How are my Rooftop Solar panels performing after more than a decade?
Last winter, I reached the 10-year mark with my SolarCity (Now Tesla) solar panels and decided to analyze my production figures to determine if my panels’ performance had declined.
If you are interested in my cost calculations and savings for going solar, you can read my previous essay here. And yet another essay (link) of mine examines the peaks and valleys of solar production (by day) and calculates the total battery capacity needed to go fully off the grid. If you are interested in the raw data of this article, please contact me through the article’s comments.
The Data
My system specs are:
Below are the total annual production data for this system:
And below are the annual percentage changes from year over year:
Conclusion
As observed in the preceding graphs, there is no discernible negative trend, which would be the case if the system’s performance were declining gradually, everything else being equal. Since the system is static and I am averaging daily data across a year, which is a big enough range to allow for variations in weather conditions, I assume that everything else is indeed equal.
Any degradation in PV performance must be gradual, and it cannot explain the rising trend shown in three of the last eight years, unless those years experienced extreme weather events, such as abnormally high sunny days. However, for the sake of mathematical fun, the average annual change was a negative 1.28 percent, although I am unsure of its significance at this point. must determine if this tendency continues.
In conclusion, the system has not deteriorated dramatically during the past ten years.
