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This question is focused on high quality solar panels (certified Tier 1) which are more and more mainstream. The 25 years warranty is becoming standard, and producers describe degradation in 25 years charts. What happens after 25 years? Is degradation expected to be constant for another decade or two, or is there some likeliness of speeding up and falling down from linear progress? Sure total panel failures can be expected too, and estimate of that can be included to make the picture more robust. Anyway, how do solar panels degrade after 25 years of warranty?

LG:

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SunPower:

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  • Maybe we can only start answering this question in 25 years and 1 day (or more seriously, in about 30-35 years)? – gerrit Oct 20 '20 at 7:47
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    @gerrit I am sure they did not test the current panels 25 years either, still they came up with 90.8% after 25 years :-) I am sure people in the industry can give us decent estimate based on their observations for longer time, even though with higher statistical bias. – Miro Oct 20 '20 at 8:02
  • Those are estimates, and manufacturer estimates at that. Time will tell if they live up to the claim (and if the company will still be in business in 20 years to handle warranty claims if they don't). – gerrit Oct 20 '20 at 8:53
  • @gerrit Agreed. All I am after is extending these charts by another 20/30 years to see what producers expect to happen there. I am aware the best I can get is educated guess. – Miro Oct 20 '20 at 16:00
  • The U.S. National Renewable Energy Lab has a project studying PV degradation rates. If I get a chance I'll attempt to summarize into an answer. – LShaver♦ Oct 20 '20 at 18:29
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When semi-conductors get hot, the impurities that make them work move around somewhat. Solar cells are very carefully made layers of silicon with very controlled levels of impurities.

With enough time sitting on a hot roof, this gradual diffusion starts to affect the back leakage rate of the cell.

Those cells are connected in series, then the series units are connected in parallel. That a lot of connections. With time and weather, connections corrode. solder joints crystalize.

A 25 year warranty limits their liability.

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