Visually the solar panels you’ve invested your hard earned money into now look awful. In fact, by looking at what has occurred in the short time of being exposed to sunlight, you have every right to be concerned if your panels stand a chance of lasting the promised journey. As such the question arises, who’s to blame for solar panel discolouration? 

The manufacturer. Incorporating low quality components, solar panel discolouration is often the first sign of greater problems to come. The issue though, how would you be expected to know which manufacturers are likely to incorporate better materials? It comes down to rigorous standards supporting back-sheet selection which inevitably is the rear protective surface of your solar panels. Now there is resounding evidence that many Tier-1 labelled manufacturers are some of the biggest culprits.

Discolouring - Solar Review


Seek out solar panels by manufacturers which have a relentless back-sheet qualification process as the solar panel back-sheet is often the first component to breakdown when exposed to UV light. It is your right to know the details.


Discolouring - Solar Review

Let’s try to make it as simple as possible. Very much what appears to be a visual failure, discolouration or browning occurs when there is a yellow or brown discolouration of the Ethyl Vinyl Acetate (EVA) a result of two main causes. Solar panel discolouration is an uncontrolled chemical reaction amongst materials. 

Acetic Acid Formation.

An acetic acid formation is a major cause of solar panel discolouration. Several studies have confirmed that acetic acid formation causes the yellowing and browning of the EVA encapsulate. Solar panel discolouration often occurs on the PV cell surface in a chemical reaction involving the chemicals on the silicon cell surface and the chemicals used in treating the glass.

Exposure to Sunlight.

More commonly referred to as the back-sheet, the EVA is designed to enhance the resistance to UV radiation and prevent browning. When a low quality EVA is used, the structure of the EVA is altered when exposed to heat and UV radiation. As a result, the EVA starts turning to a yellow or brown colour. Solar panel discolouration (yellowing and browning) occurs when exposed to sunlight in the first few years.


Discolouring - Solar Review

Aside from the visually displeasing side-effects, solar panel discolouration will present far greater impact than first thought. 

Reduced Performance.

Solar panel discolouration in an evolved state will lead to a depreciation in electrical performance thereby leading to power loss. The increases in heat absorption from the solar panel discolouration promotes a more resistive electrical circuit and further enhances the browning process.

Advanced Degradation.

During degradation, as the EVA starts to change from a white colour to a brown or yellow colour. The EVA is experiencing a chemical reaction that produces acetic acid. This further breaks down the UV absorber and the gel content increases. Evoking a form delamination, the degradation in the EVA can promote an environronment which can promote cell corrosion.


Discolouring - Solar Review

Delve further into the EVA durability before purchasing the solar modules to help safeguard against the likelihood of solar panel discolouration. Go one step further and avoid a solar panel with an EVA back-sheet all together. 

Glass-glass or double glass solar panels available from selected manufacturers utilise a rear glass protective sheet in place of an EVA. Although slightly more expensive, the beauty of glass, it will not degrade. None-the-less the over whelming majority of solar panels are comprised with an EVA back-sheet due to affordability. As solar panel technologies advance with a focus on higher power efficiency, the quality and durability of the EVA must not be forgotten. 

Still thinking?

Did we get you thinking? If so, leave your thoughts below in the comments section. 


  1. Yes, you’ve got me thinking! I am currently working through solar quotes and I am only considering Tier 1 panels. I wouldn’t have thought this type of issue would apply to Tier 1 panels so I’ll be checking if the panels I am considering have these back-sheets, especially given some are more expensive than others. Thanks for highlighting this issue!

  2. Although I think I got a lot out of beneficial information out of this article, I also got confused. It almost seems like you have said that if a panel manufacturer is deemed to be tier one and/or they sell a lot, they must make rubbish panels.

    • Not quite, at the end of the day each panel (not manufacturer) should be assessed on it’s own merits for any given project. The main objective behind these particular posts is to raise awareness around the marketing deception promoted by low-end retailers brandishing the term Tier-1 in order to coerce a sale.


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