One of the major challenges of designing heterogeneous reconfigurable systems is to obtain the maximum system performance with efficient utilization of the reconfigurable logic resources. To accomplish this, it is essential to perform design space exploration (DSE) at the early design stages. System-level simulation is used to estimate the performance of the system and to make early decisions of various design parameters in order to obtain an optimal system that satisfies the given constraints. Towards this goal, in this paper, we develop a model, which can assist designers at the system-level DSE stage to explore the utilization of the reconfigurable resources and evaluate the relative impact of certain design choices. A case study of a real application shows that the model can be used to explore various design parameters by evaluating the system performance for different application-to-architecture mappings.