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Power over Ethernet (PoE) Explained: Why It’s Your Wi-Fi’s Best Friend

So, you want to blanket your sprawling property with fast Wi-Fi, but extending electrical power to the far side of your yard or that tight corner in your attic prove mission (close to) impossible?

Don’t give up! That is when PoE, or Power over Ethernet, comes into play.

This is a straightforward concept where you can kill two birds with one stone. There’s quite a bit to know about PoE, and you’ll find it all here, with a minimum amount of technical jargon.

Dong’s note: I first published this post on March 5, 2019, and updated it on August 16, 2021, to add up-to-date, relevant information.

EnGenius EWS850AP Wi Fi 6 Access Point 14
An example of a Power over Ethernet (PoE) end-device (PD).

What is Power over Ethernet

Power over Ethernet is when you use one network cable — CAT5e, CAT6, or a higher grade — to deliver data signals and electric power to a device.

Yes, you still need to run a wire, but just a single one. Plus, network cables are much easier to install than electrical wires — you won’t need an electrician.

See also  How to Get your Home Wired with Network Cables (Almost) Like a Pro

PoE: Cables and device types

PoE works with all network cables. Generally, though, a higher-quality cable (pure copper) is always better for PoE than a lower-quality one (copper-clad aluminum).

As for network speed, PoE adheres to the general standards of network cables. Currently, PoE is available from Fast Ethernet (10/100 Mbps) all the way to 10Gbps Multi-Gig.

But PoE involves more than just that cable itself. That’s because, generally, when plugging a device into power, we actually involve three items: the power source, the cable, and the device itself.

Since you can’t connect a network cable directly into a wall socket, you need something at this end to facilitate the power draw.

In the world of PoE, this device, the one that delivers power, is officially called the power sourcing equipment (PSE). For the sake of simplicity, it’s also called the power sender.

The device that gets electricity over the network cable is officially called a powered device (PD) or a power receiver. Let’s find out more about them.

Power sourcing equipment (PSE) – Power sender

A power sender is a device that works as the source of the power; you connect one end of the network cable to this device.

This end also links to a router or a switch. A PSE device always has a power adapter to draw juice from a wall socket.

A typical example of a PSE device is a PoE injector (or a PoE adapter), a type of Ethernet coupler that also plugs into a wall socket.

Injectors are popular because they add PoE capability to an existing regular switch or router. Alternatively, there are PoE switches or PoE routers with built-in PoE capability for some or all of their network ports.

Here’s how to use an injector:

  1. Plug it into power. All PoE injectors come with a power adapter.
  2. Connect its non-PoE network port to an existing switch or router.
  3. Connect one end of a network cable into its PoE port. This cable now becomes PoE-ready and can be use to deliver both data and power to a PoE device.
EnGenius EWS850AP PoE Adapter 1
A typical PoE injector (adapter) is a power adapter that has two network ports. The PoE port delivers both data signals and power to a Power over Ethernet end-device whole the regular network port connects to a switch or router of an existing network. The injector itself has a power adapter.

Powered Device (PD) – Power receiver

A power receiver is the end device — such as an IP camera, an Wi-Fi access point, or a Voice over IP phone — that’s PoE-ready.

You connect the other end of the PoE-ready network cable mentioned above to this device, and it’ll get both power and data signals.

Unlike the case of the PSE (power source/sender) above, you can not add PoE to an existing (power receiver) device. On the receiving end, the device itself needs to have built-in PoE capability from the get-go.

But sometimes, though rare, we do have both PSE and PD in a single hardware unit, for PoE Forwarding. An example is when a PoE camera has a second PoE-ready network port to power another PoE camera in a daisy-chain setup.

For this to work, the PSE must deliver enough power for both PoE devices, bringing us to different PoE standards.

Power over Ethernet standards: Range and wattage

There are two types of PoE, active and passive. Both have a range of about 300 feet (100 m), which is the general max length of the network cable that connects a power sender and a power receiver.

Active PoE

Active PoE provides a safety mechanism for end devices (PDs).

With active PoE, devices perform a power check, called a handshake, before power is delivered. As a result, if the incoming electricity doesn’t meet the requirements, the power receiver won’t power up at all.

