With the recent rains in Southern California, people often wonder if rain is enough to clean your solar panels? Although rain will provide a minimal rinse off any loose dirt or dust, it will not remove the baked in dirt and debris. To illustrate this, consider what would happen to your car’s windshield if you didn’t clean it for 6 months? The grime and dirt would “green over”, completely blocking your visibility (and light) from entering your car. Think about how dirty your car/windshield gets even after several weeks. And the morning after a rain, remember how your car (if left outside) seems even dirtier than before, like the dust and dirt was just moved around. The fact is that rain contains dust particles that settle and attach to the surface after the rainwater evaporates. When we use our windshield wipers, we clean the center of the screen, but where the wipers do not reach, there is a nasty film of dirt. Your solar panels are in the same condition as the edge of the windshield, where the wipers can’t reach, and likely even worse, since the angle of most solar panels is less than your windshield. Also, the minimal loose dust that does move by the rain will lead to dust accumulating in the lower row of each solar panel, which can cause significant heating. In a string of photovoltaic cells in a panel, if one cell is shaded the others will force current through it, which makes the cell heat up, and will cause a significant decrease in your solar output and greatly reducing the lifespan of your panels.
We’ve recently cleaned many homes/businesses shortly after a rain and the before pictures are just as bad as we find them in the middle of summer! And our customers routinely report a 15-20% boost in their power output after having their panels cleaned, even days after it rains. See photos below of some panels we cleaned shortly after it rained then you decide if you think rain is enough to clean your panels …
Look at the dust accumulating on the lower row/section of the panel after the rain!
Just a few days after it rained, this home had a tremendous amount of “baked in” dust accumulation. This looks like my car after it rains!
These panels were cleaned on February 6, just several days after it rained. The top section is after SolarTidy cleaned the panels. The bottom section is how well the rain cleaned the panels “naturally”.
And here’s the results from one customer who had their panels cleaned by SolarTidy on January 31. After the cleaning, his net energy use went negative, meaning he was generating more energy than he was using. It wasn’t the rain that got him more energy output!