Power over Ethernet (PoE) Explained

Power over Ethernet (PoE) technology enables ordinary Ethernet network cables to function as power cords. In a PoE-enabled network, direct electrical current (DC) flows over the network cable together with normal Ethernet data traffic. Most PoE devices follow either IEEE standard 802.3af or 802.3at.

Power over Ethernet was designed for use with portable and wireless electronic equipment like Wi-Fi access points (APs), webcams, and VoIP phones.

 PoE allows network devices to be installed in ceilings or wall spaces where electric outlets are not within easy reach.

A technology unrelated to PoE, Ethernet over power lines enables ordinary electric power lines to act as long-distance Ethernet network links.

Why Most Home Networks Don't Use PoE

Because homes typically have many power outlets and relatively few Ethernet wall jacks, and many consumer gadgets use Wi-Fi connections instead of Ethernet, the applications of PoE for home networking are limited. Network vendors typically only include PoE support on their high-end and business-class routers and network switches for this reason.

DIY consumers can add PoE support to an Ethernet connection using a relatively small and cheap device called a PoE injector. These devices feature Ethernet ports (and a power adapter) that enables standard Ethernet cables with power.

What Kinds of Equipment Work with PoE?

The amount of power (in watts) that can be supplied over Ethernet is limited by the technology.

The exact threshold of power needed depends on the rated wattage of the PoE source and the power draw of the client devices. IEEE 802.3af, for example, guarantees only 12.95W of power on a given connection. Desktop PCs and laptops generally cannot operate over PoE due to their higher power needs (typically 15W and up), but portable devices like webcams that function at less than 10W can.

Business networks sometimes incorporate a PoE switch through which a group of webcams or similar devices operate.

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