Achieving climate neutrality in district heating: The impact of system temperature levels on the supply mix of EU-27 in 2050

District heating (DH) systems are a critical component of the EU's strategy to achieve climate neutrality in the heating sector by 2050. Lowering the system temperature levels in district heating systems is acknowledged as a key facilitator for integrating renewable energy sources, thereby advancing the decarbonisation of the DH sector. However, the impact of system temperature levels on a decarbonised pan-European level DH sector remains underexplored. This paper investigates the effect of system temperatures on the DH supply mix of EU-27 in 2050. Through an extensive scenario analysis, we show that reducing system temperature levels can reduce the levelized cost of heat generation by 20 %. We find that large-scale heat pumps and geothermal energy plants are key technologies, particularly effective in low-temperature DH systems. Conversely, wastewater heat pumps and biomass tend to be more favourable for high-temperature scenarios. Geothermal energy exhibits potential in low-temperature systems but faces barriers of high initial capital costs. The role of hydrogen is found to be marginal, and biomass's role is highly sensitive to its price. From a policy perspective, our analysis indicates that targeted investments and regulations are needed to accelerate the transition to low-temperature systems, enabling the incorporation of more sustainable technologies.