Reliability analysis has been considered as an important step in any system design process. a reliable electrical power system means that the system which having sufficient power to feed the load demand during a certain period or in other word, having small Loss of Load Probability (LOLP). LOLP is defined as an expected fraction of load not met by its needed power from electrical power system during its lifetime. Photovoltaic (PV) / Wind Energy System (WES) hybrid electric power system (PV/WES HEPS) differs considerably from the utility grid (UG) in their performance and operating characteristics. With the interconnection of PV/WES as a HEPS into the UG, the fluctuating nature of the energy produced by these systems have different effect on the overall system reliability than the energy produced by UG. Therefore, this paper presents a complete study from reliability point of view to determine the impact of interconnecting PV/WES HEPS into UG. Four different cases have been investigated. A comparative study between these four different cases have been carried out from reliability point of view. The overall system is divided into three subsystems, containing the UG, PV and WES. The generation capacity outage table has been built for each of these subsystems. These capacity outage tables of PV and WES are calculated and updated to incorporate their fluctuating energy production. This paper presents also a fuzzy logic technique to calculate and assess the reliability index for each case under study. The fuzzy logic has the following design parameters:- type-Sugeno, gauss membership functions, 144 linear terms for output membership functions.