Geothermal energy is an increasingly attractive alternative to the use of fossil fuels. Considering the growing energy demands in buildings, efficient systems – such as Ground Source Heat Pumps (GSHPs) – can be exploited for heating and cooling purposes and to supply domestic hot water. In order to achieve the ambitious targets set by the European Directives, the economical aspect is becoming an important issue. Thus, the present paper carefully describes the economical feasibility of a low enthalpy-geothermal plant with GSHP and vertical heat exchangers, with specific regard to an existing residential building. An Italian case study is further investigated, focusing the attention on recent public incentives and supporting measures. The influence of energy and thermo-climatic parameters – i.e. Coefficient Of Performance (COP) for heat pumps, Heating Degree Days (HDDs), thermal needs and typology of heat distribution system – is taken into account. Furthermore, in order to better evaluate the payback time for a specific investment, some financial indicators are calculated, namely Cash Flow and Discounted Cash Flow.