In order to provide efficient thermal management for an electric vehicle, the development of the cooling and conditioning system has to start early on in the overall product development cycle. This means that the first simulation models have to make do with relatively few actual data, mostly based on concepts and design studies. Accordingly the possible results are mainly useable for early on feasibility assessments.With more data and more details available, these simulation models gradually evolve, until in the end the overall cooling system is modeled with a relatively high level of detail. This allows e.g. transient analysis of warm-up or cool-down runs, simulation of driving cycles, implementation and optimization of control strategies.Although this basic workflow is true both for ICE and electric vehicles, for the latter specific topics like battery thermal management and HVAC integration add to the overall complexity. Especially the electric battery with its strong temperature constraints and its complex internal structure normally requires several modeling steps with increasing levels of detail during the development process.We want to discuss:Which data is required for different complexity levels of EV cooling system models?Which conclusions can be drawn from the different models and how do they influence the overall development process?How can continuous evolution of one simulation model during the product development cycle contribute to stable workflows?