There are three primary standards for active PoE, including IEEE 802.3af, IEEE 802.3at, and IEEE 802.3bt. Since IEEE is short for the Institute of Electrical and Electronics Engineers, we can leave it out of the names for short.

802.3af

Also known as Type 1 PoE. This standard is the original (defined in 2003) and is still popular. It can deliver up to 15.4 watts of electrical power. In real-world usage, however, generally, you can expect about 13 watts from it.

802.3at

This standard is also known as PoE+ (PoE Plus) or Type 2 PoE. Available starting 2009, 802.3at provides up to 25.5 watts of power.

The 802.3at standard is backward compatible with 802.3af — its power senders (PSE) can support 802.3af receivers (PDs).

However, 802.3at power receivers (PDs) generally require an 802.3at power sender to work.

802.3bt

The 802.3bt or 802.3bt-2018, as the name suggests, became available in 2018 and further expanded the power capabilities of 802.3at. It has a few other names, including PoE++ (PoE plus plus) and 4PPoE.

802.3bt has two power outputs: 51W delivered power (Type 3 PoE) and 71.3 W delivered power (Type 4 PoE).

The 802.3bt standard’s power sender (PSE) is backward compatible with power receivers of previous active PoE standards. When applicable, it can easily deliver power to multiple PoE devices of lower standards in a PoE Forwarding setup.


The main advantage of active PoE is when a device belongs to a particular standard, it will work with all equipment of that standard from any vendors.

On top of that, a standard end device (power receiver) will work with any standard power sender of the same or higher tier. Newer standard PoE power devices might work with a lower-tier standard power sender but at a lesser capability.

But being part of a standard can be restrictive, and making standard devices means you have to adhere to all sorts of requirements — it can be expensive. This is where passive PoE comes into play.

Passive PoE

Generally, a passive PoE device is one that doesn’t belong to one of the 802.3x standards mentioned above.

This type of PoE generally uses a proprietary injector that accompanies an end device (power receiver) and which only works with that particular device.

Passive PoE doesn’t adhere to a standard, and the vendor has the freedom to specify its own electrical specs. With passive PoE, electricity is passed to the end device (PD) immediately without a compatibility check.

For this reason, generally, it’s a good idea not to use a passive PoE injector with an active PoE receiver and vice versa. That can be similar to plugging a 110V device into a 220V outlet.

So, if you choose to use a passive PoE end device, it’s a good idea to only use it with a passive PoE power sender that comes with it.

But before you get scared, the good news is, for ease of use, many passive PoE end-devices (PDs) on the market also support a particular active PoE standard.

PoE Passive vs Active
Many PoE devices support both Passive and Active PoEs.

Extra: PoE sourcing equipment (PSE) and non-PoE device

In case you wonder if you can use a non-PoE networking device, which most networking devices are, with PoE sourcing equipment — or power sender — such as a PoE switch. The answer is this depends.

Basically, any standard PoE PSE also works as non-PoE equipment. So if you plug a non-PoE device, such as a printer, into a PoE switch, it’ll work just like when you plug it into a non-PoE switch. In this case, the PoE switch is smart enough not to deliver any charge.

However, generally, you don’t want to use a passive PoE power sender with a non-PoE device. In most cases, nothing will happen, but you never know.

The good news is, a passive PoE injector (adapter) is generally available with a device that works with it. As a result, the chance of you using it with a non-PoE device is close to zero.

In short, the extra cost aside, it never hurts to get a standard PoE switch, even if you don’t have any PoE devices yet. You can use such a switch with PoE and non-PoE equipment.

Why Power over Ethernet is cool

The way it works, PoE eliminates the need for a wall power socket near the end device (PD) itself. And that implies a couple of important things:

  • Flexibility: You can run a network cable to any place, including tight corners. Without the need for an electrical outlet, the end device can stay anywhere, including outdoor areas.
  • Decluttering: PoE can significantly reduce the number of wires since you won’t need to use a power cord, making it an excellent choice for office devices, such as an IP phone.
  • Savings: You won’t need to spend time (and money) to install electrical wiring and power sockets, which would require a licensed electrician if you want to do it right.

(Again, running network cables generally doesn’t require an electrical license and is reasonably straightforward. Network cables are also relatively affordable; you can find high-end CAT6 in bulk for about $150 per 1000 feet.)

