Photovoltaic systems are the most effective alternative renewable energy source for isolated areas. But PV output power is affected by environmental factors such as temperature and dust accumulation. Periodically cleaning of PV panels increase converted solar energy. Isolated areas in Egypt do not have a connection to the electricity grid due to the high cost of transmission lines extension. Using conventional sources is not practical, as they cause emission gases. Moreover, they are limited sources. Renewable sources become essential power suppliers for isolated areas, as they are clean and unlimited sources. This paper introduces an optimal sizing for a stand-alone hybrid energy system PV/Wind/Battery (PV+WT+BAT) considering the dust effect on PV with different cleaning scenarios at tilt angle 30, supplying electrical energy needs for an isolated area in Egypt (Shalateen city). The optimal sizing is obtained using HOMER software. The results show that the optimal solution is the (PV+WT+BAT) system with a weekly cleaning scenario with a net present cost (NPC) of 103M$ and a cost of energy (COE) 0.319$/kWh. When using only a PV source for supplying the system, the optimal system is also with a weekly cleaning scenario with 117M$ NPC and 0.363$/kWh COE.