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Common Solar Panel Defects: Solar Panel Discoloration & Delamination

Updated: Apr 20

common solar panel defects

Solar PV project underperformance is a growing issue for solar energy system owners. According to Raptor Maps data from analyzing 24.5 GW of large-scale solar systems in 2022, underperformance from anomalies nearly doubled from 2019 to 2022, from 1.61% to 3.13%. Solar panel underperformance from equipment-related downtime and solar panel defects is increasingly common as PV systems age.

Unfortunately, these issues have a substantial financial cost. The estimated annual revenue loss from the 24.5 GW from the study sample was $82 million, indicating a $2.5 billion loss for the entire solar energy industry. In addition, there are numerous other risks that could hinder solar system performance, according to the 2023 Solar Risk Assessment. Extreme weather risks, more solar systems in harsh weather environments, and the difficulty of predicting equipment-related performance are important factors.

Thus, solar power professionals need to be knowledgeable about common solar panel problems to better service solar clients and prevent underperforming solar assets. Regular maintenance and performance modeling can help prevent revenue loss for solar system owners through early detection and corrective action. Let’s examine how to know if a solar project has a performance issue, as well as common solar panel defects, and how to resolve them.

Components of a Solar Panel

A solar panel comprises several key components. Understanding the parts is helpful in understanding solar panel defects.

Solar Cells: These are the key photovoltaic (PV) components that convert sunlight into electricity.

Frame: The solar panel frame provides structural support and protection for the solar PV cells.

Glass Cover: A tempered glass cover protects the solar cells from environmental factors while allowing sunlight to pass through.

Encapsulation Material: This material protects the solar cells from environmental damage, boosts solar panel durability, and helps manage temperature.

Solar Panel Backsheet: A layer on the backside of the solar panel that provides additional protection and insulation.

Junction Box With Diodes: This box on a solar panel contains electrical connections and commonly includes bypass diodes to optimize performance.

Solar Panel Diodes: This essential semiconductor device that prevents reverse current flow, ensuring the optimal performance and safety of the solar panel system.

Busbars and Ribbons: These conductive strips help collect and transfer the electrical current generated by the solar cells.

Anti-reflective Coating: Applied to the glass cover on a solar panel to reduce reflection and enhance light absorption.

How To Spot Common Solar Panel Defects

There are several tell-tale signs from reviewing solar monitoring data or visual inspections that solar panels are underperforming. A significant drop in energy production compared to the PV system's rated capacity clearly indicates underperformance. Monitor solar energy production regularly and compare it with the expected output.

Keep in mind, however, that atypically hot or cloudy weather can also cause temporary underperformance issues, as excessive heat or cloud cover can reduce solar panel production. In this case, no corrective action is needed – just patience.

Dust, dirt, or debris accumulation on the panels can reduce efficiency. Similarly, shading from nearby trees or buildings can cast shadows on the panels and hinder their performance. Cracks, chips, or other visible damage on the panels' surface can affect their ability to convert sunlight into electricity. Likewise, electrical problems with the system, such as loose connections, faulty inverters, or malfunctioning wiring, can lead to reduced performance.

solar panel diode failure

Identifying Common Solar Panel Defects

There are a variety of equipment anomalies that result in lower power generation caused by poor soldering, lamination quality, cell design, quality control, frame or glass construction, busbar corrosion, and junction box defects. Proactively addressing such issues from routine maintenance, inspection, and reviewing solar monitoring data can help mitigate issues.

Often, defects are visible during a visual inspection because solar panel discoloration is apparent. Read on to learn about some of the most common problems with solar power panels that can impact their lifespan.

Common Solar Panel Defects & Discoloration

Causes Solar Panel Defects

Snail Trails

This occurs due to a chemical reaction within the panel's encapsulation material caused by moisture and oxygen.


Hotspots occur when specific solar cells within a solar PV panel become overheated due to localized shading, dirt, or manufacturing defects.

Shading & Shadowing

Even partial shading on a single solar cell can cause a significant reduction in the energy production of the entire PV panel.


 Tiny cracks in solar cells can form from mechanical stress during installation and transportation or from environmental factors.


It can happen from moisture entering the backsheet and lead to a reduction in the panel's efficiency.

Potential Induced Degradation

This phenomenon occurs due to the high voltage potential difference between the solar PV cells and the frame, glass, or mount.

Solar Panel Diode Failure

Short-circuited bypass diodes can decrease energy output and create hotspots.

