A Comparative Investigation of Long-Term Performance Degradation Factors of Photovoltaic Modules

The long-term performance of photovoltaic (PV) modules is strongly influenced by environmental and operational degradation factors, yet existing studies typically report these factors in isolation, for a single site, module type, or fault mechanism, which makes it difficult to compare degradation behavior across climates and technologies. This paper addresses that gap by systematically consolidating twenty-two field, indoor, and simulation-based studies (2020–2024) into a single comparative framework that links module age, climate, panel technology, and fault mechanism to measured power loss. Performance indicators, including solar rating, test location, module age, annual power output, and long-term losses, are extracted and tabulated for direct cross-study comparison, alongside solar degradation mechanisms such as potential-induced degradation (PID), light-induced degradation (LID), and thermal cycling, and environmental stressors such as temperature fluctuation, humidity, soiling, and UV exposure. Across the compiled dataset, the maximum reported power degradation is 3.1912 W per year and the minimum is 0.0225 W per year, and degradation severity is shown to increase consistently with module age, from minor surface-level defects in 4–5-year-old modules to critical structural and electrical failures beyond 20 years. Building on this synthesis, mitigation techniques reported in the literature, including enhanced MPPT algorithms, anti-soiling coatings, and scheduled cleaning, are compared to identify which strategies are best suited to specific climates and installation types. The findings support the case for localized performance evaluation and adaptive, climate-specific maintenance planning to improve the longevity and return on investment of PV systems.