The main objective of the this study is to determine the optimum size of systems able to fulfill the requirements of remote sites located in Hajer Bani Hameed in the north of Oman, Masirah Island and Mothorah area in the south of Oman. The methodology applied provides a useful and simple approach for sizing and analyzing the hybrid systems using HOMER. The aim is to identify a configuration among a set of systems that meet the desired system reliability requirements with the lowest energy cost, taking into consideration the temperature effect on the PV performance. The results of the analysis are a list of feasible power supply systems, classified according to their net present cost. Actual hourly load data are taken from these sites and are used in the model, and the meteorological reading (wind speed, solar radiation and temperature) are used either from the same site or from nearby one. A comparison between the costs of electricity generated from renewable energy resources in these locations is done. Moreover, the effects of the temperature on the photovoltaic cells efficiency and energy cost are considered. The cost of energy was found 0.206 $/kWh, 0.361 $/kWh and 0.327 $/kWh for Masirah Island, Mothorah and Hajer Bani Hameed respectively.