This paper examines a pathway for small islands to replace fossil fuels by renewable sources, such as wind and solar, up to 100% to economically achieve energy security and satisfy The Paris Agreement to limit temperature rise as close as possible to 1.5 °C, in an economically beneficial manner. Using Jamaica, as an example, it is shown that the introduction of intermittent renewable energy to an island grid, which is electrically isolated, relying totally on itself for backup, causes serious frequency fluctuations and load shedding. Simulations show that a Battery Energy Storage System (BESS) using Li-ion batteries can be employed to economically overcome these problems. It is also noted that the cost of batteries with longer discharge capacity is on the decline and their use is expected to be become economical in about 10 years. Looking at the reported pathway to satisfy The Paris Agreement, a 2-phase pathway is suggested. In the Phase 1 (2020–2030) 30% integration of intermittent renewables with BESS backup can be implemented in a manner that is not economically burdensome whilst the remaining fossil fuel system can provide the firm energy needed. In Phase 2 (2030–2055), more renewables can be implemented, provided sufficient long term storage, including batteries, can be added to provide firm energy. By 2030 the cost of such storage is expected to fall resulting in increased deployment without a financial burden to the islands. Ideally, during the period 2020 to 2055, there should be no new additions of fossil fuel plants and retiring plants should be replaced by renewable energy plants; although an account is necessary for plants already in the planning and development stages. The leeway period of 2020–2030 should be used for the preparation and planning of adding up to 100% renewables in all sectors.