In a computer system having a power supply, processor, and additional subcomponents that are powered by the power supply, a method for estimating the total power requirements of the system under a variety of operating modes and configurations. In an exemplary embodiment, information concerning power requirements for each subcomponent under its operating modes is stored within non-volatile memory within the subcomponents. This information is accessed by the processor during the boot sequence, and if the information is not available, substitute information is provided. The compiled information is tabulated to compute the estimated total power requirement of the current hardware configuration. A display of this information, along with configuration selection rules, enables the user to select alternative operating modes and configurations and to show the resulting estimated power requirements.