The Canary Islands offer an example of an isolated electric grid of relatively important size within the EU. Generally, these systems do not have access to every technology available, nor can they be connected to continental grids when necessary. Due to their particularities, renewable energies, benefitting from their complementarity with fossil fuels, can play an important role in achieving the main energy policy goals of the islands. Electric vehicles (EVs), thanks to their storage capacity, can provide benefits to the power system reducing both the need for backup thermal generation and the amount of spilled renewable energy (mainly wind). Moreover, EVs can introduce more demand flexibility, which reduces the extra costs (intermittency costs) that renewable technologies impose on power systems. Comparing an efficient mix under a baseline scenario (null impact of electric vehicles) with an equivalent efficient mix under an alternative scenario assuming the introduction of a maximum of 122,000 cars into the Canarias market in 2025, we find a reduction of almost 11% in average generating cost (about 80 million euros/year), 9% in risk (measured as the standard deviation) and almost 13% in emissions.