This Recommendation identifies the main needs and applications of stationary electrical energy storage for ICT sites such as back-up on different grid quality and cyclic use of renewable energy systems. It also provides possible selection criteria for the right choice for the end system. The topics considered are: - families of electrical energy storage such as batteries or super-capacitors; - technologies types and their main properties; - adaptation to requirements (functionalities@ technology availability@ electrical characteristics@ environmental adaptation@ maintenance type@ cost@ etc.); - national or regional rules and regulations. The Recommendation highlights the need for evaluation methods that are complementary to existing battery standards as they allows different time frames including shorter tests compared to common energy storage industry tests. This Recommendation introduces a series of Recommendations that cover energy storage technologies (battery@ super-capacitor@ etc.) applicable to stationary telecom/ICT equipment used in telecom networks@ data centres and CPE.