The hybridization of hydrogen and solar energy technologies is an interesting option to satisfy power demands in locations that are isolated from the electric grid. The main advantage of the photovoltaic (PV)-H2 hybrid system is the possibility of power storage by means of an electrolyzer (EL) which transforms the electricity into hydrogen (H2). The work described here concerns a methodology to design PV-H2 hybrid systems that considers the weather data and the electrical variables of the components to perform energy balances and to assess the system in terms of the load requirements, the levels of energy stored and the resulting costs. Two electrolytic systems (water splitting and ethanol electrochemical reforming) were studied in an attempt to find a best trade-off between the size and voltages of ELs. Ethanol reduced the energy requirements of EL at the expense of reagent consumption and lower current density. The energy supplied by these systems costs 0.28 €/kWh (i.e., roughly the same as power prices paid by domestic customers in Spain), but they have the merit of being autonomous and hydrogen has the capacity for seasonal energy storage ‒ thus avoiding electrification constraints in off-grid locations and limitations of short-term electrical energy storages. Display omitted •A novel model for PV-electrolyzer direct coupling is presented, used and discussed.•Two systems (water splitting and ethanol electrochemical reforming) are compared.•The energy supplied costs roughly the same as power prices paid by grid customers.•The systems have the merit of autonomy and capacity for seasonal energy storage.