Power over Ethernet (PoE): How It Works & Key Standards

Power over Ethernet (PoE) has transformed the way modern networks are built. Instead of running separate cables for power and data, PoE allows both to travel through a single Ethernet cable, making deployments faster, and far more flexible.

From IP cameras and wireless access points to industrial IoT devices, Power over Ethernet simplifies installations and enables devices to operate in places where traditional power sources are difficult to reach. But how does PoE work, what standards define it? Let’s take a closer look.

WHAT IS POWER OVER ETHERNET (POE)?

Power over Ethernet (PoE) is a networking technology that allows both power and data over Ethernet to be delivered through a single Ethernet cable. In simple terms, PoE technology enables network devices such as IP cameras, wireless access points, and sensors to receive electrical power and transmit data using the same cable, eliminating the need for separate power supplies. This approach simplifies installation, reduces cabling complexity, and makes it easier to deploy devices in locations where traditional power sources may not be available.

HOW DOES POE WORK?

To understand how PoE technology works, it helps to know the two main components involved: Power Sourcing Equipment (PSE) and Powered Devices (PD). The PSE, typically a PoE switch or a PoE injector, supplies electrical power through the Ethernet cable.

The PD is the device receiving that power, such as an IP camera, wireless access point, or IoT sensor. In most deployments, PoE delivers around 48V DC power together with data through the same cable, enabling efficient power and data distribution over Ethernet.

POWER SOURCING EQUIPMENT – POE SWITCHES AND INJECTORS

A PoE switch is the most common PSE device. It provides both network connectivity and power to multiple devices at the same time. Depending on network requirements, organizations can choose a managed PoE switch, which offers advanced monitoring and configuration features, or an unmanaged switch that is simpler to deploy.

POE IN, POE OUT, AND PASSTHROUGH EXPLAINED

The direction of power flow matters in PoE deployments. PoE In means a device receives power through its Ethernet port from a PoE source. PoE Out means the device can supply power onward to another connected device. Some devices support PoE passthrough, combining both – they receive power via PoE In and forward part of it through PoE Out to another device, such as an IP camera or access point.

ACTIVE POE VS. PASSIVE POE

Finally, it is important to understand the difference between active PoE and passive PoE. Active PoE follows IEEE standards like 802.3af, 802.3at, or 802.3bt, where the equipment first checks whether the connected device supports PoE before delivering power, ensuring safe operation. Passive PoE does not perform this check and continuously sends power through the cable. While simpler, passive PoE requires compatible devices to avoid potential damage.

POE STANDARDS AND POWER LEVELS

PoE standards define how much power can be delivered through an Ethernet cable and ensure compatibility between network equipment.

The most common standards include:

• IEEE 802.3af, which provides up to 15.4W,

• IEEE 802.3at (PoE+), delivering up to 30W, 

• IEEE 802.3bt (PoE++ or 4PPoE), supporting significantly higher PoE power levels of 60W or even 90W.

These standards make it possible to power a wide range of devices, from IP cameras and access points to more demanding equipment. When deploying PoE infrastructure, it is also important to consider the PoE power budget, which determines how much total power a switch can supply to all connected devices.

BENEFITS OF POWER OVER ETHERNET

One of the key benefits of PoE is the ability to power and connect devices using a single Ethernet cable. This significantly reduces installation costs by eliminating the need for separate electrical wiring and additional power outlets. PoE also simplifies network infrastructure, helping reduce cabling costs and making installations faster and easier to manage.

Because devices no longer depend on nearby power sources, PoE enables flexible device placement, allowing equipment to be installed exactly where it is needed. At the same time, centralized power management through PoE switches improves control, reliability, and scalability, making PoE a practical solution for modern networks and expanding infrastructure.

MOST COMMON POE USES

Power over Ethernet is widely used in Teltonika networking solutions to simplify deployments and power multiple devices through a single Ethernet cable. In smart city projects, PoE switches can power CCTV cameras, speakers, displays, and other infrastructure around EV charging stations, creating a clean and efficient network backbone. In industrial environments such as logistics warehouses, managed power over ethernet switches power devices like license plate recognition cameras, RFID scanners, and other monitoring equipment while enabling reliable network management.

Teltonika devices also provide PoE in urban surveillance and smart lighting systems, where switches and PoE routers simplify installation and help power distributed devices across large infrastructure deployments. Together, these applications show how PoE enables flexible, scalable connectivity for smart city, industrial automation, and infrastructure networks.

HOW TO CHOOSE THE RIGHT POE DEVICE

When deciding how to choose a PoE switch, it is important to evaluate several key factors based on the network environment and connected devices. First, consider the power requirements of all powered devices and perform a proper PoE power budget calculation to ensure the switch can supply enough power across all ports. Environmental conditions also play a critical role.

In industrial deployments, Teltonika PoE switches and routers are designed to operate reliably in challenging environments with temperature fluctuations, vibration, or dust. Network topology should also be assessed to determine the required number of ports, management features, and integration with routers or other infrastructure devices.

Finally, organizations should plan for scalability and future expansion, choosing solutions that allow additional devices or higher power demands as the network grows.

Not sure which PoE device fits your deployment? Contact our team and we’ll help you select the right fit for your project.