The production of desalinated water generates multiple environmental impacts of different kinds. One of the most harmful indirect environmental impacts is derived from energy consumption, especially when the sources of energy used have their origin in fossil fuels. In the production of electrical energy in isolated island systems without electric system interconnections (either with other islands or with continental grids) and with limited renewable energy resources, the predominance of fossil fuels is common in the generation of the electrical power required to meet the global needs of the island system. This paper aims to analyse the indirect environmental impact of the origin of the energy used to obtain desalinated water in Gran Canaria. The result shows the indirect environmental impact generated have representative ranges, reaching 1.46 kg of fossil fuels per m(3) of water desalinated in the worst case of 2015. This reflects the need to reduce the desalination water demands, improve the efficiency plants and promote the tandem "renewable energy-desalination", as proposed in it. This island can be considered a good example of an isolated island location situated in a temperate subtropical climate with severe water limitations, where production of this industrial resource is of extreme importance.