<p>Phase change materials (PCMs) are widely recognized for their potential in thermal energy storage due to their high latent heat capacity and ability to function across a broad temperature range. This review presents a detailed and quantitative analysis of PCMs, covering their classification, thermophysical properties, thermal characterization, degradation behavior, and enhancement approaches. PCMs are generally grouped into organic, inorganic, and eutectic systems, each offering specific advantages along with certain limitations related to thermal stability, conductivity, and cycling performance. Thermal analysis using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) are investigated in order to study phase transition characteristics and stability limits. The generally reported latent heat values lie between 150 and 300&#xa0;kJ kg⁻¹, while repeated thermal cycling can reduce energy storage capacity by approximately 5–20%. Major challenges such as supercooling and phase segregation, particularly in inorganic PCMs, are also considered due to their impact on heat storage efficiency and long-term reliability. Recent developments in material design, including nano-additives, encapsulation methods, and composite structures, have improved thermal conductivity by about 20–80% and enhanced structural stability. Even with these advances, practical issues such as cost, scalability, and durability continue to limit widespread application. This review connects thermal analysis results with material performance, offering insights that support the development of more reliable and efficient PCM-based thermal energy storage systems. By integrating DSC-derived thermophysical characteristics with TGA-derived thermal degradation behavior, this review provides an engineering-oriented framework for application-specific PCM selection, thereby bridging the gap between thermal characterization and practical thermal energy storage system design.</p>