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Solar Panel Snail Trails

Snail trails are a type of defect that appears as dark or discolored patterns on the surface of solar panels and can be seen with the naked eye. They are caused by a chemical reaction within the panel's encapsulation material caused by moisture and oxygen. Over time, this reaction can lead to the formation of conductive pathways, reducing the panel's overall efficiency.

To spot snail trails, inspect the surface of the panels regularly for any visible dark streaks or solar panel discoloration. Snail trails are more noticeable under certain lighting conditions, such as direct sunlight.

There is no practical way to repair snail trails, but they do not necessarily always impact solar panel performance. If the panels are under warranty, you may contact the manufacturer for a potential replacement or determine if the snail trails impact solar electricity output.

Hotspots on Solar Panels

Hotspots occur when specific cells within a solar panel become overheated due to localized shading, dirt, or manufacturing defects. These hotspots can lead to irreversible damage to the affected cells and reduce the overall output of the panel.

To identify hotspots, use thermal imaging during the day when the panels are under full sunlight. Hotspots will appear as areas with significantly higher temperatures than the rest of the panel.

Ensure that the panels are not shaded by nearby objects or covered with dirt or debris. Therefore, it can be helpful to clean solar panels regularly in certain climates or locations impacted by debris. If a malfunctioning cell is causing the hotspot, consider replacing the affected panel.

Shading And Shadowing

Shading and shadowing are common issues that can severely impact solar panel performance. Even partial shading on a single cell can cause a significant reduction in the energy output of the entire panel.

Inspect the panels periodically during the day to spot shading and shadowing issues, especially when the sun is at a low angle. Look for objects, nearby structures, or vegetation casting shadows on the panels. Homeowners and business owners can monitor this as they’re around the panels more frequently; make sure they know to call their installer if they notice excessive shading or shadowing. Additionally, analyze the system's monitoring data for any unusual drops in energy production.

To address shading problems, consider advising trimming or removing nearby trees or objects that cause shading. Alternatively, you can use microinverters or power optimizers that mitigate the impact of partial shading on the entire system.

Solar Panel Microcracks

Microcracks, also known as microfractures, are tiny cracks in photovoltaic cells. This type of solar degradation is often caused by mechanical stress during installation, transportation, or environmental factors like temperature fluctuations. These microcracks can cause reduced panel performance.

To spot microcracks, visually inspect the panel's surface under proper lighting – cracks may appear as faint lines on the cells or the surrounding material. Also, you can use electroluminescence crack detection (ELCD) testing, a method that identifies microcracks that may not be detected from a visual inspection.

If the microfractures are minor and do not significantly affect the panel's performance, they can be left as is. However, it's best to contact the module manufacturer for possible warranty claims if they are severe and impact output. Otherwise, consider replacing the affected panel to maintain the system's overall efficiency.

Solar Panel Delamination

Delamination in PV panels is a serious issue that occurs when the layers of materials within the PV module separate or become detached. It can happen due to moisture entering the backsheet via cracks and can lead to a reduction in the panel's efficiency and busbar corrosion.

To identify solar panel delamination, conduct a thorough visual inspection of the solar panels. Look for any signs of bubbles, blisters, or separations between the layers of the panel, or discoloration or dark spots on the panel's surface. Also, electroluminescence (EL) testing can reveal delamination, by capturing images of the panel in the dark.

To address delamination when the solar panels are still under warranty, contact the manufacturer to report the issue. Solar panel delamination is often covered under standard warranties, and the manufacturer may provide replacement solar modules. If the delamination is severe and negatively affecting the panel's performance, it's best to replace the affected panels with new ones to ensure optimal energy production. However, beware that lamination can increase the likelihood of electrical shock, potentially creating a safety issue. If the solar system is reaching the end of its lifespan, it might be better to decommission it instead of replacing faulty panels.

Potential Induced Degradation (PID)

Potential Induced Degradation (PID) is a phenomenon that affects the performance of solar panels due to a high voltage potential difference between the solar cells and the frame, glass, or mount. This potential difference can lead to a degradation of the solar cells, resulting in reduced energy output.

To spot PID, monitor the solar panel's performance regularly and look for signs of decreased efficiency. Some symptoms of PID include a rapid decline in energy production or a significant drop in performance during high humidity and high-temperature conditions.

To address PID in solar panels, consider using PID reversal equipment. Properly grounding the system and using string inverters or module-level power electronics can also help mitigate PID effects.

