Power over Ethernet (PoE) Explained: Your Wi-Fi’s Best Friend, and More

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 proves mission (close to) impossible?

Don’t give up! That is when PoE, or Power over Ethernet, comes into play. This straightforward concept kills two birds with one stone.

There’s quite a bit to know about PoE; 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.

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 only one in this case. Plus, network cables are much easier to install than electrical wires—you won’t need an electrician.

PoE: Cables and device types

PoE works with all network cables. Generally, 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) to 10Gbps Multi-Gig.

But PoE involves more than just that cable itself. Let’s find out.

Generally, when plugging a device into power, we involve three items: the power source, the electrical cord, and the device itself.

Since we can’t connect a network cable directly to a wall socket, we 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, we’ll call it the power sender.

On the other end, the device that gets electricity over the network cable is officially called a powered device (PD) or a power receiver.

PoE power sourcing equipment (PSE) – Power sender

A power sender is a device that works as a power source. It has a power adapter to draw juice from a wall socket. Typically there are two main types of PSE:

• PoE switch: This switch looks and works like any network switch but with PoE-enabled network ports. Some routers also have PoE ports.
• PoE injector (or PoE adapter): A kind 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.

Extra: PoE Power senders and UPS

Generally, it’s not a good idea to use a PoE power sender, such as a PoE switch, with an uninterrupted power supply (UPS) unless it’s a PoE-specific UPS.

Most home and standard UPSes are designed for devices that, for the most part, draw constant power. PoE power senders, by nature, can abruptly draw acutely different amounts of power depending on the situation.

Consequently, using one with a standard UPS might cause unexpected results. It’s especially true with the PoE standards that can deliver high wattage—more below.

If you want to keep your PoE power senders safe, plug them into a surge protector.

PoE power device—Power receiver

A power receiver is the end device—such as an IP camera, a 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 capability to an existing device to turn it into a PoE power receiver.

On the receiving end, the device itself needs to have built-in PoE capability from the get-go. Also note that a PoE device must connect directly to a PoE power sender with no active device, such as a non-PoE switch, in between. However, a PoE connection works through a patch panel or a network coupler.

There is also hardware that works both as a PSE and a PD 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 first 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.

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.

This standard can deliver up to 15.4 watts of electrical power per connection. In real-world usage, however, generally, you can expect about 13 watts from it.

A PoE device (power receiver) will work with any power senders of the higher PoE standards below.

802.3at

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

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 (or higher) 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.

Active PoE’s advantages

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.

In other words, a PoE device (power receiver) will work with any PoE switches (power sender). The other way around, a PoE++ switch can power any device, be it PoE, PoE+, or PoE++.

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.

Typically, this type of PoE generally uses a proprietary injector that accompanies an end device (power receiver) and 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 as a cost-saving measure. 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, 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 one of the active PoE standards mentioned above.

PoE sourcing equipment (PSE) and non-PoE device

If 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 (active) 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 that a passive PoE injector (adapter) generally only accompanies a device that needs it. As a result, the chance you’d use one with a non-PoE device by accident is low.

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 both 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 in 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. The power injector or the PoE switch would likely take the hit first in case of a hazard.

PoE vs. Wi-Fi vs. Powerline

PoE extends a network to one device at a time and 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 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, PoE is faster and much more reliable in terms of network performance. When you can choose between the two, PoE is the way to go.

Powerline networking: It’s convenient, but you can’t consistently count on it

If you live in a large home, have a large warehouse, or want to place a network device outdoors 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 device with a PoE connection

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

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, and connect a network cable to its port. If it has more than one network port, use the port labeled PoE or PoE in.
2. Plug the other end of the cable directly into a PoE port of the power sender (PSE)—be it a PoE switch or an injector.
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 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.