Coupling of silicon solar cells with an off-grid proton-exchange membrane (PEM) electrolyzer is the basis for photovoltaic + electrolysis (PV+E). Electrical power from the solar cells is fed to the electrolyzer to produce pure hydrogen from water (see Figure ). The plant model is based on the one reported by Yates et al. A process description can be found in SI Section 3.1 and input parameters in SI Section 6.3.