A method for operating a hybrid drive system which includes ascertaining an overall cost function that takes into account the cost function, which is a function of the operating point, for minimizing an energy usage of the hybrid drive system, and that takes into account one or more partial cost functions, which are a function of the operating point, which are each assigned to a requested special function; determining an optimized operating point of the hybrid drive system corresponding to an optimization according to the ascertained overall cost function; operating of the hybrid drive system at the operating point; and executing of those of the requested special functions for which the determined operating point is within an operating range assigned to the respective special function.