Panel Production Varies

[nairb]

Recently on most day my panels are producing about 20% less overall, on full sun days. I only look at full sun days since I'm aware clouds will cause variations in production. I have no obstructions (trees etc.) Very few days my panels will produce equally and fully among all of them, within a small percentage of each other. Most days, in the past couple months, the overall production is down about 20% compared to similar days of previous years, and around the same day of the month.

Something wrong is going on, but specifically, I'm wondering is someone may be able to shed some light on why the individual panels are producing less and not nearly the same on those low production days.

I've opened a case with SolarEdge, and they state it's weather or obstructions (which it is neither as I'm only looking at full sun days, and there are no obstructions) as they're showing the inverter with no errors and it is producing as it should.

As an example, I've included a screen capture of Oct 18 and Oct 19. The 18th the system is producing as it should. On the 19th something is happening and the panels are producing at different levels and less than the 18. Again, both days are identical full sun days. Not a cloud in the sky. The top image is the 19th, lower production, followed by the 18th, good production.

On the bad days there seems to be a cap of 2500 to 3000w, while on good days it will cap at about 4000w.

I can't seem to get SolarEdge to specifically look at this information and comment, although I will try yet again with them.

Any ideas what might be causing this?

Thanks!

Bad-Saturday-and-good-Friday-20241019-and-1018.png

[nairb]

After some back and forth communications with SolarEdge, they've stated "Tried checking the production of the each panels once again and noticed that a group of panels are producing about a 1/3 less than the others around it which could possibly be a bypass diode issue on the panels."

Not sure exactly what that means, but searching around is it possible a bypass diode is overheating causing the peak production time to decline. Again, any ideas or thoughts welcome. I've reached out to my solar provider but that is slow going.

[miogpsrocks]

What are these panels advertised rated watts?

[nairb]

300 watt, Silfab - SLA-M 300. Why?

[miogpsrocks]

300 watt, Silfab - SLA-M 300. Why?

Trying to figure out how much % is normal vs the rated capacity.

[nairb]

Trying to figure out how much % is normal vs the rated capacity.

Thanks, appreciate you taking a look. My issue isn't so much a percent of normal, since the angle of incidence for October is greater anyway, but the percentage variance from one panel to another. For example, looking at panel 14 vs 15, the difference when panels are all producing normally(18th) vs not(19th). On the "normal" production day all panels produce around the same, but on the other days they vary in production by quite a bit.

[Monstervi]

I had a similar issue with my panels a while ago where I noticed a drop in production on some full sun days. It turned out that over time, dust and dirt buildup on the panels, even though they seemed clean, was affecting their efficiency. I gave them a good wash, and the output returned to normal levels. A friend of mine in Dublin who uses solar panels Dublin had a similar experience, and they mentioned it really helped to have a proper cleaning schedule, especially during dry spells. Have you checked your panels for any dirt or debris? It might not be obvious, but even a thin layer can impact performance. Also, it could be worth checking the connections between your panels and inverter to rule out any issues there.