Buildings account for 39% of global GHG emissions. In any building, space cooling/heating consumes the maximum electricity. Recently, encapsulated phase change materials (PCMs)-based cool thermal energy storage (CTES) systems have gained huge attention due to its numerous advantages in meeting building space cooling demand. Energy is stored inside these capsules in the form of latent heat. Considering the relevance of PCM solidification in capsules, two novel correlations are proposed to determine the inward and outward solidification time of phase change material (PCM) inside/around a spherical capsule based on its thermal conductivity and thickness. Further, an experimental investigation is also performed to validate the correlation. The correlation agrees closely to the experiment with a maximum inaccuracy of around 6.6%. Thereafter, a parametric analysis is also carried out to analyse the impact of both the parameters on inward solidification time of PCM. The results showed a significant reduction in solidification time up to a capsule thermal conductivity value of 0.3 W/mK. Beyond 10 W/mK thermal conductivity, capsule thickness did not affect solidification. The incorporation of these correlations into software will benefit engineers working in the fields of CTES, refrigeration, food processing, and plastics industries.