The present paper analyzes the Italian energy system focusing on the possible energy, environmental, and economic effects that the utilization of individual heat pumps for winter heating can produce. To this aim, a model of the Italian energy system is developed by employing the tool EnergyPLAN in order to develop an hourly simulation of the system at country level. Different scenarios in terms of heat pumps penetration, ranging between 10% and 50%, are simulated and sensitivity analyses in terms of average coefficient of performance of heat pumps are performed. The increase of heat pumps generation shows a steadily decrease of fossil fuel consumption for buildings heating, as well as a reduction of carbon emissions. The utilization of heat pumps for buildings heating leads to an increase of 10 p.p. in the load factor of the combined cycle gas turbine thermal power plants. Furthermore, an optimal heat pumps penetration is determined, namely 20%, which minimizes the energy system costs, calculated as the sum of fuel cost and externalities savings.