**Abstract**

The accumulation of dust on the surface of photovoltaic (PV) modules reduces the intensity of the light transmitted through the cover glass, and therefore, the amount of energy generated by the solar cells. This issue, known as soiling. Affects PV systems worldwide, causing power losses as high as 70% in the worst scenarios This chapter presents an electro-optical investigation of the dust accumulated on the PV panel in the study area of Agadir-Morocco, by using a MOSFET transistor as load to truck the IV and PV characteristics of SX330J. For this purpose, Experiments of soiling effects on the performances of a PV panel have been performed using dust collected from two sites in the region of Agadir, Morocco: Adrar (AD) and Halieutic-Parc (HP). The results suggest that measuring the optical transmittance of the soiling accumulated on a PV glass can give enough information to quantify the impact of soiling on the energy production.

**Keywords:** solar panel, characterization, dust effect, transmittance, IV characteristics
