PVSYST is a PC software package for simulation, sizing and data analysis of complete PV-systems, with a user-friendly graphic interface under Windows. It is oriented towards engineers, architects and researchers. With its numerous graphical outputs, immediately available on screen, printer or in documents, it is also a powerful tool for education. PVSYST 1.0 simulates grid-connected systems in great detail (stand-alone and other systems are foreseen in near future). It includes large libraries of meteorological and geographical data, as well as commercially available components. An important feature of PVSYST is the detailed treatment of near shading, with a CAO tool to construct the 3D representation of the PV system environment. Other graphical tools are proposed for visualising solar geometry, PV panel or field behaviour under partial shading, mismatch effects, planes of different orientations, and quick meteo yields on tilted planes. In version 2.0, a new part will allow importation of measured data and perform detailed comparisons with simulated values, which will be a powerful instrument for data analysis of real systems. This feature has been used to carry out validations of the simulation with seven well-measured systems, which gave very good results.