With the ratification of the IEEE Std. 802.3az-2010 Energy Efficient Ethernet (EEE) standard the energy savings mantra of the green movement dives deep into the underlying infrastructure of your datacenter networks. The new standard is intended to allow energy savings at the network silicon level by reducing power demand when there are periods of reduced link utilization.
The standard specifies a technique known as Low Power Idle which reduces the power consumption when a link isn't being used. Given the bursty nature of most Ethernet traffic, this can result in a considerable reduction in power usage; especially for high-performance technologies such as 10GbE (1GbE and 100MbE are also covered within the standard).
The technology is focused on energy utilization of the underlying silicon by allowing for a rapid state change so that it is unnecessary for the entire circuit to remain powered up at all times; switching from a low-powered state to the high-powered transmission state quickly enough that there is no noticeable impact on network performance while reducing the overall energy usage of EEE-based hardware. Curiously enough, when 10BaseT was introduced, it only used peak transmission power when it had data to send, but all later (and higher performing) standards operate in a full-time powered up mode.
While this is all very interesting to the networking guys, from a theoretical approach, it will be up to the hardware vendors to implement solutions that build on this basic technology. There have been vendors already shipping solutions prior to the ratified standards and early adopters will need to assure themselves that their equipment meets the final ratified model.
While this technology isn't going to drop show as a major change on the electric bill for a small company with a few large switches and router, in the high-density world of the datacenter this is another opportunity to shave overall power consumption.