The performance of PV systems is generally affected by the real weather conditions. In the desert climate, dust accumulation is one of the main concerns that may cause a significant deterioration of PV efficiency. In the present work, experimental investigations were carried out to understand the dust characteristics and its effect on the electrical performance of PV modules under Sharjah, UAE weather conditions. The morphology of the dust sample indicates that dust particles have different shapes and small sizes (1.61-38.40 mu m). The results of the indoor experiments reveal a linear relationship between the dust density and the normalized PV power with a drop of 1.7% per g/m(2). Dust accumulation is a function of the tilt angle and it increases by 37.63%, 14.11% and 10.95% with respect to the clean module for the 0 degrees, 25 degrees and 45 degrees tilted modules, respectively. Outdoor experiments showed that the soiling loss increased by 12.7% while the dust density increased by 5.44 g/m(2) for a period over 5 months. By comparing the results of indoor and outdoor experiments, it was concluded that the linear relationship is reliable and can be used to predict the soiling loss of PV systems in UAE and similar weathers conditions. (C) 2019 Elsevier Ltd. All rights reserved.