Solar Panel Efficiency Over Time

What Does “Efficiency Degradation” Mean?

Solar panels don’t stop producing power suddenly—they gradually lose efficiency. The term degradation rate refers to the percentage drop in a panel’s output year over year. According to NREL, a benchmark institute, the median degradation rate for modern crystalline silicon panels is around 0.5% per year. This means a panel retains about 90% of its initial output after 20 years.

Real-World Degradation Data

Several credible studies confirm modest declines in performance:

• A recent PV Magazine report states that degradation commonly averages 0.5% annually, allowing panels to operate for 25–30 years—though they may still produce usable power beyond that point
  
  
• The NREL PV Lifetime Project found that certain manufacturers (e.g., QCells and LONGi) maintain low degradation rates of 0.3%–0.4% per year; others like Jinko or Trina fall between 0.35%–0.55% per year, often concentrated in the first year.
  
  
• Some high-performing cases show panels retaining 80–85% of their capacity after 25 years—meaning a loss of only 0.5–0.8% per year.
  
  

Degradation in 25-Year Retrospect

Let’s break it down:

• Year 1: Expect a small drop of 1–3% due to light-induced degradation (LID).
  
  
• Years 2–25: Steady loss at ~0.3–0.5% annually.
  
  
• By Year 10: Your panel still performs at ~95–97%.
  
  
• By Year 20: Production is around 90–93%.
  
  
• By Year 25: Expect 85–90% of original output
  
  

Factors That Affect Longevity in Nova Scotia

Nova Scotia’s conditions—snow, salt air, wind, and freeze-thaw cycles—play a role in degradation:

• Salt-mist corrosion from coastal areas can stress materials. Panels certified for marine environments and robust racking help combat this.
  
  
• Seasonal temperature swings strain the glass and seals. Dual-glass or bifacial panels tend to withstand these cycles better.
  
  
• Snow, reflection, and albedo can be a double benefit. Bifacial panels in snowy regions often record 10–20% higher winter output, partially offsetting losses.
  
  
• Soiling—dust, pollen, salt spray—can reduce performance, commonly by 3–4% annually in snow-rich areas, unless the system is periodically cleaned
  
  

Technology Differences Matter

• Monocrystalline panels: Degrade slowly (~0.3–0.5% per year).
  
  
• Thin-film (e.g., a-Si, CdTe): Higher initial degradation (up to 3–4%), then stabilize
  
  
• Bifacial panels: Often more durable thanks to dual-glass, sometimes outperforming mono variants under snow and coastal conditions 

Table: Efficiency Over 25 Years for a 10 kW System in Halifax

(Assuming initial annual yield of 12,000 kWh)

Tips to Maximize Long-Term Performance

• Choose panels with ≥25-year performance warranties at 80–85% power output.
  
  
• Prioritize salt-mist resistance and sturdy racking—especially for coastal homes.
  
  
• Promote optimal orientation and tilt, enabling efficient snow shedding and reduced shading.
  
  
• Use inverter-based system monitoring to catch output drops early.
  
  
• Schedule gentle professional cleanings, especially after storms.
  
  
• Consider bifacial modules to harness snow reflectance and extend seasonal productivity.
  
  

Related reads: Bifacial Panels for Nova Scotia, Troubleshooting Solar Panels, Payback Period Guide

Final Takeaway

Understanding solar panel efficiency over time is vital for planning a system that endures. While all panels degrade, high-quality crystalline silicon modules typically lose only 0.3–0.5% per year, maintaining meaningful output for decades. In Nova Scotia’s climate, smart technology and design choices help ensure your panels continue producing clean, cost-effective energy well into the future.