This article presents the experimental results of a novel energy storage system that combines CAES (Compressed Air Energy Storage) with PHES (Pumped Hydro Energy Storage) technologies. As a reference, we called this system PH-CAES. In this alternative solution two storage tanks, the first with compressed air and the second with water, are separated by a valve. When electric power is required, the valve is opened and water flows to a Pelton turbine, which is coupled to an electric generator. Water from the Pelton turbine is discharged into a third tank. To store energy and recover the initial state, water is pumped back. We built a prototype to assess the PH-CAES performance, with focus on the power generation system. Experimental conversion efficiency was 45%, whilst the rational efficiency remained close to 30%. We also presented a discussion based on the second law of thermodynamics to show that there is a compromise between tanks exergies that maximizes the system performance. We also provide an operating map of this PH-CAES system to assist authors on new studies about this novel technology. (C) 2018 Elsevier Ltd. All rights reserved.