Bottom-up method to derive cost curves for space heating savings in residential buildings for all European countries

Space heating constitutes approximately a quarter of final energy consumption in the European Union. Aligned with the ambition of the European Green Deal for climate-neutrality by 2050, effective energy system modelling is crucial for shaping strategies. However, integrating energy efficiency within the building sector remains challenging due to limited methodologies and data on specific energy consumption, heated surfaces, and retrofit costs. This paper proposes a methodology that balances accuracy and implementation effort through clustering analysis and relies entirely on open data primarily from the Hotmaps project to compute country-specific cost curves for energy savings in building space heating for each of the EU-27 countries. The aim is to empower energy system modelers to better incorporate energy efficiency measures into scenarios, thus advancing strategies in line with the European Green Deal. Findings indicate that the retrofits considered – insulation of façade, roof, ground floor; windows replacement – can save 40–60 % of space heating energy demand in most countries but marginal costs range widely, from 2 to 180 Eurocents invested per kWh saved over the retrofit lifetime. Climate conditions and existing insulation levels significantly influence the cost-effectiveness of these retrofits. This research provides valuable insights for policymakers and stakeholders working towards climate-neutral objectives. • Bottom-up method derives heat savings cost curves for EU-27 building stock. • Clustering and dynamic building simulations used for cost curve generation. • Open data sources leveraged, enabling reproducibility and scalability. • Facade and roof insulation show high savings at low marginal costs. • Climate conditions and existing insulation levels impact cost-effectiveness.