Eleven heating systems that combine combistores with solar thermal collectors and heat pumps have been tested and evaluated as a whole by detailed measurements in the laboratory with the Concise Cycle Test (CCT). The tests gave important insights into the behavior and the performance of these heating systems under transient operating conditions. One of the core findings is that the hydraulics and control strategy have a big influence on the temperature level of the heat pump condenser – and therefore also on the exergetic performance and the performance factor of the systems.