PoE vs PoE+ vs PoE++: Power Standards Compared

PoE vs PoE+: A Practical Power Standards Comparison for Network Buyers

Power over Ethernet (PoE) has quietly become one of the most useful features in enterprise networking. A single cable delivers both data and electrical power to access points, IP cameras, VoIP phones, door controllers and a growing list of building-automation devices. For importers, distributors and system integrators, however, "PoE" is not one thing. The phrase covers three generations of standards — 802.3af, 802.3at and 802.3bt — with very different power budgets, device classes and cabling implications. Getting the match wrong between a switch port and a powered device is one of the most common causes of field failures, so this guide compares PoE vs PoE+ vs PoE++ in practical terms.

The Three PoE Standards at a Glance

The IEEE defines PoE in the 802.3 family. Each generation raised the amount of power available at the power sourcing equipment (PSE) — the switch — and at the powered device (PD) — the camera, phone or access point. Because some energy is lost as heat in the cable, the PD always receives less than the switch port can deliver, which is why power figures are usually quoted as a pair.

These are the standard-defined ceilings. A given switch may budget fewer watts across its total port count than the per-port maximum multiplied by the number of ports, so always check the switch's total power budget as well as its per-port rating.

802.3af (PoE): The Original Baseline

Ratified in 2003, 802.3af established the principle that data and power could share standard Ethernet cable. It delivers up to 15.4 W at the switch port, with 12.95 W guaranteed at the device after cable loss. For years this was enough for desk phones and fixed-focus cameras, and it remains the most common power class in voice deployments.

The trade-off is headroom. Modern wireless access points with multiple radios and higher-gain antennas, and cameras with pan-tilt-zoom motors, heaters or infrared illuminators, routinely exceed 12.95 W. Plugging such a device into an af-only port usually results in the device booting, drawing more than the port can supply, and then resetting in a loop — one of the classic PoE troubleshooting scenarios.

802.3at (PoE+): The Current Mainstream

The search question "poe vs poe+" usually comes down to whether 15.4 W is enough. 802.3at, ratified in 2009, doubles the per-port ceiling to 30 W at the PSE and 25.5 W at the PD. That headroom comfortably covers most 802.11ac and Wi-Fi 6 access points, PTZ cameras and video-enabled desk phones.

Two practical points matter for buyers:

• Compatibility is backward-looking. A PoE+ switch port can generally power an 802.3af device, and an af device plugged into a PoE+ port simply draws what it needs. The reverse is not true: an at device on an af port will be underpowered.
• Device class matters as much as the standard. Both af and at define numbered classes (0 through 4) that tell the switch how much power to reserve before the device is fully powered. Class 4 exists only under 802.3at and signals a device that may draw up to the full PoE+ budget.

For most new deployments, PoE+ is the sensible floor for access points and cameras. Specifying af-only switches to save on unit cost frequently comes back as service calls once a customer upgrades a camera model two years later.

802.3bt (PoE++ Types 3 and 4): Higher Power over Four Pairs

The 2018 802.3bt amendment split into two types. Type 3 delivers up to 60 W at the PSE and 51 W at the device; Type 4 raises this to 90 W and 71.3 W respectively. The key architectural change is that 802.3bt uses all four pairs of the cable rather than two, which is also how it maintains compatibility with existing cabling.

802.3bt introduces new device classes (classes 4 through 8, with class 4 shared with 802.3at) and a feature called Autoclass, which lets the switch measure the device's actual draw and reallocate reserved power. That matters on switches with a fixed total budget: smarter allocation means more devices can share the same supply.

Typical PoE++ candidates include ceiling-mounted Wi-Fi 6E/7 access points with high spatial streams, pan-tilt-zoom cameras with heaters and wipers, point-of-sale terminals, digital signage and PoE lighting controllers. Outside these categories, most buyers do not yet need Type 4, and paying for 90 W ports on every position is rarely justified.

Cabling, Cable Length and Heat

PoE standards were written to run over standard twisted-pair Ethernet, but higher power levels put more stress on the physical layer. A few rules of thumb help specifiers avoid problems:

• Use copper, not CCA. Copper-clad aluminium cable has higher resistance than solid copper and is a poor choice for PoE, particularly at PoE+ and above. Voltage drop over long runs can push a device below its minimum operating voltage.
• Stay within 100 metres. That is the standard channel limit for twisted-pair Ethernet, and it applies to PoE as well. Longer runs mean more loss and, at higher power, more heat.
• Mind the cable gauge. Higher power over thinner conductors produces more heat in the bundle. Where many high-power devices share a conduit, check the cable's temperature rating and bundling guidance.
• Check the total budget, not just per-port watts. A switch rated at 30 W per port may budget only a fraction of that across all ports simultaneously.

How to Match PoE Switches to Powered Devices

Good PoE planning starts from the device list, not the switch catalogue. Work through the following steps:

• List every PD and its power draw. Manufacturers publish maximum consumption; use that figure, not the idle draw.
• Compare against the standard, not the marketing label. A device needing 20 W is a PoE+ device regardless of what the box says.
• Leave headroom. Motorised cameras and APs with bursty radios can exceed their nominal draw. Reserve a margin of roughly 20 percent per port and per switch.
• Standardise upward where practical. Buying PoE+ as the baseline and reserving PoE++ for designated high-power positions keeps both capital cost and spare-parts complexity down.
• Plan the uplink and management layer. PoE is only half the story; the switch still needs adequate uplink bandwidth and the management features your customer expects.

For integrators building repeatable bill-of-materials templates, a mixed fleet is often the right answer: a large block of PoE+ access ports for phones, cameras and APs, plus a smaller number of PoE++ ports for high-draw positions such as ceiling APs and PTZ cameras. When you are ready to specify, browse our range of PoE switches to compare port counts, power budgets and standards support, or go straight to our 48-port PoE switches for dense access-layer deployments.

Frequently Asked Questions

Is PoE+ backward compatible with PoE?

Yes. An 802.3at port can power an 802.3af device, and the device will draw only what it needs. The reverse — an at device on an af port — is where underpowering occurs.

Does PoE vs PoE+ matter for cable choice?

Both run on standard twisted-pair cable, but PoE+ benefits from solid copper conductors and attention to bundling and heat, especially over long runs.

Can I mix PoE, PoE+ and PoE++ devices on one switch?

Generally yes, provided each port supports the standard the device requires and the switch has enough total power budget for the combined load. Devices negotiate their class with the switch automatically.

Do I need PoE++ for Wi-Fi 6 access points?

Not necessarily. Many Wi-Fi 6 APs are PoE+ devices; higher-end models with more radios and streams may require 802.3bt. Always check the AP's published power requirement.

Sourcing Note

Hui Tong supplies original, brand-new network switches from Cisco, Juniper, Huawei, Dell, Fortinet, Moxa and other brands, with a minimum order from 1 unit, payment by T/T, D/P or D/A, and a 1-year warranty. Offices and warehouses in Shanghai, Beijing, Wuhan and Shenzhen support exports to North America, Europe, the Middle East, Southeast Asia, Africa and Oceania. For PoE and PoE+ switch requirements, review our PoE switches and 48-port PoE switches, then send your device list and power budget for a tailored quotation.