IEEE has a task force working on a new Ethernet standard that may lead to 75 percent power savings. The final spec is expected in March 2010.
Take Ethernet. You probably hadn't thought twice about that gray Ethernet cable on the floor, but an IEEE task force has been staring at it for well over a year, trying to make the darn thing more efficient.
The goals of the IEEE 802.3az task force are pretty straightforward: define a mechanism to reduce power consumption during periods of low link utilization and a protocol to coordinate transitions to or from a lower level of power consumption. It'll work only on new hardware, of course, but that hardware should be fully backward-compatible.
Parsing through some of the publicly available documents yields an awful lot of complex circuit diagrams ... and a bit of interesting information. According to a presentation by Hossein Sedarat of semiconductor manufacturer Aquantia, "channel staggering" in combination with a few other technologies may lead to a 75% power savings. That's in 10GBase-T, a wicked fast form of Ethernet. But it's not unreasonable to guess that ordinary 100MB Ethernet could see similar savings.