Mafate is a natural protected cirque in Reunion Island, where about 300 dwellings are settled. The locals suffer from a massive energy insecurity because Mafate is not connected to the main grid. Although stand-alone solar microgrid installations are the preferred solution, they cause significant costs. "Micro Réseau Mafate" is a research project funded mainly by the European Regional Development Fund aiming at proposing strategies for microgrid development. In this paper, an actual islanded microgrid in Mafate is under scrutiny. The objective of the study is to rightsize the actual microgrid design considering the actual energy demand and solar resource measured in-situ. A Levelized Cost of Energy analysis is carried out and energy demand increasing scenarios are considered.