The output power generated by a PV module and its life span depend on many factors. Some of these factors include: the quality of PV type, solar radiation intensity, ambient temperature, shading effects, dust accumulation, weather conditions, geographical location etc. This paper reviews the major factors that significantly affect the performance of solar PV systems and discussed the distortion of I-V and P-V characteristics due to the effect of partial shading. Calculation of inter-row spacing between PV modules in case of 60 cells and 72 cells for minimizing shading effects by using Matlab program is presented. Dust effect study is performed on the output power of an installed system in Borj-El arab city during January and March and finally presents a comparison study between the same PV system installed in Borj-El arab city and Tiba city to report which is more efficient in energy production