While Virginia receives about 43 inches of annual rainfall, research has definitively shown that rain alone is not sufficient to keep solar panels clean and operating at peak efficiency. Rain can wash away light dust, but it cannot remove stubborn soiling like pollen, bird droppings, tree sap, and cemented debris.
National Renewable Energy Laboratory studies found that even after pollen season ended, solar panel performance did not return to previous levels despite frequent rainfall. The problem is that panels cool down at night and attract morning dew, causing dirt and debris to undergo a cementation process that literally bonds contaminants to the panel surface.
In Free Union’s tree-rich environment, panels are particularly susceptible to organic debris that rain cannot effectively remove. Additionally, panels installed at low angles or in shaded areas receive less natural cleaning action from rainfall and require more frequent professional maintenance to maintain optimal performance.