What Is Power over Ethernet (PoE)?

Thanks to technological developments such as Power over Ethernet (PoE), there is no longer a need for separate power cables to operate a single device. PoE systems eliminate the need for electrical outlets and bulky power adapters, allowing devices to connect to the Internet using only one cable. In this article, learn what Power over Ethernet is, how it works, and its many uses to optimize Internet access.

What is Power over Ethernet?

Power over Ethernet (PoE) is a technology that delivers electric power and data signals to connected devices over a single Internet cable. Though you still need to run a network cable, you only need one cable rather than multiple for different connections.

Under normal circumstances, Internet of Things (IoT) devices, like digital cameras, need both power and data connection using two separate PoE. Power over Ethernet drastically simplifies this type of wiring setup; both connections - electrical and network - join into a single cable, cutting down the amount of copper required for a successful device and eliminating the need for separate power supplies and outlets.

PoE allows network installers to deploy powered devices in hard-to-reach locations that have a limited local power source. Because of this, most businesses today rely on Power over Ethernet to supply electricity over existing data cables to IP phones, firewalls, WiFi access points, and other important parts of network infrastructure.

Power over Ethernet has revolutionized how small- to medium-sized network devices are integrated into modern networks.

A router with PoE (Power over Ethernet) ports

How does Power over Ethernet work?

PoE technology involves integrating power and data on the same cable. Instead of using an outlet or adapter to power devices, PoE-enabled devices receive electrical current from a single Ethernet cable connected to a local area network (LAN). Power over Ethernet requires two key components: power sourcing equipment (PSE) and a powered device (PD) that can receive power over Ethernet.

The PSE refers to the network switch or midspan power injector that provides power to the Ethernet cable. Power over Ethernet combines this power with data; the midspan injector injects a low voltage DC power onto the Ethernet cable. Users typically install the injector near the Ethernet switch or hub.

Then, the device that receives this power - called a PoE-enabled device - receives power through the Ethernet cable. PoE devices like IP phones, PoE cameras, or wireless access points can then operate normally without requiring a standalone power source.

Two factors limit the amount of power that can travel over Ethernet cabling: how much power the midspan injector can provide and the resistance of the cable itself.

Benefits of Power over Ethernet

Power over Ethernet technology has a number of benefits which are outlined below.

  • Simple installation and flexibility. PoE simplifies the installation process by letting customers use a single Category5, 5e, or 6 cable for both power and data, which allows you to deploy devices in locations where an electrical outlet may not be easily accessible.
  • Cost-effective. PoE reduces overall installation costs by reducing the need for hardware, power outlets, and associated installation labor. It can reduce deployment costs by up to $1000 per device.
  • Reliable and scalable. PoE achieves a more resiliant network by doing away with additional power infrastructure.
  • Provides centralized power management. This technology allows you to monitor and control the power consumption of your entire network.
  • Energy-efficient. Power over Ethernet helps reduced energy consumption by only providing power when needed. With PoE, power can automatically turn off to devices not in use.
  • Safe and secure. PoE devices are designed to be safe, with built-in protection mechanisms that prevent overloading, short-circuiting, and electrical damage.

Applications of Power over Ethernet

Power over Ethernet technology has several benefits, including cost savings, increased flexibility, and simplified installation. The most common types of PoE applications include security cameras, VoIP phones, and wireless access points.

IP cameras used for surveillance are one of the most popular applications of PoE technology. Power over Ethernet eliminates the need for a separate power source, which can be difficult to install in certain locations. Power over Ethernet cameras don't need tethered to a power cable; installers can place them in areas that don't have access to power outlets, such as outdoor locations or ceilings, without requiring the extra cost of additional wiring.

PoE also commonly powers VoIP or IP phones. PoE makes it easier to deploy phones in locations where power outlets aren't available, like conference rooms or open workspaces.

Additionally, wireless access points rely on PoE technology, as it allows for greater flexibility in the location of these wireless access points. Instead of being limited to locations near power outlets, access points can be installed in areas that provide the best WiFi coverage.

Power over Ethernet also powers other devices like ATMs, security card readers, IP intercoms, PoE lighting, and IP clocks.

Where can you use PoE devices?

You can install Power over Ethernet devices in a wide range of locations depending on the specific application. This includes:

  • Offices, because they use VoIP phones, wireless access points, and IP cameras
  • Retail stores, because they use point-of-sale terminals, digital signage displays, and surveillance cameras
  • Schools and universities, because they use classroom projectors, smartboards, and security cameras
  • Healthcare facilities, because they use IP phones, medical devices, and nurse call systems
  • Warehouses, because they use time clocks, inventory management systems, and security cameras
  • Outdoor environments, because they use PoE camera systems, wireless access points, and traffic systems
  • Industrial environments, because they use sensors and cameras

Essentially, PoE devices work in any place where a network device requires power.

Power over Ethernet standards

Power over Ethernet technology relies on different standards set by the Institute of Electrical and Electronics Engineers, which governs how networking equipment should operate. This governing body not only creates standards for Ethernet but also for data communications. They define the maximum amount of power that can be delivered and the maximum distance that power can be transmitted.

Below is a chart summarizing the PoE standards, followed by an explanation of each standard, in order to help you choose the right PoE solution for your network.

