Currently, refineries represent the largest hydrogen consumers in the world. Hydrogen is adopted in the hydrotreating and hydrocracking processes, which are crucial for removing sulphur compounds from hydrocarbons and producing lighter liquid fuels. Refineries mainly rely on fossil-based hydrogen, which is produced from steam methane reforming (SMR) or naphtha reforming. These production routes ensure low-cost hydrogen, but they result in significant CO2 emissions. The adoption of green hydrogen (produced through electrolysis) can thus represent a promising solution since it can enable a massive decarbonization without compromising the refining processes. This work considered as a case study an oil-refining plant located in northern Italy.