Solar panels marketed as "self-cleaning" which they Don't! Have a hydrophobic surface that prevents water droplets from sticking to them. While this is a beneficial feature, it does not equate to maintenance-free upkeep of the panel.

Rainwater simply is not enough to keep solar panels clean and running optimally.
Just think of your car windscreen - if you were to leave it unwashed for six months, how much visibility would you lose? Grime and debris can cause a film that blocks light from entering the panel, resulting in decreased energy
production and missing out on potential financial returns. The same elements that affect your car's windscreen are also at work on solar panels. Even though rain cleans the middle of the panel to some degree, dirt accumulates around the edges where wipers do not reach. So even with rainfall, it is essential to clean and maintain solar panels for optimal performance.