Why You Shouldn't Clean Solar Panels with Dishwash Soap

Using standard dishwashing liquid to clean photovoltaic (PV) modules can quietly degrade their energy output. A study led by the University of Turku revealed that while dish soap makes glass look spotless, it leaves behind microscopic residues that impair light absorption and reduce overall solar efficiency.

Key Findings

• Safe Cleaners: Most common household solvents—such as isopropanol, ethanol, acetone, standard glass cleaners, and dedicated solar detergents—caused no harm to light transmittance.

• The Problem with Dish Soap: Dishwashing liquid altered the optical performance of the glass. Even thorough rinsing failed to restore the surface to its original light-transmitting levels.

• Invisible Residue: The degradation is not caused by surface etching or permanent destruction of the anti-reflective (AR) coating, but rather a persistent chemical film that blocks sunlight.

The Experiment

Researchers tested solar panel glass by soaking it in different cleaning agents for 20 hours. The result? Only dishwashing detergent caused a measurable drop in light transmission. To keep your system running at peak capacity, stick to pure water, specialized PV cleaners, or approved alcohol solutions.

• Test Method: Unused silicon solar panel glass was immersed in various cleaning agents for 20 hours.

• The Result: Dish soap was the only cleaner that consistently impaired light transmittance.

• Best Practice: Clean panels using only water, manufacturer-approved PV formulas, or standard alcohol-based cleaners.