The product development process of hydraulic systems for construction machines is often supported by unidimensional simulations. They are used i.e. to define properties of new parts or to test system functions. More and more simulations are also used within the concept phase to define the best suited system layout for a certain purpose. But the usage of simulations in the concept phase is a difficult task. Because of the generally high number of different possible concepts and different customer usage profiles, the simulation effort is overwhelming without a proper process. Therefore, this paper shows an approach for a model based concept evaluation with respect to customer specific usage profiles. For this, a modular simulation model as well as downstream customer specific weighting procedure of the simulation results is used. The paper includes the general approach as well as its application on the hydraulic system of an excavator.