Solar Panel Degradation: What's Normal and What's Not

Solar panels are an incredibly durable technology, designed to generate electricity for 25 years or more. However, like any outdoor equipment exposed to the elements, they experience a gradual decline in power output over time. This natural process is known as degradation. Understanding what constitutes normal degradation versus what signals an abnormal issue is crucial for maintaining your solar system's performance and ensuring its longevity.

Waaree 540Wp Mono-Perc vs Waaree 590Wp TOPCon Performance Warranty accounting for the annual degradation

What is Normal Solar Panel Degradation?

Normal degradation refers to the expected, gradual decrease in a solar panel's efficiency and power output due to natural wear and tear over its operational life. This is a predictable process that manufacturers account for in their performance warranties.

• The Science Behind It: Over time, exposure to environmental stressors like UV radiation, temperature fluctuations (thermal cycling), and humidity can subtly alter the materials within the solar cells and the protective encapsulation. This leads to a slight reduction in their ability to convert sunlight into electricity.

• Typical Degradation Rate: For most high-quality crystalline silicon solar panels (monocrystalline and polycrystalline), the industry standard for normal degradation is 0.5% to 1% per year after the first year.

  
  

  

  Solar Panel Degradation Comparison between TOPCon and Mono-Perc Panels

• First-Year Degradation: Panels often experience a slightly higher initial degradation in their first year (sometimes 1-3% or even up to 2-3% for some technologies) due to phenomena like Light-Induced Degradation (LID) and Light and Elevated Temperature-Induced Degradation (LeTID). These are initial adjustments as the panels are exposed to sunlight for the first time, and the rate stabilizes thereafter.

• Long-Term Output: This means a panel guaranteed to produce 100% at installation might produce around 99.5% after year one, roughly 95% after 10 years, and still around 80-88% of its original output after 25 years.

• Performance Warranties: Reputable manufacturers provide a linear performance warranty that guarantees a minimum power output over 25-30 years. For example, a common warranty might guarantee 90% output after 10 years and 80% output after 25 years. If your panels degrade faster than this guaranteed rate, you may be eligible for a warranty claim.

What Causes Abnormal Degradation (and What to Look For)?

While some degradation is normal, a faster-than-expected decline in performance or visible physical changes can indicate an abnormal issue requiring attention. These issues often stem from manufacturing defects, improper installation, or severe environmental stress.

Here are common causes and their signs:

1. Physical Damage

• Causes: Hail, falling debris (tree branches), accidental impact during installation or maintenance, extreme wind loads.

• Signs:

  • Cracked or Shattered Glass: Visible cracks on the front glass surface. This compromises protection and reduces light absorption.

  • Dented or Warped Frame: Damage to the aluminium frame, which provides structural integrity.

  • Micro-cracks: Tiny, hairline cracks within the solar cells themselves, often invisible to the naked eye but detectable with specialized equipment (e.g., Electroluminescence (EL) testing). These can lead to reduced power output and hot spots.

  • Delamination: Separation of the layers of the solar panel (e.g., the encapsulant separating from the glass or backsheet). This can appear as bubbles or cloudy areas and allows moisture ingress.

2. Electrical Issues

• Causes: Manufacturing defects, poor soldering, loose connections, faulty bypass diodes, improper grounding.

• Signs:

  • Sudden, Drastic Drop in Power Output: A significant and unexplained decrease in energy production, often affecting a whole string or the entire system. (Regular monitoring helps detect this).

  • Hot Spots: Localized areas on the panel that are significantly hotter than the rest, visible as dark spots or "burn marks" (especially with thermal imaging). These occur when a section of cells becomes resistive, consuming power rather than producing it, and can lead to permanent cell damage or fire hazards.

  • Fluctuating Power Output: Inconsistent energy production that goes up and down erratically, potentially indicating loose or intermittent connections.

  • Snail Trails: Thin, brownish, snail-like lines appearing under the glass. These are typically a chemical reaction related to moisture ingress and faulty cell materials, indicating cell damage and reduced efficiency.

  • Discoloration (Yellowing/Browning): The encapsulant (EVA or POE layer) turning yellow or brown due to UV exposure and heat. This reduces light transmission to the cells.

3. Environmental Stressors & Manufacturing Defects

• Causes:

  • Potential Induced Degradation (PID): Occurs when a high voltage difference between the solar cells and the grounded frame causes a leakage current, leading to power loss. Exacerbated by high temperatures and humidity.

  • Backsheet Failure: The protective back layer of the panel cracking or tearing due to UV exposure, poor material quality, or mechanical stress. This allows moisture to enter and corrode internal components.

  • Moisture Ingress/Corrosion: Water penetrating the panel (e.g., through delamination or backsheet cracks) leading to corrosion of electrical contacts and internal components.

  • Manufacturing Flaws: Inherent defects in cell quality, assembly, or sealing that accelerate degradation.

How to Identify and Address Abnormal Degradation

1. Monitor Your System Regularly: This is your first line of defense. Use your solar monitoring app or portal to track daily, weekly, and monthly energy production. A consistent drop beyond the expected degradation rate is a red flag.

2. Visual Inspections: Periodically , visually inspect your panels from the ground (and safely from the roof if possible). Look for any of the physical signs mentioned above (cracks, discolouration, delamination, burn marks).

3. Check Inverter & Wiring: Ensure your inverter is functioning correctly and not showing error codes. Inspect visible wiring for any damage or loose connections.

4. Professional Assessment: If you suspect abnormal degradation, or notice any of the severe signs, contact us to diagnose issues accurately.

5. Warranty Claims: If the degradation is abnormal and falls within the terms of your performance or product warranty, we can help you initiate a claim with the manufacturer for repair or replacement.

   
   

Conclusion

Solar panel degradation is a normal and expected part of their long operational life. High-quality panels are designed to withstand decades of outdoor exposure while maintaining a significant portion of their original output. However, being aware of the signs of abnormal degradation and proactively monitoring your system can help you identify and address issues early, ensuring your solar investment continues to perform optimally and deliver clean energy for years to come.