Solar Panel Diode Failure

Diodes in solar panels are essential components that prevent reverse current flow. Short-circuited bypass diodes result in a power loss of 33% or greater and can create hotspots.

To spot diode failure, regularly monitor the system's performance and look for any significant drops in energy production or unusual patterns in the monitoring data. Additionally, inspect the panels for any visible signs of damage or solar panel discoloration.

Diode failure can be addressed by replacing the faulty diodes. Early detection and prompt replacement can help prevent further damage and ensure the optimal performance of the solar installation.

What are some of the most common solar panel defects?

Common solar panel defects include microcracks, where small fractures in the cells can develop during manufacturing or transportation, potentially reducing efficiency. Delamination, the separation of layers within the panel, may lead to moisture ingress and performance degradation. Hotspots, caused by shading or manufacturing issues, can result in localized overheating and reduced solar panel efficiency.

What causes solar panel discoloration?

Solar panel discoloration can be identified by observing variations in color or shading across the surface of the panels during routine visual inspection. PV module discoloration can be caused by various factors, including:

  • Exposure to UV Radiation: Over time, prolonged exposure to sunlight can cause degradation of the materials used in solar panels, leading to discoloration. This degradation can affect the appearance of the panels and reduce their efficiency.

  • Environmental Pollution: Airborne pollutants such as dirt, dust, pollen, and industrial emissions can accumulate on the surface of solar panels, leading to discoloration. These pollutants may create a film that reduces the amount of sunlight reaching the solar cells.

  • Moisture and Humidity: High levels of moisture or humidity, particularly in areas with frequent rain or fog, can contribute to the growth of mold, algae, or lichen on the surface of solar panels. This growth can cause discoloration and reduce the panels' performance.

  • Improper Maintenance: Lack of regular cleaning and maintenance can allow dirt, debris, and other contaminants to accumulate on the surface of solar panels, leading to discoloration over time.

  • Material Degradation: Certain materials used in solar panels, such as polymers and encapsulants, may degrade or yellow over time due to exposure to sunlight and environmental conditions, resulting in discoloration.

Is solar panel discoloration caused by defects?

Solar panel discoloration is typically the result of long-term exposure to the elements, such as sunlight, rain, and dust. Also, an uncontrolled chemical reaction between the lamination materials, such as EVA (ethylene-vinyl acetate), and the oxygen in the environment can contribute to discoloration. However, although solar panel discoloration may affect the aesthetic appearance of the panels, it does not generally impact their solar energy output or efficiency.

In some cases, severe discoloration could potentially indicate damage, although the presence of discoloration does not necessarily imply a solar panel defect. The most common defects in solar panels include issues such as hot spots, snail trails, and imperfections in the materials. These defects can impact the performance, longevity, and safety of the solar panels.

What causes solar panel diode failure?

Solar panel diode failure may occur due to overheating in high temperatures, excess voltage from mismatched panels, reverse polarity from wiring issues, manufacturing defects, lightning strikes, moisture issues causing corrosion, and natural aging. These factors can compromise the integrity of the solar panel diode, decreasing solar system output. Regular monitoring and maintenance are essential to detect and address potential issues quickly.

How can I prevent solar panel diode failure?

To prevent solar panel diode failure, ensure proper module installation, use surge protection devices, conduct regular maintenance checks for damage and cleanliness, optimize panel placement to minimize shading, and source components from reputable manufacturers. Additionally, implement temperature management strategies and ensure effective sealing to prevent moisture ingress. These measures collectively enhance the reliability and lifespan of your solar panel system by preventing solar panel diode failure.

How can I detect common solar panel problems?

Regular solar system monitoring and inspection are essential to detect common solar panel problems or defects. Visually inspect panels for physical damage, use monitoring software to track renewable energy production, and check inverter readings for abnormalities. Solar technicians can analyze shading patterns and conduct electrical tests to identify wiring issues. Early detection and intervention of solar panel defects and issues help maintain optimal solar system performance.

Solar Panel Defects are Rare But Possible

It’s critical for solar energy systems to perform as expected to have profitable projects. If PV systems aren’t producing the anticipated solar electricity output, it’s essential for solar contractors to identify and mitigate issues. Depending on the defect and cause, they may be covered by module warranties. Understanding the issues will help you pinpoint problems and educate clients on how to resolve them.

Want to stay current on solar energy industry trends? Check out the GreenLancer blog!


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