This paper presents the experimental result and its analysis of high temperature energy storage using molten salt. A single-medium (HITEC) thermocline thermal storage tank was tested under two mass flow conditions. The high and low temperature of the storage tank were 500oC and 300oC, respectively. The temperature distribution along the vertical direction was compared with different mass flow conditions, and the high mass flow rate showed the enhanced thermal storage performance. The most important conclusion from this study is that the thermocline TES (thermal energy storage) showed a sufficient feasibility compared to conventional two-tank storage.