The proposed analysis is applied to a small neighbourhood of 10 residential buildings located in Madrid (Spain). Inherent the SDHS operator perspective, the results reveal a significant improvement in the stabilization of the SDHS performance due to the heat pump (HP) integration where the solar field temperature never exceeds 80^oC, and the seasonal storage tank (SST) temperature stands at 85.4^oC. In addition, the share of solar energy stands above 86.1% with an efficiency of 73.9% for the SST, while the seasonal HP performance factor stands above 5.5 for all optimal scenarios. From the investor viewpoint, an energy price of 59.1 Euro/MWh can be achieved for the proposed system with a payback period of 26 years. Finally, from the policymaker perspective, along with the significant economic and sustainable improvement in the SDHS performance, a substantial environmental improvement of 82.5% is achieved when compared to the conventional boiler heating system. The proposed analysis reflects a great motivation for different stakeholders to propose this system as a path toward the 4GDH in the future district energy systems.