The objective of this study was to experimentally establish thermal energy storage (TES) performance using a technical grade paraffin wax as a phase change material (PCM) in a vertical concentric pipe-in-pipe latent heat storage system. The melting and solidification temperature range of the paraffin was found as 38 degrees C-43 degrees C and 36 degrees C-42 degrees C, respectively. These values were well in agreement with the values measured by differential scanning calorimetry (DSC) analysis. The inlet temperature and mass flow rate of the heat transfer fluid (HTF) were selected as experimental parameters. The radial and axial temperature distributions were determined during the heat charging and discharging processes of the PCM. The temporal temperature data showed that the relevant experimental parameters were more effective on the melting time than on the solidification time due to increased natural convection during the melting process. Furthermore, heat fraction during the charging and discharging processes of the PCM were established. Experimental results indicated that the heat charging fraction was affected by change in the relevant experimental parameters more during the heat charging than discharging processes of the PCM. Finally, it was concluded from the results that the investigated technical grade paraffin wax encapsulated in the annulus of the two vertical cylindrical pipes had good thermal energy storage performance and it is a suitable latent heat storage material for passive solar thermal energy storage applications.