The relative cost of renewable energy depends on whether the costs of pollution and greenhouse effects are included in other energy sources. The cost of wind power is coming down all the time, having dropped by a factor of 5 in real terms since the early 1980s, while the cost of energy from fossil fuels is expected to rise in real terms. Sequestration of CO2 at fossil fuelled power stations, as is being seriously proposed, will further increase the cost of fossil fuelled energy. As to the reliability of potable water supply, wind turbines are very reliable machines and, although wind speed does fluctuate, with optimum sizing of the desalination plant for a given site, electrical energy in excess of the desalination plant's requirements during times of high wind speed will be fed ashore into the electrical grid to be matched by the drawing of electrical energy from the grid during times of low wind speed. Such electrical energy exchange is seamless and is well established technology.