Solar Panel Output Degrades/Reduces over time - How Much?

jimjames

I thought it might be interesting to revisit this 5 years on.

Over 13 years now we've averaged 3253kWh from our panels each year. The last 2 years were below average but 2022 was the best year ever at 3522kWh so I don't think I can see anything beyond the weather variation at the moment. Jan & Feb this year were very poor but March has been the best output for the month in the last 13 years by some margin.

NedS

To add, modern panel technology is improving too, with modern panels now citing 0.25% annual degradation potentially giving 92% capacity after 25 years, so well within the confines of annual solar irradiation variance

Screwdriva

This NREL report highlights a factor that should be quite a bit more obvious - panel performance degradation is directly linked to the quality of the manufacturer. Admittedly the panels tested are obsolete today but I would challenge the presumption that things have suddenly improved dramatically since. 

https://www.nrel.gov/docs/fy22osti/81172.pdf

Exiled_Tyke

jimjames said:

I thought it might be interesting to revisit this 5 years on.

Over 13 years now we've averaged 3253kWh from our panels each year. The last 2 years were below average but 2022 was the best year ever at 3522kWh so I don't think I can see anything beyond the weather variation at the moment. Jan & Feb this year were very poor but March has been the best output for the month in the last 13 years by some margin.

  After reading the latest posts on this thread today, I thought I'd have a look at my generation figures.  I'm pleased you reported a great 2022 followed by poor 23 & 24 as that's what my figures show.   My conclusion from this is that there is no obvious degrading with my (LG) panels over the first 9 years.  

Waywardmike

I've checked my spreadsheets and if I apply a trendline to my readings over the last 10 years I do get a slight negative trend. Bear in mind that if I remove last year the trend is positive.

The system consistently performed well above PVGIS estimates year after year (103-120%). 2018 is omitted from the data as we had scaffolding covering our roof for three months.