Wind power generation in electric power systems has continuously increased in the past years because of the huge technology advances. Unfortunately, the wind is an intermittent power source. This is why the need of storing the energy comes. Moreover, the price of the storage is quite high. This work aims to investigate the optimal amount of energy storage necessary to keep the energy output constant to feed the grid. To do so, a research in different kinds of storage technologies is made. Then, the best one due to their cost, lifetime, efficiency, energy density and some special requirements is selected. After that, four places all over Spain are selected and their wind profile is evaluated. In this evaluation the amount of days in which there is not enough wind or there is too much wind are counted. Also the average wind speed during this time is calculated. After that, a specific wind power model is selected and some calculations are done. Then the average power output and the needed capacity storage are estimated. Finally, after selecting an appropriate storage model, the results are obtained and presented.