Seasonal heat storage has been recognised in the LIFE22-CET-SET_HEAT project as one of the technologies, which enable the energy transition and decarbonisation of the district heating (DH) systems through integration of renewable and waste heat sources. This paper examines the performance of the Pit Thermal Energy Storage (PTES) technology. It is based on a case study of the system in Opole (Poland), which is a large fossil-fuel-fired DH system with a 2nd generation heating network. Almost all PTES systems, which exist today, are directly integrated with a heat source. This work addresses the technical, environmental, and financial viability of a “lift-and-store hub” concept, in which an integrated heat pump is used for PTES charging and discharging. During charging, the heat pump lifts the temperature from the network level up to the storage level (e.g. 95oC at the HP outlet). Such a solution enables the integration of surplus heat from distributed renewable and waste heat sources into the system. Although there are currently no examples of using co-located large heat pumps for PTES charging from the DH network, in many projects, this option may be considered since it prevents the reduction of source capacity in summer, when demand in the network is low, and supports the coupling of the electricity and heat sectors. The study applied MATLAB modelling for assessment of three PTES configurations (100 000 m³; 259 000 m³; 498 000 m³) with associated different heat pump capacities (15, 30, and 60 MW). The results revealed that under current economic conditions, most charging was supplied by CHP units, with the heat pump playing a supplementary role during discharge and negligible role during charge. CO₂ emissions increased slightly in the larger storage cases due to additional fuel used for charging and some storage losses. Storage efficiencies were high (88–92 %) because of daily charge/discharge cycles rather than purely seasonal use. Overall, economic modelling showed negative NPVs without subsidies for all configurations, with PTES-only performing better than PTES + HP options due to limited heat pump utilisation. Under current Polish energy, fuel, and CO₂ prices (2024), the project is not economically viable without subsidies. Additional costs would in-crease heat tariffs unless offset by public support. Long-term profitability depends heavily on future CO₂ prices, energy price trajectories, and availability of grants/green financing.