Why is that always posted without stating the magnitude of the effect? The numbers that you find online are around 15% relative loss at 60°C vs. 25°C panel temperatur (I remember a HN comment reporting 12% comparing peak April to peak July). That is significant, but not world changing, especially for AC.

What about panel degradation?

There are 30 year old still functioning panels in Australia.

Buried in that longevity, is an observation that a fifth of panels degrade faster than expected

  The long tail appears on graphs showing the degradation rate per year of the panels, indicating that up to 20% of all samples perform 1.5 times worse than the average.  

See (Uni NSW study) Cracking the ‘long tail’ problem: new research targets hidden solar panel issue (2026) - https://www.unsw.edu.au/newsroom/news/2026/01/research-targe...

and discussion: Maximising time in the sun: how to maintain and repair solar panels to make them last (2026) - https://www.theguardian.com/australia-news/2026/feb/13/maxim...

This is more about the lifetime of many PV panels in Australia (temps to 45 C so far) not specifically about PV panels with many hours at > 50 C.

It exists and does degrade panels but the time horizon is pretty wide. Real world data shows something like 0.5% to 0.7% degregation per year on average. At the start the degregation is higher and but it slows down with age.

So a 20 year old panel might be at around 80% in the worst case. Often they are in much better shape. This seems like a pretty good deal to me.

Marginally. Between 77F and 100F you only lose about 5%, so you still get 95% of the stated max efficiency. It’s basically negligible and not really relevant.

Panels are cheap, efficiency is not that important.