Aspects of a method and system for energy-efficiency-based packet classification are provided. In this regard, a network link for communicating a packet may be selected based, at least in part, on an amount of energy required to communicate the packet over the network link, and based, at least in part, on an energy efficiency class to which the packet is assigned. The energy efficiency class may be determined based on one or more fields of the packet, wherein the fields may comprise one or more of an Ethertype field, a type of service header of an IP datagram, and a field pre-pended or appended to a payload of the packet. In this regard, during or subsequent to generation of the packet, the packet may be marked such that a network path traversed by the generated packet may be determined based on the energy required to communicate the packet over the network path.