Continental-scale assessment of typical meteorological years in a changing climate: metrics and insights from 5,000 European locations

• Built, validated and released TMY datasets for 5,000 European sites. • Compared TMY3 and ISO methods across 15- and 30-year baselines. • TMY3 outperforms TMY ISO across error metrics and HDD/CDD. • 30-year TMYs show higher statistical stability than 15-year sets. • 15-year TMYs better capture recent warming and cooling demand shifts. In this study, Typical Meteorological Year (TMY) datasets for more than 5,000 locations across Europe are constructed using the Copernicus European Regional ReAnalysis (CERRA) dataset. Two established TMY generation approaches, TMY3 and ISO 15927–4, are applied for both a conventional 30-year period (1991–2020) and a more recent 15-year period (2005–2020) to assess the influence of reference period length on dataset accuracy and representativeness. The methods are evaluated by comparing the TMYs produced with the reanalysis-based Actual Meteorological Year (AMY) data that they are based on using statistical error metrics, spatial autocorrelation and decompositions methods. This study provides the first continental-scale comparison of the TMY3 and ISO 15927–4 methods based on a common reanalysis dataset, quantifying the trade-offs between reference-period length and representativeness. Findings show that 30-year TMYs provide stronger statistical stability, while 15-year datasets may be better positioned to capture recent climatic warming. ISO-based TMYs emphasize temperature-driven performance metrics, whereas TMY3 offers a more balanced representation of both temperature and solar radiation. However, the largest variations across all indicators occur in Cooling Degree Days (CDD), highlighting that cooling energy estimates based on TMYs may be sensitive to methodological choices and reference period length. Together, the findings highlight important trade-offs between methodological choices and reference period length. The study provides an open-access repository of 20,108 TMY files to support building energy simulation, renewable energy assessment, and climate-responsive design across Europe.