Power over Ethernet (PoE) Explained



Power over Ethernet (PoE) allows power to be carried over network cables. PoE devices are divided into two categories:

  • Power Sourcing Equipment (PSE) are devices that supply power over Ethernet cables. Examples are PoE Switches, PoE Network Cards, PoE Injectors, and PoE Fiber Media Converters.
  • Powered Devices (PD) are devices that receive power over Ethernet cables, like IP cameras, IP phones, small Ethernet switches, and wireless access points.


The standards for Power over Ethernet (PoE) define how power is sent using Ethernet cables, including handshaking for supported power levels. A common PoE standard is IEEE 802.3af. That allows up to 15 watts of power to be sent over an Ethernet cable, but updated versions greatly increase the available power as shown below.

Standard Also Known As Delivered by PSE (up to)
IEEE 802.3af-2003 PoE 15.4W
IEEE 802.3at-2009 PoE+ 25.5W
IEEE 802.3bt Type 3 PoE++ 60W
IEEE 802.3bt Type 4 PoE++ 100W


Leveraging PoE can have many advantages depending on the specific application. It can reduce the cost and clutter of additional power supplies for IP phones or sensors, and eliminate the hassle and expense of running separate power to remote locations like ceilings or walls. It can also provide backup power in case of a power outage, and enable centralized control and monitoring of the devices.