PoE Switch: What Is It and How Does It Work?

In Power over Ethernet smart building infrastructure, a PoE switch is a network switch that can provide both data connectivity and electrical power through Ethernet cabling. Instead of connecting a device to Ethernet for data and a separate electrical source for power, compatible equipment can receive both through a single network connection.

PoE switches are widely used for devices such as wireless access points, IP cameras and phones. Higher-power PoE has expanded their role in intelligent buildings, where Ethernet infrastructure can also support lighting, sensors, controls and other connected equipment.

How Does a PoE Switch Work?

A PoE switch performs the normal functions of an Ethernet network switch while also acting as Power Sourcing Equipment (PSE). When a device is connected to a PoE-enabled port, standards-based equipment determines whether that device can accept PoE and establishes the appropriate power requirements.

The switch can then supply electrical power while Ethernet data travels over the same cabling. This process allows compatible devices to be connected without requiring a separate electrical outlet at every endpoint.

The device receiving power is known as the Powered Device (PD). Depending on the application, that could be a camera, access point, sensor, controller or another PoE-compatible device.

How Much Power Can a PoE Switch Provide?

The amount of PoE power available from an individual port depends on the PoE standard supported by the switch. Older Type 1 PoE equipment can provide up to 15.4 watts from the PSE, while Type 4 PoE++ can provide up to 90 watts at the port.

A switch may support one PoE level across all ports or offer different capabilities depending on the model and configuration. The powered device must also be compatible with the available PoE standard.

For a detailed comparison of the different power levels, see PoE vs. PoE+ vs. PoE++: What’s the Difference?

What Is a PoE Switch Power Budget?

Port capacity and total switch capacity are two different things. A PoE switch may have ports capable of supplying relatively high wattage while still having a maximum amount of power that can be distributed across all connected devices.

This total available capacity is called the PoE power budget. For example, connecting many higher-power devices can consume the available budget even when additional physical Ethernet ports remain unused.

Power budgeting becomes especially important in larger intelligent building deployments with many connected devices. We cover the calculation and sizing process separately in How Do You Calculate a PoE Power Budget?

What Is the Difference Between a Managed and Unmanaged PoE Switch?

An unmanaged PoE switch provides basic network connectivity and PoE power with little or no configuration. These switches can be useful for simple installations where advanced network control is not required.

A managed PoE switch provides additional network configuration, monitoring and management capabilities. Depending on the equipment, administrators may be able to configure ports, monitor network activity, manage VLANs, view device status and control other network functions.

Commercial buildings and enterprise networks generally require more visibility and control than small standalone installations, making managed network infrastructure particularly important as the number of connected devices grows.

What Is a PoE++ Switch?

A PoE++ switch supports the higher power levels introduced under IEEE 802.3bt. Type 3 can provide up to 60 watts from the PSE, while Type 4 can provide up to 90 watts.

These higher power levels allow Ethernet infrastructure to support equipment with greater electrical requirements than earlier PoE generations could handle. This has helped expand PoE into building systems such as LED lighting, controls and other intelligent infrastructure.

Not every port labeled PoE supports PoE++. When specifying equipment, the supported IEEE standard and available wattage should be verified rather than assuming all PoE switches provide the same amount of power.

PoE Switch vs. PoE Injector

A PoE switch combines network switching and PoE power delivery in the same equipment. A PoE injector, by comparison, adds PoE power to an Ethernet connection when the network switch itself does not provide it.

Injectors can be useful when PoE is needed for a limited number of devices without replacing existing network equipment. When many powered devices are being deployed, a PoE switch can provide a more centralized approach.

See What Is a PoE Injector and When Is One Needed? for a detailed explanation of that equipment and where it fits into a network.

How Are PoE Switches Used in Intelligent Buildings?

In an intelligent building, the PoE switch can become part of the infrastructure connecting building devices to the IP network while also supplying their power. This creates a common network foundation for devices that historically may have relied on separate power and control systems.

The exact switch architecture depends on the number and location of devices, their power requirements and the building’s network design. PoE distance, total power budget and cabling requirements all need to be considered when determining where switches are located and how devices are connected.

As more building systems become network-connected, the PoE switch serves not only as a network component but also as a centralized point for distributing and managing power to connected devices.