A fuel cell-based energy storage system allows separation of power conversion and energy storage functions enabling each function to be individually optimized for performance, cost or other installation factors. This ability to separately optimize each element of an energy storage system can provide significant benefits for many applications. Various fuel cell/electrolyzer-based energy storage concepts and applications that employ these concepts using hydrogen as the energy storage medium are examined here. Technology and product development status of relevant PEM fuel cells, electrolyzers and complete regenerative fuel cell systems will be reviewed together with the status of various hydrogen storage technology options.