The work focused on the analysis of the connection between a photovoltaic (PV) plant and an electrolyzer for hydrogen production. On the basis of PV-plant and electrolyzer experimental data, the effectiveness of the models adopted in the simulation program has been verified in order to choose the best model and, eventually, modify some parameters. By running the simulations, the procedure to optimize the PV-plant and the electrolyzer combination has been established. In fact, the simulation results might be considered to size an electrolyzer as small as possible, which is able to exploit up to the maximum power actually produced by the PV-plant during a working year. This criterion allows minimizing the overall plant costs. Furthermore, the possibility of deleting the maximum power point tracker and the dc/dc converter has been analyzed. On the basis of the obtained results, this opportunity is preferable to avoid the energy losses in the power control system; and it is convenient even from an economic point of view, considering that the electronic device costs are comparable with the PV-plant ones.