Snail Trails on Solar Panels

Snail Trails on Solar Panels

Installing solar panels to power your home can be a great long-term investment. It cuts down the cost of your utility bill and reduces your carbon footprint towards a better environment.

However, solar panels aren’t always problem free during their lifespan. which may disrupt energy production efficiency. One regularly encountered phenomenon is snail trails.

But what exactly are snail trails and how do they affect your solar energy system?

In this article, we go over the causes and effects of snail trails and how to prevent them.

What are snail trails on solar panels?

Snail trails are brown lines of discolouration that form on your solar panels after long-term usage. Solar panel snail trials are a phenomenon that has been reported since 2012 with occurrences increasing in the past decade.

The name “snail trail” is indicative of its resemblance to the slimy tracks left by snails. That being said, the issue isn’t caused by actual snails passing over your panels but a result of years of exposure to outdoor elements.

What causes snail trails on solar panels?

The root cause of snail trails can be attributed to faulty manufacturing blemishes. It is due to the degradation of EVA (Ethyl Vinyl Acetate) foil encapsulations in the solar panel, and the presence of moisture in the back sheet of the solar panels.

EVA foils degrade over time to form carbon dioxide and acetic acid. Moisture that seeps into the back of the solar panels undergo an unwanted chemical reaction with silver metal, carbon dioxide and acetic acid to produce silver acetate.

Silver acetate travels from the back to the front of the panel causing a chemical breakdown of the solar cells. This becomes visible in the form of brownish streaks or patches referred to as snail trails.

Do snail trails affect solar panels?

Reduced aesthetics

One consequence of snail trails on solar panels is reduced aesthetics. If you value the aesthetic appeal of solar panels, then the brown streaks and patches formed may be an eyesore. The visual aesthetic will only worsen with time. If that’s the case, you might consider replacing the deteriorated solar panels.

Reduced power production efficiency

A study comparing snail trail-affected and unaffected solar panel modules found a 9.1% reduction in power production efficiency in affected modules. This is because of the reduced irradiance due to the dark discolouration.

Snail trails are also a good indicator of microcracks, which are minuscule tears in solar cells. These cracks allow moisture to penetrate the interior of the solar panel (thus producing snail trails) but also cause the inactivation of solar cells.

An increase in the number of inactivated solar cells will subsequently reduce the energy production of your solar panel. Approximately 2 to 3% of power production efficiency is lost due to microcracks.

Read to learn ‘How to increase solar power efficiency’ 

snail trails
Photo by Alexas Fotos.

Causes the formation of hotspots

Solar panels generate an electric current when exposed to sunlight. The presence of snail trails and other damages can cause an increase in resistance within the electrical circuit.

Consequently, the circuit’s voltage rises, leading to the development of localised solar panel hotspots. This increases the risk of panels short-circuiting.

Hotspots look like burn marks on your panels and could be a potential fire hazard if left unchecked. It is advisable to replace your solar panels if you encounter this issue.

How to stop snail trails on solar panels?

Because snail trails can negatively affect solar panels, here are some tips on preventing them.

Develop better material combinations

In light of the snail trail epidemic, the materials used to make solar panels have been called into question. Normally, materials such as the EVA coil used in solar panels are designed to withstand high temperatures from exposure to sunlight.

Studies indicate that the EVA coil can have a lifespan of 20-35 years. However, with the increase in global temperatures, EVA coils are subjected to thermal degradation and produce the reactants that form snail trails.

Therefore, we have to rethink our approach to this issue. Scientific research is needed to develop a better thermal-resistant polymer alternative to use in solar panels.

Minimise the amount of phosphorus

Phosphorus has a significant correlation with the occurrence of snail trails. The high content of phosphorus is used in stabilisers and antioxidants for solar panels. Thus, one way to overcome the snail trail problem is for solar panel manufacturers to reduce the total amount of phosphorus in their products.

Handle panels with care to prevent microcracks

It was established earlier that microcracks can lead to snail trails on your solar panel. Solar cells are only 190µm thick and microcracks can be formed due to mishandling from transport and installation. Therefore, proper care when dealing with solar panels is key to eliminating the likelihood of any physical defects that might result in snail trails.


Snail trails can severely affect the reliability of your solar energy system. If you see streaks of brown discolouration on your solar panel, consider replacing them with brand-new modules or else, you might miss out on efficient solar energy production.

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