PoE vs PoE+ vs PoE++: 802.3af, 802.3at, and 802.3bt Explained
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Power over Ethernet (PoE) sends electrical power and network data down the same Ethernet cable. Instead of running an outlet to every ceiling access point or rooftop camera, one cable from a PoE switch does both jobs. The catch is that PoE isn't one thing. There are three generations, PoE, PoE+, and PoE++, and each one delivers a different amount of power. Pick the wrong one and a camera won't boot or an access point runs with half its radios turned off.
Here's how they compare and how to choose.
PoE vs PoE+ vs PoE++ at a Glance
| PoE | PoE+ | PoE++ (Type 3) | PoE++ (Type 4) | |
|---|---|---|---|---|
| IEEE standard | 802.3af | 802.3at | 802.3bt | 802.3bt |
| Power at the switch port | 15.4 W | 30 W | 60 W | 90 W |
| Power at the device | 12.95 W | 25.5 W | 51 W | 71.3 W |
| Power classes | 0 to 3 | 4 | 5 and 6 | 7 and 8 |
| Wire pairs used for power | 2 | 2 | 4 | 4 |
The gap between the switch number and the device number is power lost as heat along the cable. Always size a device against the power at the device column.
PoE (802.3af)
The original standard from 2003. It delivers up to 15.4 W per port, with 12.95 W reaching the device. That's plenty for VoIP desk phones, basic fixed IP cameras, and simple Wi-Fi access points.
PoE+ (802.3at)
PoE+ doubled the power in 2009, to 30 W at the port and 25.5 W at the device. It covers gear like Wi-Fi 6 access points, video phones, and higher-powered security cameras. When a spec sheet asks for "802.3at" or "Class 4," it's asking for PoE+.
PoE++ (802.3bt)
PoE++ arrived in 2018 and uses all four pairs in the cable instead of two. It comes in two levels. Type 3 delivers 60 W at the port (51 W at the device) for gear like high-end Wi-Fi 6E and Wi-Fi 7 access points and PTZ cameras. Type 4 delivers 90 W at the port (71.3 W at the device) for the heaviest loads, such as outdoor PTZ cameras with heaters, small displays, and thin clients. You'll also see PoE++ called 4PPoE (four-pair PoE), and Cisco sells its own similar version called UPOE.
Which One Do You Need?
Start with the power draw on each device's spec sheet, then match the switch to the most demanding device on it. The standards are backward compatible, so a PoE++ switch will happily power a PoE+ or basic PoE device. The reverse isn't true. A PoE+ access point plugged into a basic PoE port may not power on, or may boot with features disabled.
If you're powering several devices, a PoE switch is the cleanest setup. If you only need to add power to one device on an existing network, a PoE injector sits between your regular switch and the device and does the same job for a single cable.
Power Classes and Your PoE Budget
Every PoE device reports a power class, from 0 to 8, during a short handshake with the switch. The class tells the switch how much power to reserve. Class 4 is the top of PoE+, Classes 5 and 6 are PoE++ Type 3, and Classes 7 and 8 are PoE++ Type 4.
The other number that matters is the switch's total PoE budget, the maximum wattage it can supply across all ports at once. A 24 port PoE+ switch with a 370 W budget can't run all 24 ports at a full 30 W, because that would take 720 W. Add up what your security cameras, access points, and IP phones actually draw, then pick a switch whose budget covers it with room to grow.
That handshake is also why standards-based PoE is safe for regular devices. A compliant switch checks for a PoE signature before sending any power, so a laptop or printer plugged into a PoE port simply gets data.
Cables and Distance
All three standards work up to 100 meters (328 feet), the normal limit for an Ethernet run. Cat5e cable handles all three standards. For PoE++, which pushes more current through all four pairs, Cat6 or Cat6A network cables stay cooler when many cables are bundled together, which helps on large camera and access point installs.
PoE+ and PoE++ FAQs
What is PoE+?
PoE+ is the common name for the IEEE 802.3at standard. It delivers up to 30 W per switch port, double the original PoE standard.
How many watts is PoE+?
30 W at the switch port and 25.5 W at the powered device.
What is PoE Class 4?
Class 4 is the highest power class in PoE+ (802.3at). A Class 4 device can draw up to 25.5 W, so it needs a PoE+ or PoE++ port.
Can a PoE++ switch power a PoE+ device?
Yes. PoE++ switches are backward compatible with PoE+ and standard PoE devices and only deliver the power each device requests.
How far can PoE run?
Up to 100 meters (328 feet) for PoE, PoE+, and PoE++, the same limit as standard Ethernet.