This paper explores the integration of energy communities at the national level through a bottom-up approach, using a mixed-integer linear programming (MILP) model. The study models district energy systems with building-scale resolution, applying the Dantzig–Wolfe decomposition to reduce computational time. The methodology is framed within a renewable energy hub characterized by a high share of photovoltaic (PV) capacities. The model considers both investments and operations, optimizing the interconnection of renewable energy sources with consumers. The study applies the model to five typical Swiss districts and weather locations, revealing a heterogeneous PV potential across the country. Present electricity tariffs promote a maximal investment in PV panels, reaching an installed capacity of 67.2 GW and generating 80 TWh per year. However, this exceeds the optimal PV capacity forecast of 15.4 GW_peak at the national level. Coordinated investment between local and national actors is necessary to prevent unnecessary expenses and curtailment of local renewable electricity. The results highlight the need for effective price signals to coordinate the needs of the energy infrastructure with the interests of local stakeholders, ensuring a fair and efficient energy transition.This paper explores the integration of energy communities at the national level through a bottom-up approach, using a mixed-integer linear programming (MILP) model. The study models district energy systems with building-scale resolution, applying the Dantzig–Wolfe decomposition to reduce computational time. The methodology is framed within a renewable energy hub characterized by a high share of photovoltaic (PV) capacities. The model considers both investments and operations, optimizing the interconnection of renewable energy sources with consumers. The study applies the model to five typical Swiss districts and weather locations, revealing a heterogeneous PV potential across the country. Present electricity tariffs promote a maximal investment in PV panels, reaching an installed capacity of 67.2 GW and generating 80 TWh per year. However, this exceeds the optimal PV capacity forecast of 15.4 GW_peak at the national level. Coordinated investment between local and national actors is necessary to prevent unnecessary expenses and curtailment of local renewable electricity. The results highlight the need for effective price signals to coordinate the needs of the energy infrastructure with the interests of local stakeholders, ensuring a fair and efficient energy transition.