Most energy management systems for hybrid electric vehicles still use rule-based energy management systems that rely on information stored in lookup tables, to define the current mode of operation and set-points for the low-level control laws. Because of the high number of parameters, the calibration of such energy managements can be a cumbersome task for the engineers. Mathematical tools are therefore inalienable to the calibration process. In this paper, it will be demonstrated, how the theory of hybrid optimal control can be used to calculate an initial parameter set for the energy management of charge-sustaining hybrids. The calculation procedure includes the solution of a hybrid optimal control problem to determine the controls for the optimal operation of the vehicle over a given cycle. The results can then be used to automatically calculate lookup-tables for optimal gear shifts, optimal torque-split between motor/generator and internal combustion engine and the determination of the drive mode (electric or hybrid mode).