Not too long ago, D-Link announced the "industry's first Green Ethernet technology" with a new series of environmentally-friendly Gigabit switches, which reportedly "decrease energy costs by reducing power consumption without sacrificing operational performance and functionality." Apparently, these intelligent devices "recognize when a port is active or inactive and adjusts its power accordingly," and they can also "analyze the cable's length" and only send out the necessary amount of juice.
Now, don't get too excited. A router already produces very little energy compared to say - your PS3 (even when it's off) - so you save pennies, but every little bit counts, right? Not to mention, if you make this buy and you currently do not have any "Green" items in your home, this will be the promising start to an all-Green home!