As the photovoltaic (PV) panel installed capacity has significantly increased over the last years, it is interesting to investigate the phenomena that may cause adverse effects on the performance of the modules, such as soiling. This work is aimed at evaluating the impact of PV panel soiling in the performance of a solar power plant on a soccer stadium in the state of Minas Gerais, Brazil, as well as to characterize the dust physically and chemically. The PV power plant is composed of 5910 multicrystalline silicon PV modules. Two diametrically opposed groups of modules were chosen and their generation was analyzed for 43 days in the second half of winter, each group containing reference modules that were manually cleaned every five days. A rainfall occurred on day 23 and some modules were manually cleaned on day 30. The collected dust was characterized by X-ray diffraction and by X-ray fluorescence. The particle size distribution and the shape of the particles were also investigated. For the sets of PV modules and the testing period studied, soiling reduced peak power in approximately 13.7% in the dry period, and 6.5% in the period after a rainfall. The energy production was reduced in approximately 16.5% in the dry period and 8.0% in the period after a rainfall. The average particle size of the southwest oriented group (Group A) and the northeast oriented group (Group B) was 35.3 and 28.7 pm respectively, but this difference did not make a significant effect in the performance of the modules. The collected dust was composed mainly of quartz, hematite and calcite. These results reinforce the need of manually cleaning the PV modules in order to maintain a high generation performance.