Together with three other EU funded projects (SOTHERCO, MERITS and SAM.SSA) COMTES developed a set of Key Performance Indicators for Compact Thermal Energy Storage (STES) systems. These KPI’s enable a comparison of storage systems based on different technologies. The KPI’s are definded on three different levels: System level, module level and material level. Developers of CTES systems are invited to adopt the KPI calculation methods and use these in publications and discussions. This page contains several files related to the KPI description and calculation.