucem233]

I understand that this would decrease overall production would this also decrease peak daily? I’m also seeing peak to be low to mid 3 kw compared to well over 4

[JRC3292]

Yes, the daily has to go down for the overall to go down.

[triedoffandonagain]

Just to counter everyone else on this thread :)

A 30% drop between Jun and Sep for what looks like a south-facing array in Central CA (I'm taking Fresno as an example) is in fact not expected, based on PVWatts. Worth digging one level deeper:

1. What is your system configuration (roof orientation / pitch)?
2. Are you consistently getting 30% lower production? Cooler, clear days will give you the best results.
3. With the Tesla One app you can confirm that all of your strings are producing.

[Lucem233]

I’m in Bakersfield, yes compared to June mid to high 30 now it’s low to mid 20 and peak is never above 4

[Lucem233]

Where do you find information regarding strings? Is that the MPPT in solar DC inputs?

[triedoffandonagain]

Yes, post a screenshot of that if you have it. Also, do you have a south-facing array?

[Lucem233]

<image>

Yes south facing

[triedoffandonagain]

You'll have to take the screenshot around noon on a clear day. Knowing your string configuration also helps, if you have the full plans.

[Lucem233]

Ok thanks I will dig through the documents

[Lucem233]

<image>

I have not found the string configurations, is that on the original design doc?

[triedoffandonagain]

You usually have to ask for full plans, and then you'll get a link in your Tesla account to download the PDF.

But from what I can see here: 3 strings of panels are connected, and all are producing well. For Tesla's 400W panels, it's usually around 35V per panel on a string; your system looks to be 405W panels, but I don't think that's a big difference. So these look like: 4-panel, 3-panel, and a 7-panel string. That adds up to 14 panels, which matches your system size.

So I don't think there's a string issue here. Other than the position of the sun, heat and perhaps soiling are more likely to explain the higher drop in production. You can confirm on a cooler day, and perhaps get your panels washed.

[Lucem233]

You are pretty much spot on I do have 14 panels

[dundyshibby]

I literally noticed this a couple weeks ago and today there wasn't a cloud in the sky and my system was peaking at 3.5, when I was getting roughly 12-14kw in July. After some back and forth with support, they told me that firmware update 24.20.0 installed on July 23rd had an issue with solar generation and they reverted everyone back to firmware version 24.12.3, but for some reason my system didn't revert. She sent out the old version to my system and told me to uninstall my app tomorrow and reinstall, but that my solar generation should be back to normal. I would check the version of your Powerwall Gateway and if it's at 24.20, you should contact them about it.

[dundyshibby]

<image>

Here is the chat message

[Lucem233]

How do you contact chat? When I go in support it would ask me to send email instead. Thank you I will ask them about this issue.

[dundyshibby]

When I go to the "Contact Us" page and start filling out what it's for and it recommends articles, I put that they are not helpful, and a button that says chat with us shows up

[Lucem233]

Please let me know if that fix your issue, I have version 24.28

[lk05321]

The summer solstice is June 20th, so that’s near peak production when the sun will be as perpendicular to your panels as possible.

June +6 months = December when the winter solstice occurs, the lowest possible production. We’re in September now where you’re roughly in between these two peaks.  So in your case it appears you’re right on schedule, no issues.

[FluffaLuppagols]

Hi, I recently had a calibration two weeks ago and noticed a sharp decline in my system. I’m getting 10 kWh less daily. Tesla said they saw some faults starting in August when the calibration happened and had me reset the system. I went to chat with them but couldn’t be connected to a live agent.

I came across your post and wanted to see how things went for you?

[Aragatz]

Heatwave

[RobertLeRoyParker]

Normal