Considering environmental impact as constraint in energy planning and sustainable policy has gained in importance over the past two decades. Electricity is currently a key contributor to greenhouse gases emissions. These impacts are particularly significant in the case of remote islands due to the share of fossil fuel in electricity mix. This paper aims to first provide a clearer understanding of the electricity situation Madagascar and Reunion Island. Then a detailed evaluation of their environmental impacts through the Life Cycle Assessment (LCA) approach. The GWP of the electricity mix is respectively estimated for Madagascar and Reunion Island at 464 and 673 g CO2-eq/kWh. Scenario based on renewable energy sources development on these islands has been investigated to define a road map to 2050, for a greener and cleaner electricity generation. The analysis is conducted to help policymakers in defining a framework for gradually change the fossil fuel power plants from now to renewables in 2050