Electricity storage technologies in buildings are evolving, mainly to reduce their environmental impact and to improve self-sufficiency of buildings that produce their own energy through Building-Integrated Photovoltaics (BIPV) installations. To maximize self-consumption – minimizing the import of grid electricity – photovoltaic (PV) systems can be coupled with a hydrogen storage system converting the electricity to hydrogen by electrolysis during the summer season – when the on-site production is higher – and employing it during the winter season with fuel cells. This study focuses on the sizing constraints of solar hydrogen systems at building-scale using an innovative research-centre that will be built in Fribourg (Switzerland). It presents four stories and a mix-usage (office spaces and research facilities areas) and multi-oriented PV installation in order to produce enough electricity to achieve at least 50% of electricity self-sufficiency ratio. Using the PV production, this study aims to optimise the sizing of a hydrogen storage system allowing to reach the required self-sufficiency ratio with the lowest environmental impact possible. Ultimately, the global energy and financial efficiency of the system will be analysed.