What Can We Do in Bucharest? The Issues of Decarbonising Large District Heating Systems

District heating systems are central to Europe’s decarbonisation efforts and its 2050 climate-neutrality target. However, given the deep embedding of district heating in the socio-economic system and built environment, meeting policy targets at the local level gives rise to a range of technical, infrastructural and socio-economic challenges. This is due to the high complexity and multidimensionality of the process, as well as the scarcity of local resources (e.g. land, surface waters, waste heat, etc.). In Bucharest, Romania, the largest district heating system in the European Union, the process of decarbonisation represents a particularly complex challenge. The system is characterised by high technical wear, heavy dependence on natural gas, significant heat losses and complex governance structures. This paper presents a strategic planning exercise for aligning the Bucharest system with the Energy Efficiency Directive 2023/1791. Drawing on system data, investment modelling and local resource mapping from the LIFE22-CET-SET_HEAT project, it evaluates scenarios for 2028 and 2035 that shift generation from natural gas to renewable, waste heat and high-efficiency sources. Options include large-scale heat pumps, waste-to-energy, geothermal and solar heat. Heat demand profiles and electricity price dynamics are used to evaluate economic feasibility and operational flexibility. The findings show that technical decarbonisation is possible, but financial viability hinges on phased investments, regulatory reforms and access to EU funding. The study concludes with recommendations for staged implementation, coordinated governance and socio-economic measures to safeguard affordability and reliability.