Natural dust accumulation or soiling on the surfaces of PV modules in large-scale PV power plants has a significant effect on the overall performance of these power plants, especially those located in arid areas such Jordan. In this manuscript, the soiling induced effects are quantified and modeled. Experimental setups for three common types of PV modules are utilized to acquire the data used for the models. Projection of the performance and economic impacts on large scale PV plants is carried out to emphasize the necessity to consider the soiling effects during the planning phase. Optimization of PV cleaning schedules for the best return-on-investment, in addition to the importance of determining typical soiling rates for forecasting models in PV power plants under planning is presented as well.