What is Power over Ethernet: Different Types of PoE?

Power over Ethernet (PoE) has revolutionized the way we power network devices by simplifying connectivity. Imagine a single cable that delivers both data and electrical power—eliminating the hassle of separate power cords.

PoE is an efficient technology that is making it easier to deploy IP cameras, wireless access points, and VoIP phones in areas where power outlets might be scarce. But how exactly does it work, and what are the different types of PoE standards available today?

This guide will break it all down for you.

Power over Ethernet, commonly abbreviated as PoE, is a technology that allows electrical power and data to be transmitted simultaneously through an Ethernet cable.
Initially introduced by the IEEE to simplify network installations, PoE has made deploying devices in various environments—such as IP cameras in remote locations or access points in large facilities—more accessible and cost-effective.

PoE operates under the IEEE 802.3 standards, which define the different types of power delivery capabilities, including PoE (IEEE 802.3af), PoE+ (IEEE 802.3at), and PoE++ (IEEE 802.3bt).

Each of these standards supports different power levels to accommodate various devices, from low-power sensors to higher-power devices like LED lighting and smart TVs.

Power over Ethernet was first developed by Cisco in 2000 to enable scalable and manageable power delivery to Cisco IP-telephony handsets. The idea was inspired by traditional PSTN (public switched telephone network) landline phones, which deliver 48V DC power over copper cabling used for communications. PoE initially utilized the unused pairs of the four twisted pairs of copper wires found in typical Category 5 (Cat 5) cable.

In 1999, both the IEEE and the Ethernet Alliance began working on standardizing PoE to ensure interoperability across a broader range of powered devices and power sourcing equipment.

The first standard, IEEE 802.3af, was ratified in 2003, specifying that power could be carried by either spare pairs (pins 4 and 5 or pins 7 and 8) or data pairs (pins 1 and 2 or pins 3 and 6). This standard also included a mechanism to protect non-PoE devices by adding a 25-kΩ resistor between the power pairs on the powered device, ensuring power was supplied only if this resistive value was detected.

The value of PoE was quickly realized for reducing cabling needs, improving safety, and simplifying installation, which saved time and reduced costs. As demand grew for more powerful devices, subsequent standards were developed:

The use of PoE technology is growing at a rapid pace across many industries, including IT, security, and smart building solutions.

In fact, the global PoE market is projected to grow at a compound annual growth rate (CAGR) of 13.2% from 2022 to 2030, driven by the increased demand for IoT devices and smart infrastructures. Here are some key benefits of using PoE:

To fully understand PoE, it’s essential to distinguish between the different types:

Each type of PoE has specific characteristics that make it suitable for different applications. PoE (Type 1) is ideal for basic devices, while PoE+ (Type 2) can power more demanding devices like advanced wireless access points. PoE++ Types 3 and 4 are used for devices requiring even higher power levels, such as LED lighting and video conferencing systems.

Power over Ethernet is categorized into different classes based on the power requirements of the powered devices (PD) and the power delivered by the power sourcing equipment (PSE). The following table provides an overview of the PoE classes:

The following table provides a comparison of the different PoE standards, highlighting key properties such as power available, voltage range, and supported cable types:

The Institute of Electrical and Electronic Engineers (IEEE) released the first Power over Ethernet (PoE) standard in 2003, establishing common guidelines for the delivery of power over an Ethernet network.

PoE provided compelling benefits over conventional AC power, including easy installation, increased safety, reduced capital expenditures, and lower operating costs, paving the way for rapid adoption.

The following table provides an overview of the PoE standards, including types, classes, commonly known names, minimum power sourcing equipment (PSE) output power, and minimum power required at the powered device (PD):

Note: The difference between the power provided by the PSE and the power received by the PD is due to power lost in transmission in the form of heat.

There are several types of PoE devices, each serving a specific role in the PoE ecosystem:

These are any PoE-compliant devices that can be powered through their RJ45 network port. Examples include IP cameras, wireless access points, and VoIP phones. PDs are growing at an annual rate of 12%, driven by expanding applications in video conferencing, smart buildings, sensor networks, point of sale (PoS), and digital signage.

The maximum length of an Ethernet cable is 100 meters, but this can be extended using a PoE extender. Extenders repeat both data and power, effectively extending the cable run by another 100 meters. Ruggedized PoE extenders are available for industrial applications.

These devices are used to power non-PoE devices. A splitter draws power from the Ethernet cable and passes it to the device via its power port.

Also known as midspans, injectors add power to an Ethernet cable, allowing non-PoE networks to support PoE devices. This is often a cost-effective alternative to upgrading to a PoE switch.

These devices convert fiber to copper and provide power to PoE-compliant devices, such as IP cameras and wireless access points. Media converters are typically used to extend a network beyond the limits of Ethernet.

A Power Sourcing Equipment (PSE) leaves its ports unpowered and periodically checks to see if anything has been connected—a process known as Signature Detection. This process uses low voltage to detect the presence of a Powered Device (PD) without damaging non-PoE devices. Once a PD’s signature is detected, the PSE supplies power based on the PD’s classification.

Power Classification is an optional step where the PD provides one of eight possible classification signatures, allowing the PSE to determine the amount of power required. If no classification is provided, the PD is considered Class 0, and 12.95W is allocated.

The PSE continues to monitor the power delivered to each PD. If a PD stops drawing power, the PSE stops supplying power, assuming the device has been disconnected. However, for devices like LED lights that may enter a low-power state, a Maintain Power Signature (MPS) reassures the PSE that the device is still present.

The IEEE P802.3bt standard recommends a minimum of Class D Cat5e cabling. For new installations, Cat6a is recommended as it allows for larger bundle sizes. For cable runs greater than 50 feet, use cables with solid 23 AWG conductors.

Higher power applications, such as Type 3 (60W) and Type 4 (100W), generate more heat, especially when cables are bundled. Underwriters Labs (UL) introduced the Limited Power (LP) Certification to simplify cable selection, indicating that the cable has been tested for higher temperature situations and can safely carry the current required.

PoE has a wide range of applications across several sectors:

Compared to traditional power solutions, PoE provides several advantages:

Implementing PoE in your network can be straightforward with the right equipment. Here’s what you need:

While PoE offers numerous benefits, there are some challenges to be aware of:

With PoE, powering your networked devices has never been easier or more efficient. Dive deeper into this technology and stay ahead in optimizing your business network!