The heating and cooling sector is vitally important for the transition to a low-carbon and sustainable energy system. Heating and cooling is responsible for half of all consumed final energy in Europe. The vast majority of the thermal demand is fulfilled by fossil fuels, most notably natural gas. Low carbon heat sources (e.g. geothermal, biomass, solar and waste-heat) need to be deployed and heat storage plays a pivotal role in this development. Storage provides the flexibility to manage the variations in supply and demand of heat at different scales, but especially the seasonal dips and peaks in heat demand. Underground Thermal Energy Storage (UTES) technologies need to be further developed and need to become an integral component in the future energy system infrastructure to meet variations in both the availability and demand of energy. In this report, we we shed light on the importance of analysing UTES systems with a holistic vision, since their integration within district heating network (DH) depends on a vast number of parameters. A long-term market strategy is important to guarantee that enough injectable heat is available throughout the lifespan of the project, and that the DH will be able to accept the extractable heat from the storage. Besides, different merit-order strategies and system integration (hydraulic connections and heat extraction modes) also affect the energy efficiency of the UTES system.