On top of that, PoE is reliable — it’s real wiring, after all. PoE devices are also safe from common power-related issues, such as power surges, overload, or bad wiring. In case of hazard, the power injector or the PoE switch would likely take the hit first.

PoE vs. Wi-Fi vs. Powerline

PoE extends a network to one device at a time and, therefore, cannot replace Wi-Fi. But it can enhance Wi-Fi coverage.

For example, using PoE access points, you can easily extend your Wi-Fi network to an area that doesn’t have a power socket (like the ceiling of a warehouse or the middle of a big yard) without compromising the performance.

On the other hand, Powerline is generally the opposite of Power over Ethernet — it’s useful when there are power sockets at a place where network cables can’t reach.

However, in terms of network performance, PoE is faster and much more reliable. That said, when you can choose between the two, PoE is the way to go.

See also  No Wi-Fi at that Corner? Maybe Consider a Pair of Powerline Adapters

In all, if you live in a large home, have a large warehouse, or want to place a network device outdoor or at an odd place, PoE comes in handy. It’s a much faster and more affordable solution than installing power cables and receptacles.

How to set up a PoE connection

How to specifically put together a PoE network depends on the devices you use. However, they all share the same hardware setup process.

A Power over Ethernet Setup
Here’s a typical Power over Ethernet setup (from the bottom up): Router, injector, and a PoE device.

Here are the typical steps you can follow in any order (make sure you don’t mix passive PoE and active PoE devices):

  1. Place the end-device (PD) where you want, connect a network cable to its network port. If it has more than one network ports, use the port labeled PoE or PoE in.
  2. Plug the other end of the cable to the PoE sender (PSE) — be it a PoE switch or an injector. If you use an injector, make sure you use the PoE port, then connect its other network port to your switch or router, using another network cable. (Note: You can use PoE via a patch panel or a long cable that consists of two short ones linked together via a network coupler.)
  3. Connect the PoE sender to the power and the existing network.

And that’s it. Now the Power over Ethernet end-device is part of your network. From the networking point of view, PoE and non-PoE devices are the same. The way they get power doesn’t affect how they function or their performance.

The takeaway

In my book, getting your home wired is always the way to go when it comes to top-notch network performance, even when you want Wi-Fi. And Power over Ethernet makes it even better.

You can use Multi-Gig access points, such as the Netgear WAX630/WAX620, EnGenius EWS850AP, EnGenius ECW230, and a PoE switch to quickly blanket a large property with Wi-Fi 6 without having to worry about electrical wiring or sacrificing performance.

In many ways, Power over Ethernet is networking as seriously as can be.

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13 thoughts on “Power over Ethernet (PoE) Explained: Why It’s Your Wi-Fi’s Best Friend”

  1. Which would be the best buy ASUS AX XT8 for Wifi 6 or Wifi 6E?
    Can I used a PoE Cat 6 cable between units to facilitate 2nd unit?

    Reply
  2. Happy New Year Dong!

    Just got Starlink Beta and the PoE powers the dish and the router which is a very cool setup. However I have doubts the supplier router will be sufficient for the entire house. I would like to plug in my old router and based on my understanding I should be good to go, my old router will not ask for power so there should be no sparks or smoke…do you agree?

    Reply
    • I don’t know what your old router is, Daniel. So check the post again regarding the PoE standard. Generally, you don’t want to use a passive PoE injector with a standard PoE device.

      Reply
  3. You mention PoE range of about 300 ft. If my Cat5e run is approaching this (about 250ft) and there is at least 1 maybe 2 or 3 couplers in-between (not including patch panel, keystone jacks, etc.) extending the cable run, do you think the PoE device will not function as intended? (PoE wireless access point)
    Trying to decide whether to get a PoE unmanaged switch or save some money and get a basic unmanaged switch 🙂

    Reply
  4. When connecting from the PoE power source device and the receiver, is it OK to use cat6 wire to go from a patch panel at the router to an RJ-45 jack for the receiver? I want to connect the camera and the PoE power source with short cables into the jack and the patch panel. Stated another way, do patch panels and RJ-45 jacks maintain the power from source to receiving device?

    Reply
    • Yes, Richard. You can think of the patch panel, this case, as stitching two short cables into a long one. I’ll work fine.

      Reply

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