Don’t use dish soap to clean solar panels, study warns

Julianna Varjopuro sprays the solar panel with a standard glass and mirror cleaner (Mellerud brand was used in the study), which was found to be almost as effective for the studied type of solar panel as a commercial product specifically designed for cleaning solar panels. Credit: Mikael Nyberg.

A recent study from the University of Turku in Finland shows that cleaning solar panels with dishwashing detergent can actually make them less efficient.

The research, presented at a major European solar energy conference, explored how different cleaning products affect the glass surfaces of solar panels.

For solar panels to work well, they need to absorb as much sunlight as possible.

Dirt and damage to the glass can block light and reduce their ability to generate power.

The team at the University of Turku tested several cleaning methods to find the best way to keep solar panels performing at their best.

Most common cleaning agents, such as glass cleaners and isopropanol, were safe to use on solar panels.

However, the study found that dishwashing detergent is not a good choice. Surprisingly, even dirty glass let more light through than glass cleaned with dish soap. This means that using dishwashing detergent can make your solar panels less effective, even if they look clean afterward.

The problem isn’t that dish soap damages the glass itself. Instead, it seems that rinsing isn’t enough to completely remove detergent residue. This residue blocks some of the sunlight from reaching the solar cells, reducing their efficiency.

“Solar panels often have a special anti-reflection coating on the glass, and it’s important not to damage it,” explained Professor Kati Miettunen, who led the research.

“We didn’t test things like pressure washers, but I would avoid using them on panels as well.”

Research Assistant Julianna Varjopuro added, “Even if the glass looks clean after using dishwashing detergent, its ability to let in sunlight is still reduced. A clean appearance doesn’t mean the panels will perform well.”

The study, carried out by the Solar Energy Materials and Systems (SEMS) research group, provides important guidance for solar panel owners. It highlights the need to use the right cleaning products to maintain the efficiency of solar power systems.

As more people switch to solar energy for a greener future, knowing how to care for panels properly is crucial. The RealSolar project, which is part of this research, aims to support the use of solar power in Finland’s energy system, helping ensure an equitable transition to clean energy.

Source: University of Turku.