Rain Doesn’t Clean Your Solar Panels — Here’s the Scientific Reason

How many times have you heard: "No need to clean the panels, the rain is enough"? This saying is very widespread in Jordan — and it’s scientifically wrong and financially costly. Let’s understand what actually happens when it rains.

What Does Rain Actually Do?

Raindrops carry atmospheric dust and hit the surface of the panels. When they evaporate, they leave behind small circular spots of mineral salts and dried silt. Instead of cleaning the panels, rain actually adds a new layer of deposits on top of the existing dust.

• Rainwater isn’t distilled water — it carries carbon dioxide, salts, and airborne particles
• The water spots from evaporated rain gradually reduce the glass’s transparency
• Mud splashed up from the ground sticks to the frames and edges
• Green algae grow after every rainy season in humid areas

Numerical Studies from the Jordanian Market

Measurements taken on solar systems in Amman showed that panel efficiency dropped by 18% over 4 summer months without cleaning, despite being exposed to light spring rains. Panels cleaned every two months maintained efficiency above 95% of rated power.

In dry areas like Amman, infrequent rain isn’t enough to keep panels clean. Relying on it alone means a constant loss in output all year round.

Are New Panels Protected by a Special Coating?

Some companies market panels with a dust-resistant "self-cleaning" layer. This layer reduces buildup but doesn’t prevent it entirely, and it wears off over the years. Even these panels need regular cleaning to reactivate the protective layer.

What Is the Ideal Cleaning Schedule in Jordan?

• Summer (June – September): every 3-4 weeks due to intense dust
• Spring and autumn: every 6-8 weeks
• After every sandstorm or khamaseen wind: immediate cleaning
• After the rainy season (March – April): cleaning to remove rain spots