The Monte Caro/development distance method was then applied to the study of three solar hydrogen production routes: photoelectrochemical (PEC) and photocatalytic (PC) water splitting as well as photovoltaic + electrolysis (PV+E). For each, it was determined how much and which technological progress is needed to produce hydrogen at a cost level of 1.5-1.6 $/kg(H2) and the results were used to derive appropriate research targets.