To use solar energy effectively and as a standalone source, the performance of thermal energy storage device is crucial. The quantity and quality of energy stored using these devices play an important role in the efficient operation of thermal engineering equipment in the area of Heating Ventilation and Air Conditioning (HVAC), Refrigeration and many other. The selection of storage system depends mainly on application considering quality of energy and cost of storage. Phase change materials (PCM) have played a vital role in the storage of thermal energy in various applications. Out of the various types of phase change materials, organic compounds have a distinct advantage of high latent heat per unit volume, high thermal conductivity, non-flammability and low cost compared to inorganic compounds. The present study compares the performance of two of the most commonly used phase change materials like Paraffin wax and Fatty acids which are organic. They are highly chemically stable, melt congruently and super-cooling does not pose as a significant problem. Moreover, they have been found to be compatible with various kinds of materials of common use. The various performance parameters like temperature variation during charging and discharging, heat absorbed and rejected and overall system efficiency are evaluated for these two materials and also for the combination of these two materials. From the experimental results it is concluded that fatty acids show better performance characteristics than paraffin wax under the same operating conditions. Combination of the two PCM does not give much advantage in terms of operating efficiency.