Deposited particulate matter on the surfaces of PV modules decreases their electricity production by reducing the transmission of solar energy to the PV cells. PV module efficiency refers to the actual efficiency once installed and takes into account factors such as dirt (deposited ambiental particulate matter), climate, orientation, temperature, etc. The objective of this study was to experimentally estimate the loss of PV module efficiency due to deposited particulate matter. A normalized current-voltage (I-V) curve was done for eight monocrystalline silicon half-cell PV modules, exposed for 8, 13, and 24 months, under dirty conditions and after cleaning. In all cases, deposited particulate matter was collected for subsequent mass determination. The main preliminary results obtained were: linear dependence relationship, with a slope of 4.029 (%/(g/m2)) and R2 = 0.9673, between the loss of performance and the mass per unit area of deposited particulate matter on the PV module and for an average deposited mass of 0.4 g/m2 the performance of the PV modules studied is reduced by around 1.6% where, if the value of 19.85% of the manufacturer’s efficiency reference is taken as 100%, this means an 8.4% reduction in its generation due to contamination by deposited particulate matter. An increase in maximum power (Pm), short-circuit current (Isc) and open-circuit voltage (Voc) was observed in all cases after cleaning the PV modules.