Energy Storage — Definition

Definition

Energy storage retains energy for use at another time, usually by converting it into a physical or chemical form and later releasing it. Batteries and pumped-storage hydropower use different mechanisms but can both help match supply with demand over time.

Storage is not an additional primary energy source, and charging and discharging incur losses. Its power rating describes how quickly energy can be delivered; its energy capacity describes how much can be delivered over a period.

A meaningful comparison also considers duration, efficiency, operating life, cost and the particular service required, rather than selecting a technology from one headline number.