With depleting reserves of traditional fuels, there is a worldwide demand for alternative energy solutions. One of the most promising developing technologies is energy storage, as it provides the benefit of capturing available energy for use at a later time. This paper gives an overview of the numerous forms of energy storage technologies under investigation and development, with a focus on thermal energy storage through adsorption. The current materials tested for adsorption energy storage capabilities are presented together with their corresponding performances. The materials with the best thermal energy storage performance presented in the literature include hybrid adsorbents, adsorbents with salt impregnations, and adsorbents with alkaline additions, which provide energy densities of 226–309kWh/m3. Furthermore, the demonstrative projects and systems that currently use this technology are presented. Although thermal energy storage using adsorption processes is not currently economically viable, with continued material development and system optimization, this technology has the potential to become competitive in the near future.