The large-scale implementation of solar hydrogen production requires an optimal combination of photovoltaic systems with suitably-designed electrochemical cells, possibly avoiding power electronics for DC-DC conversion, to decrease costs. Here, a stable, solar-driven water splitting system is presented, obtained through the direct connection of a state-of-the-art proton exchange membrane (PEM) electrolyzer to a bifacial silicon heterojunction (SHJ) solar module of three cells in series with total area of 730 cm2. The bifaciality of the solar module has been optimized through modeling in terms of the number of cells, module height and inclination. During outdoor operation in the standard monofacial configuration, the system is able to produce 3.7 gr of H2 h−1m−2 with an irradiation of 1000 W m−2 and a solar-to-hydrogen efficiency (STH) of 11.55%. The same system operating in bifacial mode gives rise to a higher …