Compared to shallow geothermal systems, coaxial medium-deep and deep borehole heat exchangers (MDBHE and DBHE) offer higher temperatures and heat extraction rates while requiring less surface area, making them attractive options for sustainable heat supply in combination with ground-source heat pumps (GSHP). However, existing simulation tools for such systems are often limited in computational efficiency or open-source availability. To address this gap, we propose a rapid modeling approach using the open-source Python package “pygfunction” (v2.3.0). Its workflow was adjusted to accept the fluid inlet temperature as input. The effective undisturbed ground temperature and ground thermophysical properties were weight-averaged considering stratified ground layers. Validation of the approach was conducted by comparing simulation results with 12 references, including established models and experimental data. The proposed method enables fast estimation of fluid temperatures and heat extraction rates for single boreholes and small-scale bore fields in both homogeneous and heterogeneous geological conditions at depths of 700–3000 m, thus supporting rapid assessments of the coefficient of performance (COP) of GSHP. The approach systematically underestimates fluid outlet temperatures by up to 2–3 °C, resulting in a maximum underestimation of COP of 4%. Under significant groundwater flow or extreme geothermal gradients, these errors may increase to 4 °C and 6%, respectively. Based on the available data, these discrepancies may result in errors in GSHP electric power estimation of approximately ±10%. The method offers practical value for GSHP performance evaluation, geothermal potential mapping, and district heating network planning, supporting geologists, engineers, planners, and decision-makers.

District heating can increase the utilization of waste heat, but seasonal mismatch, network temperature requirements, and storage costs often limit useful recovery. This study assesses the integration of recovered heat from the Bolzano municipal waste-to-energy plant into the district heating system through direct use, tank thermal energy storage, and medium-deep borehole thermal energy storage coupled with a central heat pump. The analysis combines hourly dispatch modeling, coaxial borefield simulation, heat pump performance modeling, 25-year thermal assessment, and discounted techno-economic analysis for current and reduced-temperature network operation. After direct use and tank storage, 36.3 GWhth/year of surplus heat remains available for seasonal charging. Under current network temperatures, the feasible reference design uses 72 boreholes of 1,000 m depth and a 5.1 MWel heat pump, delivering 52.3 GWhth/year and covering 27.5% of residual demand while satisfying the 25-year ground loop temperature constraint. Reducing the network temperature to 70/40 °C increases the seasonal performance factor from 2.55 to 3.14 and lowers electricity use, but useful heat delivery decreases because heat pump capacity must be reduced to avoid excessive storage extraction. The base-case levelized cost of heat is 188.1 €/MWhth and remains nearly unchanged under reduced-temperature operation. Overall, the concept is technically feasible but economically constrained because high borefield capital costs are spread over modest useful heat delivery. The findings suggest that the concept is particularly relevant for dense district heating systems with stable waste heat availability, pronounced seasonal mismatch, suitable subsurface conditions, and favorable drilling, electricity, operating-cost, and financing conditions.