The paper presents a method of modelling photovoltaic (PV) cells in the MATLAB & SIMULINK environment. A two-diode photovoltaic cell structure was developed, featuring series resistance. Measurements of a PV panel were carried out to determine the value of series resistance, open circuit voltage, and short-circuit current. The model suggested was used to operate the ST-STP020S-12/Cb panel with an actual input function (measurements of solar radiation power density of the south-east area of Poland in 2011). Simulation experiments were conducted of the system modelled to determine current changes, power changes, electric energy production, voltage-current characteristics, and to come up with results and draw final conclusions.