Methods, apparatus, and systems for power management of clustered computing platforms. Firmware provided on each platform is loaded for operating system runtime availability. The firmware traps power change events corresponding to a change in a power state of a component or device associated with a platform, such as a processor or a peripheral device. In response to the power change event, the firmware sends corresponding data to a power arbiter using an out-of-band (OOB) communication network/channel. The power arbiter determines an appropriate reallocation of power consumption allotments for the various platforms under its control based on a power management policy. Updated power consumption allocation information is then sent to selected platforms via the OOB network/channel. Upon receipt of the updated allotments, corresponding registers and/or tables are updated on the platforms to effectuate a change in power consumption of one or more components/devices associated with the platform.