PoE Injector: What Is It and When Is One Needed?

A PoE injector adds electrical power to an Ethernet connection so a compatible device can receive both power and data through the same cable. It is commonly used when the existing network switch does not provide Power over Ethernet but a connected device requires PoE.

Instead of replacing the network switch, an injector can be installed between the switch and the powered device. This makes PoE injectors useful for adding individual devices or upgrading an existing network where only a limited number of PoE connections are needed.

How Does a PoE Injector Work?

A PoE injector typically has a data input, a PoE output and a connection to electrical power. An Ethernet cable from a non-PoE network switch connects to the injector’s data input. The injector then adds electrical power and sends the combined power-and-data connection through another Ethernet cable to the device.

The injector therefore does not replace the network switch or create the network connection. Its job is to add PoE power to an existing Ethernet link.

The device at the other end could be a wireless access point, camera, sensor, controller or another compatible Powered Device (PD). For a broader explanation of how Power over Ethernet technology supplies power to connected devices, see our introductory PoE resource.

When Is a PoE Injector Needed?

A PoE injector is most useful when a network already has a conventional Ethernet switch and only one or a few connected devices need PoE. Installing an injector can add that capability without replacing otherwise functional network equipment.

Injectors can also be useful when a particular device requires a higher PoE power level than the existing switch can provide. For example, an older switch may provide standard PoE or PoE+ while a new device requires a higher-power PoE++ connection. A compatible injector can provide the required power for that individual connection.

The injector must still support the power requirements and PoE standard of the connected device.

PoE Injector vs. PoE Switch: What’s the Difference?

The primary difference is where PoE power is added. A PoE switch provides network connectivity and PoE power directly from its PoE-enabled ports. A PoE injector adds power to an Ethernet connection coming from a switch that does not provide the required PoE power itself.

For a few devices, injectors may be a practical way to add PoE without changing the network infrastructure. As the number of powered devices increases, using individual injectors can become more complicated because each injector requires its own installation and power source.

Larger PoE deployments therefore commonly use network switches with integrated PoE capability rather than a collection of individual injectors.

How Much Power Can a PoE Injector Provide?

The amount of power depends on the injector. Models are available for different PoE standards, including PoE, PoE+ and PoE++. A higher-power injector may support applications requiring substantially more wattage than the original PoE standard could provide.

It is important to match the injector to the connected equipment rather than selecting one based only on its connector type. The injector’s IEEE PoE support and maximum output should be checked against the requirements of the powered device.

Our PoE power guide explains the different wattage levels available under PoE, PoE+ and PoE++.

Can a PoE Injector Provide 90W PoE++?

Yes. Injectors are available that support the higher power levels defined by IEEE 802.3bt, including Type 4 PoE++. This can provide up to 90 watts from the Power Sourcing Equipment, although the amount available at the powered device is lower because the standard accounts for losses through the cable.

A 90W PoE injector can be useful when a higher-power device needs to be added to a network that does not have a compatible PoE++ switch port. The rest of the network does not necessarily need to be upgraded simply to support that one connection.

For more detail on these standards, see PoE vs. PoE+ vs. PoE++.

Does a PoE Injector Increase PoE Distance?

A standard PoE injector should not be treated as a way to exceed normal Ethernet distance limits. Its primary purpose is to add electrical power to an Ethernet connection, not extend the allowable length of the network channel.

The standard Ethernet channel is generally limited to 100 meters, or 328 feet. Longer connections require a network design or extension method appropriate for the distance involved. Our guide to PoE distance covers those limits and options in more detail.

Is a PoE Injector the Same as a PoE Splitter?

No. The two devices perform almost opposite functions. A PoE injector combines power with an Ethernet connection, while a PoE splitter separates the power and data from a PoE connection near the endpoint.

A splitter can be useful when the network supplies PoE but the endpoint itself does not accept power directly through its Ethernet port. The splitter provides separate data and power outputs that can be connected to compatible equipment.