In order to achieve energy autonomy in island systems, the heavy mobility sector is considering hydrogen in order to reduce its dependence on fossil fuels and its emissions. This paper shows that hydrogen could be integrated on Reunion Island to decarbonise a fleet of 100 buses and assesses the impacts of such an integration. Through a novel methodology for the sizing of hydrogen refueling stations, the modelled stations are integrated into the island's overall electricity network. Three scenarios on the number of stations to be installed are presented in order to analyse their impact. The results show a total need of 7.6 MW of electrolyser, 5.3 MW of compressor and 951 kgH2 of hydrogen storage distributed among the installed stations. Installing four stations on the island would imply higher storage needs. The choice between installing two or three stations can be made according to cost, regulations or footprint criteria.