In California 1/2 of the electricity comes from power plants fired by natural gas. Large scale energy storage is going to be key in reducing this contribution from natural gas. A YouTube video put together by Physics Girl describes the various methods to store large scale energy. By large scale energy we are talking about storage power plants that can put out 100 megawatts or more for an extended time. One method that is particularly intriguing is Thermal Batteries. This could be relatively lower cost but is years away. There is a local (Sunnyvale CA) startup company Antora Energy that is working on this.