Cool sunny day generation lower than expected?

[MarcusMaximus]

I got my Tesla solar installation(3.8kW w/ 1 powerwall) fully turned on at the end of February. On partly cloudy days, I’ve seen the production go as high as 3.9kW(!), so all seems to be good there. On the flip side, though, on fully sunny days, it doesn’t seem to go higher than ~3.2kW, and that only for the absolute peak of the sun, for around 1/2 hour.

I was thinking it could be the panels heating up and losing efficiency that way, but the air temperature is still upper 50’s - lower 60’s. This is my first experience with a solar system so not sure if it’s typical or not. Apologies, by the way, if this is a stupid or common question; I did try searching for it but couldn’t find anything directly related.

 

[Sonus]

Yes, what you are describing is correct and the reason is that clouds diffuse the sun more evenly and due to the low efficiency of the panels partly cloud days will result in a better peak generation. Don't look at peak generation what you care about is your daily generation, the peak will be higher with little clouds but daily will be lower.

 

[DHevey]

Also, it depends on the orientation and angle of your panels. Your system should be most efficient when the solar angle matches the angle of your panels, especially if your panels are south facing. When I only had south facing panels, my peak production rate was in March and September, but the curve was narrower than in June.

 

[dhrivnak]

Another factor is on a sunny 55 degree day with little wind the surface of the solar panel is likely above 100F. They heat up fast in the sun which unfortunately negatively hurts performance.