Energy storage is the storing of some form of energy that can be drawn upon at a later time to perform some useful operation.

The following outline is provided as an overview of and topical guide to energy storage:

History of energy storage

Main article: History of energy storage

General energy storage concepts

1. Using a high density magnetic field. Energy ${\displaystyle E}$ in terms of magnetic field strength ${\displaystyle B}$ is

${\displaystyle E={\frac {1}{2}}B^{2}={\frac {1}{2}}Li^{2}}$

where ${\displaystyle L}$ is the inductance of the electromagnet and ${\displaystyle i}$ is the current.