Photovoltaic (PV) technology is raising attention as a low-cost green energy source. It mainly finds applications in solar fields, on building facades and on rooftop. One of the main issues that can occur is the shading of solar cells inside the photovoltaic module which could affect the maximum power output of the PV panel and the lifetime of the cell itself. In order to predict the behaviour of PV panels in partial shading conditions, simulations and then measurements on two different photovoltaic modules have been carried out and compared. Data have shown that the maximum power output of the panels under 1sun illumination can be predicted by simulation with a 3% discrepancy from measured values, independently from the type of technology and interconnections of the PV module.