A method for optimizing the efficiency and/or the running performance of a fan, wherein, starting from component-specific or function-specific numerical detailed models, on the basis of at least one algorithm, a model reduction and thus data reduction (data refinement) to component-specific or function-specific behavior models takes place, wherein the reduced data of the behavior models are coupled or combined in a system simulation to form a system behavior model having input and output variables, and wherein the input variables and associated output variables of the fan from the system behavior model are provided to an optimizer for selection in order to achieve optimized control of the system depending on framework conditions.