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Checkout the 2 pictures posted with this thread. Very minor amounts of snow left on the top row of the 5th,6th, and 9th panels yet decreased production by 40% ish. Just found it interesting, warmer weather coming soon. 
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I would have thought modern panels should be able to do better than that....
What panel brand and model?
Any optimizers or micro inverters?
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What does the output for those panels (#'s 5,6 & 9) look like on a clear day this time of year compared to the other panels ?Comment
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Thank you.
I'm not surprised at the output decrease. anecdotally, my array's output with 2 strings of 8 panels each on a string inverter has each string's output die whenever any late afternoon shade gets to the.
Also, if that photo was taken midday, or even earlier (I suppose/maybe), there may have been (some) snow cover on those particular panels (slightly drifted up maybe ?) earlier in the day that could have melted. I saw a lot of that irregular drifting pattern when I lived in Buffalo.Comment
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It most certainly does! We finally have had some comprehensive snow fall this past week that covered our panels. The panels on greater slant on the side of the house cleared once the sun warmed them up (note: Don't stand under the panels...). I had to use a snow rake (rubber squeegee on a long pole) to pull the snow pack down. We went from under 2kW of power up to 7.25kW of power during peak daylight.
Rade Radosevich-Slay
Tiverton, RIComment
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To give an example to your question. All panels free of snow. Had a partly cloudy day today and as you can see the top row of panels are almost all the same. The left side of the bottom row falls off because of some late afternoon tree shading and is more noticeable on partly cloudy days this time of the year.
Screenshot 2024-01-21 at 6.47.48 PM.jpegScreenshot 2024-01-21 at 6.46.57 PM.jpegComment
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That's what I what I did and that's where the idea of selective (differential) snow coverage from drifting came from.
When was the last snowfall before the photo was taken, how much was it and was it accompanied with any wind that would produce drifting ?
Assuming the photo was taken around mid-day or so, if there is some additional (residual ?) snow on some panels in the morning from drifting (that had mostly melted before the photo was taken) and if the array is equally irradiated throughout the day, the additional snow on the drifted over panels will stay longer than on other panels and so reduce the day long totals for the drift affected panels.
I'd be interested to see any recent day-long totals from the array that starts and closes the day without snow on it.Comment
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