Abstract The Canary Islands offer an example of an isolated electric grid of relative important size within the EU. Due to its peculiarities, the role of renewable energies and their complementarity with fossil fuels offers a solid path to achieving the main energy policy goals of the Islands. The purpose of this paper is to assess the current situation and the energy objectives proposed in the Energy Plan of the Canaries (PECAN, 2006) for the electricity industry, taking into account the average cost and the risk associated with the different alternatives for generating electricity by means of the Mean–Variance Portfolio Theory. Our analysis highlights the inefficiency of the current electricity generating mix in terms of cost, risk and lack of diversification. Shifting toward an efficient system would involve optimizing the use of endogenous energy sources and introducing natural gas to generate electricity. This scenario would mean reducing both cost and risk by almost 30% each, as well as atmospheric CO 2 emissions. Our results agree with the PECAN philosophy.