The perfect district heating modelling approach in energy system models: insights from an expert survey

District heating (DH) networks based on renewable and excess heat sources are set to play a key role in the transition to a climate-neutral energy system. Model-based assessments analyse the role of DH in terms of demand, infrastructure, supply, costs, and the impact on the energy system. Various approaches are employed, ranging from simulation and optimisation of individual DH networks to large-scale energy system models (ESM) that consider multi-sector interdependencies, e.g. heat-electricity interactions via power-to-heat. While there are reviews of various aspects of ESM and of specific DH models, there is still a lack of insight into how DH is modelled in ESM that capture sector coupling across several regions, the EU or worldwide. This paper addresses this gap by investigating the modelling of DH in 13 large-scale, multi-sector ESM. The results demonstrate that some ESM model DH with a single grid per country, while others use several grids per model region. Additionally, the level of techno-economic detail varies: Some ESM cover over 16 DH generation technologies, others cover less than eight technologies. The DH demand is often given as an exogenous input parameter, whereas some ESM model it endogenously. While all models have distinct advantages, they also have shortcomings, indicating that there is room for improvement in modelling techniques to better capture the complexity of DH in large-scale, multi-sector ESM.