ABSTRACT Considering the development of new technologies in the electricity generation sector, such as solar photovoltaic energy, some studies are made necessary to obtain the best performance of these systems. This generation model consists of modules, which are exposed to adverse climatic conditions, they receive direct influence of the dirt, according to the environment from which they were installed, which directly influences the performance of the system since, due to the disposal of waste on the module, a smaller portion of the solar radiation can reach the photovoltaic cell effectively. The objective of this work is to determine the ideal time for cleaning photovoltaic panels, aiming at high system productivity, having as object of study the photovoltaic panels of the Federal University of Technology - Paraná (UTFPR) Campus Curitiba, installed in the Green Office (GO) and at Neoville´s headquarters. Within this objective, it was necessary to verify its merit indexes, parameters used to compare grid-connected photovoltaic systems. The study shows the importance of frequent cleaning of panels, especially when they are installed in urban areas and close to high traffic access roads.