This research aims to show the effect of both dust accumulation and shadows (as factors that affect the performance of the Photovoltaic (PV) systems) on the experimented 36 cells of polycrystalline solar panel, which investigate the effect in terms of voltage (V), current (I) and power (P). The results showed that the relation between dust and the power of the solar panel is a strong inverse relation, as the power of the panel decreases at a rate of (-0.4575) per gram of dust. The study also showed that the relation between (dust) and each of the current and voltage is a strong inverse relation, where (I) and (V) decrease at a rate of (-0.0268) and (-0.026) per gram of dust respectively. The study found that, in the case of shading only one cell of the solar panel, the solar panel recorded a decrease in (P) by a rate ranging between (51.97% - 55.46%), while when shading an entire column or an entire row of solar panel, the power of the panel found to be decrease by (99.30%) and (97.55%) respectively.