Power over ethernet. It seems like a pretty simple subject. The same standard that governs all other ethernet connectivity, IEEE 802.3, allows for a pair of wires to be used to carry up to 25 watts of power on the same cable as you use for data. It’s a pretty smooth way to power something as long as you don’t need a lot of electricity.
Power over ethernet usually uses an injector like the one you see above to add power from a wall socket. Some advanced network switches also have the ability to put power on the line but the average home user won’t generally see those.
25 watts isn’t enough to power a computer or printer, so when would you use power over ethernet? There are two common scenarios:
In security and surveillance applications, PoE (as the knowledgeable folks call it) is used for cameras,because it means running fewer wires and that way every camera doesn’t need its own wall outlet.
In networking applications like creating a large wireless network, PoE is used for much the same reason. If you want to give wi-fi to a large number of people in an office, use access points. Often times these access points are mounted to a ceiling and using PoE means that it’s easier to get power to these points, because commercial codes for electrical power often mean costly plenum-rated cables and steel conduits.
Simply put, use PoE for any case where you’re running an ethernet cable anyway and you don’t want to run a power cable. Just be sure that the devices you’re using are designed for PoE use. Plugging a powered ethernet cable into a device that’s not designed to accept it could damage the device. There are passive PoE splitters that will allow you to use Ethernet cable to get the power to the device then safely split it off. In a case like that you would have to be sure that you can provide the right wattage to the device you’re powering, though, and that may be a little harder than you think.