A new set of climatic data for different kinds of calculations has been compiled for various Swiss localities. This includes the generation of new design reference year data sets with hourly values for e.g. building simulations. The procedure conforms to a set of new European standards describing the algorithms. One key element in this is the processing of solar radiation information, especially for the separation into direct and diffuse components. The most advanced methodology was used. Simulation examples for testing the data showed surprisingly high differences in the energy consumption results compared to the old data sets. Differences as high as +34% in cooling energy resulted for a realistic case. Analysis showed the main reason being the radiation data and especially the direct/diffuse split. This puts into perspective some controversies concerning model details.