High Temperature – Aquifer Thermal Energy Storage (HT-ATES), enables the storage and retrieval of unused or wasted energy during periods of low or representatively high demand. It is presenting a sustainable solution for the currently decarbonizing energy market. Vienna, being the largest city in Austria, has a lot of unused potential when it comes to energy that could be used to heat up water. Moreover, the city already has an established district heating network (DHN). Integrating this storage system within the DHN, would significantly decrease the carbon footprint as the current predominance lies on gas. This work contributes to the limited literature on HT-ATES experiences by presenting a reservoir model established using Modflow, a groundwater-simulating code capable of modelling aquifer systems. Utilizing the graphical user interface, ModelMuse, a simulation is created with varying input parameters. The resulting temperature profile reflects the behaviour of the system forming the foundation for the establishment of the recovery efficiency and the economic variables. Initially, the model was to set to a production rate of 3500 m3/day, a cut-off temperature (temperature at which the fluid is reinjected back to the reservoir) of 50°C and a reservoir thickness of 50m. During the simulation process, it was of interest to prove the importance of the constantly held thermal radius at 500m, in which the production rate was increased to 4000 m3/day. During this scenario, there no breakthrough was encountered, although the produced temperatures were lower compared to the initial production rate. Increasing the reservoir thickness to 75m boosted the recovery efficiency significantly. Even despite the increased thickness, the initial layout, intended for a volume of 3500 m3/day showed a higher recovery efficiency than a setup with 4000 m3/day. Although the recovery efficiency favours the lower production volume, it does not align with the results of the Levelized Cost of Heat (LCOH) or Net Present Value (NPV). These economic parameters directly benefit from the increase in energy output through the elevated production rate. The evaluation reveals promising outcomes, with the NVP yielding 3,23€ million and LCOH resulting at 55,17€/MWh.