Island territories, due to their specific energy context, are at the forefront of energy transition studies with the aim of achieving energy autonomy. This is the case of Reunion Island, where the electricity mix is currently 70% carbon-based and where imports provide 80% of the energy consumption. In this context, this article assesses the facilities to install in the medium and long term to progressively reduce energy imports. Several scenarios of installed power generation capacities are studied for 2030 and 2050, associated with two scenarios for electricity consumption. Simulations are performed according these scenarios in order to define the electricity mix and the investments in new batteries and in the electricity transmission network reinforcement. For 2030, results show that a reduction in consumption compared with the trend could enable reduce costs and environmental impacts. For 2050, investments in new electricity generation technologies are essential to meet the needs of a 100% electrified vehicle fleet. If the overall consumption does not follow an energy demand management plan, all the energy sources on the island will have to be exploited to their maximum. The energy transition will also require large storage facilities and little reinforcement in the current electricity high voltage network.