This work intends to present a method for efficient analysis of the phenomenon of degradation in photovoltaic cells in Saint Petersburg (Russia) and Algiers (Algeria). The data used contain weather parameters (T°, wind, solar radiation) for 10 years. The rates of degradation of Si- photovoltaic cells were obtained from the data. It was noted from the results of comparing various data that the main factor in the formation of the degradation process is the technology of manufacturing photovoltaic cells.