Underperforming panels

[silverhorsefarm]

What would be the most likely explanation for my Schuco 180 panels never topping 150 watts of output? We've had many relentlessly cloudless days and the panels all seem stuck in the low 100s to a high of 150 watts. My array points directly to solar south and it is completely unobstructed.

[Sunking]

Pretty simple really as the rating is a STC lab rating, not a real application specification. A STC rating is made in a lab with a 10,000 watt lamps perfectly aligned with the panel facing directly into the lamp and refrigerated to 25 degrees C in a vaccum void of mosture.

In the real world yourrpanel never faces directly into the sun with no atmosphere. at exactly solar noon with the sun directly overhead in a air conditioned envoroment.

For example3 as the tempurture rises the power output goes down. It is hot right now. So what you are seeing is nornmal and expetected.

[silverhorsefarm]

Thanks for the quick answer. I guess I assumed that the ratings were more realistic - e.g. ideal field conditions. My roof is also at 34 degrees and we live at 39 degrees latitude, so that could be part of it....

[peakbagger]

Wait for a cold sunny day with snow on the ground, you most likley will see more than the panel rating.

[russ]

It would be interesting to see the watts/m2 reading from a weather station in your area.

I doubt that it ever comes close to 1000 from my observations. Maybe I can find something on wunderground.