StandardNameMaximum Power OutputCable TypeMax Cable Length
IEEE 802.3afPoE15.4WCat5e100m
IEEE 802.3atPoE+25WCat5e100m
IEEE 802.3bt4PPoE or PoE++Up to 90WCat5e or Cat6100m

IEEE 802.3af

IEEE 802.3af is the original PoE standard released in 2003. It provides up to 15.4 watts of DC power over a Cat5. This standard is suitable for powering devices with low power requirements, such as Voice over Internet Protocol phones, wireless access points, and IP cameras.

This PoE standard works for devices that require low power and with a maximum distance of 100 meters.

IEEE 802.3at

Over time, new devices began to require more power, so the IEEE 802.3at standard (PoE+) was introduced in 2009. In real-world usage, it supports up to 25 watts of power over a Cat5.

The standard is ideal for delivering power to devices with higher power requirements, such as video conferencing equipment and high-performance wireless access points. It supports a maximum distance of 100 meters.

IEEE 802.3bt

Popularly known as 4PPoE (PoE++ Type 3), IEEE 802.3bt was released in 2018. It can deliver up to 90 watts of power over four pairs of an Ethernet cable at Cat5 or better.

This standard, therefore, works best for powering devices with high power requirements, like PTZ cameras, thin clients, and building automation systems.

It's important to note that PoE standards are distinguished by the amount of power they can provide as well as the requirements for the powered device and the Ethernet cable used to transmit power.

What are the Power over Ethernet classes?

Power over Ethernet defines four classes that detail the power specifications of a powered device. These classes are based on the amount of power they require, and they are used to ensure that the Power over Ethernet switch or power sourcing equipment doesn't deliver more power than the device can handle.

The four PoE classes are:

  • Class 0: This class specifies that the device requires no power. Typically, this class disables PoE functionality.
  • Class 1: This class requires a maximum of 3.84 watts of power.
  • Class 2: This class provides up to 6.49 watts of power.
  • Class 3: This class requires a maximum of 12.95 watts of power.

Devices that require more than 12.95 watts of power are typically referred to as being PoE+, or 802.3at-compliant.

Which Ethernet cables support PoE?

Power over Ethernet works with nearly all network cables. However, you need a high quality Ethernet cable that can deliver power and data without interference. The performance of cables can vary depending on the type of Ethernet cable you choose.

Generally, Category 5 (Cat5) Ethernet cables made of pure copper work better for PoE rather than cable made with copper-clad aluminum wiring, as copper is a better conductor than aluminum.

What's the difference between power sourcing equipment (PSE) and a powered device (PD)?

Power over Ethernet involves more than just the Internet cable itself. The system consists of two primary components: the power sourcing equipment and the powered device.

Power sourcing equipment

The PSE is the power source for PoE operation. It can either be a PoE network switch that provides power and data over an Ethernet cable, or it can be a PoE injector which is installed between a non-PoE switch and a PoE-enabled device.

The PSE negotiates with the PD to determine the optimal power level based on its PoE class, power requirements, and cable length. PSEs can deliver different levels of power based on the PoE standard used.

The PSE is also called the power sender. Typically, there are two main types of PSE:

  • The Power over Ethernet switch. The PoE switch infuses power to the Ethernet cable to provide power to PoE-enabled devices. It looks like any other network switch.
  • The Power over Ethernet injector. The PoE injector is a type of Ethernet coupler that plugs into a wall socket to draw the required voltage from an external power source and then inject it into the Ethernet cable.

Powered device

The powered device, on the other hand, is the endpoint device that receives power from the PSE. It includes a PoE interface and a DC converter that can accept power from the PSE and convert it to the voltage required by the device.

The PD is also designed with the required protection mechanisms to guard against a number of current-related issues.

Frequently asked questions

Is Power over Ethernet safe?

As long as the standards are enforced, yes, Power over Ethernet is safe. Make sure you are using the cable correctly and following the codes. However, the technology reduces the electric shock risk by providing a low-voltage power source to devices, making it safer than traditional power sources regardless.

Can PoE cause damage to non-PoE devices?

No, Power over Ethernet adapters, injectors, and switches won't cause damage to non-PoE devices. However, since PoE provides a lower voltage, it's important to ensure that the connecting device also runs on that specific voltage in order for it to work correctly.

Can PoE work with Gigabit Ethernet?

Yes, Power over Ethernet works with Gigabit Ethernet as long as all other devices connected to the network use that same protocol.

Power over Ethernet works with any standards-compliant Ethernet solution that supports IEEE 802.3af or higher. It can also provide up to 25.5 watts of power per port for advanced applications such as wireless access points.

Does PoE work with PoE+ devices?

Yes, PoE and PoE+ are compatible. PoE+ is an extended version of the IEEE 802.3af standard, so any device compliant with that standard will be compatible with a PoE+ switch. However, not all devices will take advantage of the additional power available from PoE+.

For best results, only use PoE+ compliant devices when connecting them to a PoE+ switch.

Do all network devices support Power over Ethernet?

Not all network devices support Power over Ethernet (PoE). However, there are a growing number of network devices that do support PoE.

What is Ethernet over Power?

Ethernet over Power uses existing wiring to create an Ethernet network. It's similar to Power over Ethernet in that it both consolidates and eliminates additional external needs.