While heat pump systems combined with district heating could reduce the CO2 emissions of Geneva's heating sector, it is crucial to know and control their performance in real condition of use. This paper concerns detailed monitoring (hourly data, entire year) of a new low energy multifamily buildings complex, with centralized heat pump on wastewater (200 kW) and complementary gas boiler (600 kW). Heat production is covered at 45% by the heat pump (SPF: 3.03), with 55% complement by the gas boiler (85% efficiency). At the level of the buildings, domestic hot water supply (39.5 kWh/m2) accounts for 59% of the demand, against 41% for space heating (27.3 kWh/m2). For space heating, the gap between measured and climate corrected design values can be explained by operation conditions which differ from the norm (indoor temperatures, window openings), but remains quite lower than benchmark values on the recent building stock. Domestic hot water supply is also above the normed value, but coherent with a benchmark on other buildings. Finally, we highlight some issues and recommendations for optimized system integration and control concerning this type of innovative solution.