A method for performing system power budgeting within an electronic device and an associated apparatus are provided. The method includes the steps of: utilizing a power consumption index generator positioned in a specific subsystem to generate a power consumption index corresponding to the specific subsystem, where the electronic device includes a plurality of subsystems, and the specific subsystem is one of the plurality of subsystems; and performing configuration adjustment on at least one portion of the electronic device according to the power consumption index corresponding to the specific subsystem.