In Europe, the increasingly restricting environmental regulations push the residential building sector to replace pollutant fossil fuel boilers with more environmentally friendly technologies. Double service Air-to-Water-Heat-Pumps (AWHP) are suitable for this purpose as they can assure space heating (SH) and domestic hot water (DHW) generation while reducing CO2 emissions. However, AWHP performances are quite dependent of the commissioning and running processes. In this context, this document evaluates the potential impact of the commissioning phase for a double service AWHP in terms of electricity consumption, thermal comfort and energy bill. This evaluation is realized through the study of key parameters settings. The analysis builds upon an AWHP system model developed in the Modelica environment. The results of this work show that commissioning phase has an important influence on system performances. A parameterization adapted to the dwelling is needed in order to guarantee a good SPF (Seasonal Performance Factor), a correct operation as well as user’s comfort.