Aspects of a method and system for holistic energy management in Ethernet networks are provided. In this regard, based on activity in one or more nodes in a network, power consumption in the network may be controlled via computational capabilities of node(s) in the network and/or via a data communication rate between nodes in the network. Activity in a network node may be determined based on deep packet inspection of traffic transmitted/received by the node, inspection of data exchanged between subsystems in the node, a state of an operating system running in the node, data processed or waiting to be processed in the node, information exchanged between an energy management entity in the node and an energy management entity in one or more other nodes, computing tasks delegated to the node, and/or instructions transmitted along with a computing task delegated to the node.