The next six years will begin to see long-term growth for commercial energy storage, according to GTM Research, driven in part by the growth of solar photovoltaics. More than 720 MW of distributed energy storage will be deployed in the U.S. between 2014 and 2020, GTM forecasts, representing a 34 percent cumulative annual growth rate.Energy Storage is the missing link in overcoming the intermittent nature of renewable energies. Although many people believe that electricity cannot be stored effectively, there are, in fact, several large-scale storage installations already in operation, in particular in the United States. From large-scale pumped-hydro storage and compressed air energy storage to smaller technologies such as batteries, flywheels and electrochemical capacitors, energy storage is very much on the minds of engineers, traders, security analysts and policy makers across the country.Energy storage, and in this context electricity storage, is considered by many as a potential Holy Grail, which ideally could resolve grid integration challenges from aggressive renewable energy development. Energy storage reduces demand for costly peak load power and spinning reserves, as well as deferring the need for additions to transmission and distribution infrastructure. Reductions of greenhouse gas (GHG) emissions resulting from energy storage could also facilitate attainment of the objective for reducing GHG emissions to 1990 levels by 2020.