Many modern cities aspire renewable energy self-sufficiency. On a basic level, this can be achieved by producing enough solar and wind power to cover annual electricity demand. On a more ambitious level, the renewable power supply should cover consumption during every hour of the year. This could be reached by storing the energy in a local storage system with sufficient capacity. The Hydraulic Hydro Storage System is a solution to this ambitious level of self-sufficiency. It relies primarily on local resources and has an efficiency of 80%.