The heat source system is equipped with 3 boreholes with a total length of 120 m. The heating circuit is operated without buffer storage. The DHW circuit contains DHW storage. The system has a special feature, i.e. a second heat pump solely used for DHW production. Due to relatively high inlet temperatures of the second heat pump and the usage of underfloor heating with relatively low inlet temperatures, good preconditions for both heat pumps are provided.   

Its efficiency of 4.1 in 2010 is above the average of 3.9 of ground source heat pumps. The good values can be traced back to the low inlet temperatures of the heating circuit and the high inlet temperatures for the second heat pump. Both heat pumps have a share of 6 % of the total electrical energy demand and thus reflect the average of this type of system. The lack of a back-up heater positively influenes the SPF. The share of DHW in 2010 amounted to 13 % und lies significantly below the average of 18 % which also contributed to a good efficiency.