The rise in energy consumption in modern societies has been unprecedented in recent decades. Non-dispatchable renewable energies include all the generation sources which have intermittent and uncertain characteristics such as wind and solar photovoltaic energies. The incorporation of high levels of penetration of variable energy sources generates new costs for the rest of the electric system, creating discrepancies between costs with and without non-dispatchable renewable energies. A correct allocation of resources requires prices to reflect the real costs of generation. The aim of the wind-hydro project on the island of El Hierro (Canary Islands, Spain) is for the electricity consumption of the approximately 10,000 population to be met exclusively through renewable-sourced energies. The operating philosophy is based on satisfying demand with renewable energies while ensuring grid stability. The pumped-hydro system is designed to allow the transformation of non-dispatchable renewable wind energy into dispatchable renewable hydraulic energy. The wind-hydro plant of El Hierro is an example of the effects of the large-scale incorporation of non-dispatchable renewable energy in an isolated system, the installation of which has increased the real costs of the generation of electrical energy. (C) 2018 Elsevier Ltd. All rights reserved.