IEEE 802.3bt: Everything you need to know about Power-over-Ethernet

FEBRUARY, 2023


Power over Ethernet (PoE) is a standard that allows electrical power to be transmitted over standard Ethernet cables to power devices such as IP cameras, access points and IoT devices. It offers network installers to install network devices in locations without direct mains power. PoE offers plenty of advantages, from time savings to decrease the cost of installing new network hardware.


IEEE 802.3bt is the latest major iteration of the PoE standard, and its benefits and specifications are often misunderstood. Whether you are an engineer, an IT professional, or just someone interested in PoE technology, this article will provide you with a comprehensive understanding of the IEEE 802.3bt standard and its role in the connected world.


What is IEEE 802.3bt PoE?


The original PoE standard - 802.3af - was released by the Institute of Electrical and Electronic Engineers in 2003 to provide DC power to lightweight powered devices such as IP phones. However, as PoE adoption grew, the limitations of the standard became clear.


802.3af’s 15.4 W of DC power (minimum 44 V DC and 350 mA) quickly became a limiting factor - especially as only 12.95 W was left available after accounting for dissipation in the cable. In response, the IEEE launched the updated 802.3at standard in 2009, increasing the maximum PoE output to 30W of power. However, even that power output became insufficient after the explosion in the Internet of Things (IoT) devices increased the power demands on Ethernet networks.


The latest standard released by the IEEE is 802.3bt. There are two power classes specified in this standard:

  • Type 3/PoE++ : 60W max power, 51W to powered devices (PD) after cable loss
  • Type 4/High Power PoE: 90W max power, 71.3W at PD

The flexibility afforded by the increased power output has led to the widespread use of PoE technology in various applications, including building automation, industrial automation, and the aforementioned Internet of Things (IoT) devices.


What are some useful 802.3bt Applications?

Let’s discuss some interesting examples of 803.2bt in action!


Building Automation

Smart buildings or building automation refers to integrating a facility's systems into a single network that is centrally controlled using IP-based structured cabling.With an Ethernet network using the 803.2bt standard, all your Internet-enabled devices can be hooked up to your network and powered by the same cable. This removes the need to wire mains power to these components. The original PoE standard could power simple access control systems and alarms, but the increased power output of 802.3bt offers building managers a wider array of potential applications. This includes:

  • Smart access control systems:

    Ethernet networks can power Internet-enabled smart locks that can be centrally controlled by a building’s security. Whilst the locks themselves are fairly low-power and can be handled using an 802.3at power source, control systems like the Ubiquiti UniFi Access Hub IP Networked Door Controller can draw up to 40W.

  • IP Surveillance Cameras:

    PoE technology can be used to power security cameras, making it possible to install cameras in places where power outlets are not available. IP cameras with built-in heaters and PTZ motors can use the extra power headroom.

  • Wi-Fi access points:

    The ability to both power and connect WAPs using a single cable can simplify the process of extending your wireless network significantly. High-end Wi-Fi 7 APs like TP-Link EAP780 Tri-Band router can draw up to 60W, so the added power output headroom of 802.3bt is helpful here.

  • Smart LED lighting:

    Networked LED lighting systems can draw lots of power, and so the improved 71.3W PD power limit is helpful here too.

Internet of Things (IoT) Devices

The recent explosion in the Internet of Things (IoT) devices has opened some brilliant opportunities for new industrial applications.These industrial IoT devices are often complex, high-power equipment, and installing new power infrastructure to run them can be difficult and expensive. 802.3bt offers enough power to facilitate power-hungry IIoT devices, including:

  • Factory Automation:

    PoE technology can be used to power industrial automation devices, such as sensors, actuators, and control systems, making it easier to install and manage these devices.

  • Robotics:

    PoE technology can be used to power robotic devices, such as industrial robots, making it possible to install these devices in places where power outlets are not available.

  • Machine Vision Cameras:

    10 GigE Vision cameras in industrial settings such as manufacturing often need to be small and lightweight. High-speed cameras like the VRMagic Ric10 can draw up to 40W, and by using PoE, you can power flexible machine vision systems with only one cable.

Customer Touchpoints

By using Ethernet networks to power touchpoint devices, such as displays, POS systems and more, you can position these devices around where customers will use them the most - delivering better customer experiences. To deliver an omnichannel experience, you’ll need to connect these touchpoints to the Internet. Using PoE, you can install them anywhere and ensure you’ve got a reliable network connection too. With the 90W of output power, you can use 802.3bt in a variety of touchpoint applications, including:

  • Self-service kiosks
  • Digital signage
  • Computers
  • Video conferencing systems
  • POS
  • Televisions

Let’s take digital signage as an example. As displays grew larger and resolutions increased, the display industry ditched PoE as a power standard for displays - with Samsung discontinuing its only remaining PoE display. This is no surprise as 4K displays regularly see power outputs in excess of 802.3at’s 30W power limit - with Samsung’s QM43B 4K display having a typical power consumption of 70W - we expect to see more 4K PoE displays and touchscreens.


Final thoughts


Power-over-Ethernet offers system integrators far more flexibility in how they install and connect network devices. The 802.3bt standard offers a much higher maximum power output, unlocking interesting new applications for Internet-enabled devices. The benefits of removing the need to hook up devices to mains power cannot be understated. Installing power outlets is costly, especially if you’re adding plenty of devices to your network. Using PoE offers far more flexibility, as devices can be installed more quickly and their position can be far less permanent. All you’ll need to do is run some structured cabling and plug the device in!


We’ve just scratched the surface of what’s possible with IEEE 802.3bt PoE. As more businesses begin to reap the rewards of the technology - and as the IIOT sector continues to grow, we’re sure that the number of devices that support the standard will rise steadily.