The growing need to integrate in the electricity grids highly variable and not easily predictable renewable energies poses serious problems to grid operators for load balancing, and in particular it requires the availability of an increasing share of particularly flexible generation reserves to cope with intermittency of wind and solar generation. Moreover, considering that the daily evolution of energy production from conventional plants is generally out of phase with respect to the energy demand, it is extremely important to have energy storage systems able to manage the difficult relationship between availability and demand in order to stabilize the frequency of the grid and ensure continuity of service. The pumped storage hydropower systems have the advantage of being able to perform this function more efficiently than other storage systems. In this paper the results of a research aimed at evaluating the additional storage capacity achievable in Italy, both through the construction of new reservoirs and the rehabilitation and full utilization of existing ones, including those for irrigation, drinking water, industrial and lamination purposes is presented.. Moreover, according to the latest developments and successful experimentations of sea water pumping systems, potential sites along the Italian shoreline have been identified as well.