We are developing a PC software package for simulation, sizing and measurements analysing of complete PV-systems, with a graphic interface under Windows. This program accepts a great variety of meteorological input data formats. It treats in detail the main perturbating effects identified during the careful measurement of real systems: far shadings (horizon limit), near shadings (partial shadings of neighbouring objects), incidence angle modifier, thermal behaviour of PV-panels (one-diode model), wiring resistance and panel mismatches of the PV-field (with built-in graphical tools for establishing the involved parameters), dynamic models of the system components (inverters, batteries, etc ... ). Results are provided in on-line tables and graphics of a choice of more than 60 variables. Other useful tools are provided for engineers: graphics and tables of over 40 solar parameters (solar geometry, clear day model, IAM effects, ... ), and electrical behaviour of PV-panels (or fields) with dispersion of the cells/panels parameters, or partial shading on one cell.