Solar energy has a large potential, therefore it is a dominating source over other resources ,However its intermittent nature demands an storages system along with collector in order to make it more reliable. Solar air heaters utilize the rock bed as their storage system. This stored energy in rock bed can be used for providing the continuous supply of thermal energy in the absence of sun and it can also be used in addition to the current supply. In order to design a packed bed energy storage system, the matter of concern is to maximize the heat transfer with minimum pressure drop or pumping power. The paper is aimed at investigating the behavior of rock bed solar energy storage system, which is used to deliver the heat energy to a room. i,e the load (to heat a room ) is supposed to be 250 KW and requirement  duration is 24 hours. The overall performance of such systems is influenced significantly by the temperature distribution in storage unit which is affected by the system parameters i.e. void fraction and equivalent diameter of the bed. In this paper the performance of a rock bed solar energy storage system has been predicted and analyzed. Evaluation of performance is based on temperature distribution, thermal energy stored, volumetric heat transfer coefficient, pressure drop characteristics and available energy stored in the bed, as a function of system and operating parameters.