Thermal energy systems with phase change materials (PCMs) have been studied extensively within small scale experimental systems with different arrangements, which have not been scaled to the size that could be utilized. The aim of this paper is to design an experimental plan for studying the potential of PCM within real scale thermal storage with a volume of 367 litres. Previous research has shown that flow rate is one of the main parameters that impact the performance of the system and, since change in the size of the tank relates to changes in flow rate, an experimental study of a tank with the size similar to that of commercial tanks is necessary. Secondly, since multiple melting temperature PCMs will be used, the placement of PCM is focal. The chosen flow rates are 2, 6 and 10 l/min and three sets of placement – no PCM as a base scenario, 55 °C PCM at the top and as third, a placement of four melting temperature PCMs with the one with highest melting temperature at the top – 65, 55, 34, 24 °C. The main analysis parameters are collector efficiency, comparison of delivered solar energy to consumer (solar fraction), tank losses and additionally required energy to prepare water (auxiliary energy).