Power Over Ethernet (PoE)

Power over Ethernet (PoE) is a networking technology that allows a single Ethernet cable to carry both data and electrical power.

Figure 1 – Power over Ethernet supplying a VoIP phone

It is mainly used to power VoIP phones, IP cameras, wireless access points, and IoT devices, all through the same cable that provides their network connection.

Benefits of PoE in Networking

• Cost efficiency – no need to install electrical outlets next to each device.

• Simplified cabling – one cable for both power and data.

• Flexible placement – devices can be installed in areas without nearby power sources.

• Centralized management – administrators can reboot or control power directly from the switch.

IEEE 802.3af (PoE)

Introduced in 2003, this standard provides up to 15.4 watts of DC power per port from the Power Sourcing Equipment (PSE), with about 12.95 watts available at the Powered Device (PD) after cable loss. It is suitable for low-power equipment such as basic VoIP phones or small wireless access points.

IEEE 802.3at (PoE+)

Introduced in 2009, PoE+ increased the available power to 30 watts per port, with 25.5 watts reaching the PD. This improvement supports devices that require more energy, such as IP cameras with pan, tilt, and zoom (PTZ) functions.

IEEE 802.3bt (UPoE and UPoE+)

The most recent standard extends power delivery by using all four wire pairs of the Ethernet cable. In Type 3 (UPoE), it can supply up to 60 watts per port, which is suitable for video conferencing systems or larger wireless access points. In Type 4 (UPoE+), it delivers up to 100 watts per port, making it possible to power advanced devices such as interactive displays and high-consumption IoT systems.

Table 1 – Comparison of PoE Standards