AbstractThe current paper summarizes the development of nano‐enhanced phase change materials (NPCMs) using capric acid (CA) and manganese dioxide (α‐MnO2) nanoparticles. The nanoparticles were obtained by the green synthesis technique using the leaves of Ficus retusa plant. The obtained nanoparticles were used in 1%, 2%, and 3% weight fractions in the nano‐formulations. The field‐emission scanning electron microscopy (FESEM) was employed to confirm the morphological structure and energy‐dispersive X‐ray (EDX) spectroscopy was used for the elemental analysis of the synthesized nanoparticles. The crystallographic studies were done using X‐ray diffraction (XRD) spectroscopy. The Fourier‐transform infrared (FT‐IR) spectroscopy results showed that the insertion of nanoparticles did not disturb the chemical configuration of CA. The differential scanning calorimetry (DSC) analysis revealed that the developed nanocomposites had excellent thermal energy storage capability that lay within the range of 145–164 kJ/kg. Five hundred extended thermal cycles were carried out which showed that the developed PCM had excellent thermal reliability and can be useful for a year‐long application. The variations reported with 1% nano‐formulation was −1.43% to +0.53%, −0.03% to +1.52%, and −6.67% to 9.94% with respect to onset, peak melting temperature, and latent heat of fusion. The thermal gravimetric analysis (TGA) results showed that developed PCMs were stable within the working temperature range. The melting/solidification curve showed faster heat storage and release rates owing to the increased thermal conductivity. These developed PCMs are useful for photovoltaic/thermal and building applications.