This article presents the monitoring results of an existing large scale system that combines heat pumps with unglazed solar collectors (used for heat production or as heat source for the heat pumps). The system provides space heating and domestic hot water to a new housing complex ( 10,000 heated m2) in Geneva, Switzerland. Detailed monitoring of one of the blocks ( 1000 heated m2, 32 inhabitants) enables to characterise the behaviour of the system (building demand, control strategy, temperature levels) and to determine the energy flows as well as the performance of the system. The results show a very low space heating demand for Switzerland ( 20 kWh/m2/yr), and an unusually high domestic hot water consumption ( 50 kWh/m2/yr). The measured seasonal performance factor of the system, including backup electric heating and heat source circulation pump, is 2.9 for 2012 (average of 2.5 in winter and 4.4 in summer). This result can partly be explained by the high domestic hot water consumption, which implies a heat production at high temperature. This project is part of IEA SHC Task 44 “Solar and Heat Pump Systems”.