Electrical energy storage is currently enjoying a considerable resurgence of interest, aided both by advances in the systems technologies themselves and also by fundamental changes in electricity markets, allowing the benefits of storage to be move clearly identified. This article, which introduces a special feature on “electrical energy storage”, reviews the state of the art and developments into the next Century, existing and potential applications, market potential for utilities and users and the increasing attention from Government agencies, manufacturing industry and research organisations. It concludes that the forthcoming challenge is for the various systems to prove both their technical and their commercial viability.