This contribution proposes the study of an ‘On-Line’ UPS, where adaptations have been made to replace the initial batteries with supercapacitors. As the electrical behavior of supercapacitors is different from that one of lead-acid batteries, a power electronics interface has been developed as well as the global control that allow the correct working mode of the UPS, where minor changes have been made. The total system has been simulated, and then tested. Main results that are presented show a positive results, even if the constraints applied to the supercapacitors lead to a non-optimal use of such storage devices. The main conclusions are that even if supercapacitors cannot propose an autonomy as large as that one of batteries, such components are well dedicated for UPS application for short-term grid interruption, with a fast reconfiguration when the grid is back. However, their use in UPS needs specific developments to be able to take advantage of their high lifetime.