One of the earliest and most accessible energy storage system types is battery storage, relying solely on electrochemical processes. Lithium-ion batteries, known for their prevalence in portable electronics and electric vehicles, represent just one type among a diverse range of chemistries, including lead-acid, nickel-cadmium, and sodium-sulfur.
Zakeri and Syri also report that the most cost-efficient energy storage systems are pumped hydro and compressed air energy systems for bulk energy storage, and flywheels for power quality and frequency regulation applications.
Most of the world's grid energy storage by capacity is in the form of pumped-storage hydroelectricity, which is covered in List of pumped-storage hydroelectric power stations. This article list plants using all other forms of energy storage.
Energy storage is an enabling technology for various applications such as power peak shaving, renewable energy utilization, enhanced building energy systems, and advanced transportation. Energy storage systems can be categorized according to application.
Many individual energy storage plants augment electrical grids by capturing excess electrical energy during periods of low demand and storing it in other forms until needed on an electrical grid. The energy is later converted back to its electrical form and returned to the grid as needed.
Lithium-ion batteries are the most widely used type of batteries in energy storage systems due to their decreasing cost over the years. As of 2024, the average cost for lithium-ion batteries has dropped significantly to R2,500 per kilowatt-hour (kWh), making energy storage systems more financially viable and accessible for businesses.