The path to the mitigation of global climate change and global carbon dioxide emissions avoidance leads to the large-scale substitution of fossil fuels for the generation of electricity with renewable energy sources. The transition to renewables necessitates the development of large-scale energy storage systems that will satisfy the hourly demand of the consumers. This paper offers an overview of the energy storage systems that are available to assist with the transition to renewable energy. The systems are classified as mechanical (PHS, CAES, flywheels, springs), electromagnetic (capacitors, electric and magnetic fields), electrochemical (batteries, including flow batteries), hydrogen and thermal energy storage systems. Emphasis is placed on the magnitude of energy storage each system is able to achieve, the thermodynamic characteristics, the particular applications the systems are suitable for, the pertinent figures of merit and the energy dissipation during the charging and discharging of the systems.