PoE, PoE+, PoE++: Powering Devices Over Ethernet
Power over Ethernet (PoE) lets you deliver both data and electrical power through a single Ethernet cable, eliminating the need for separate power supplies at each device. From IP cameras and WiFi access points to VoIP phones and door access controllers, PoE simplifies deployment and reduces cabling costs. This guide covers the IEEE standards, power budgets, and planning tips you need.
What Is Power over Ethernet?
Power over Ethernet (PoE) is a family of IEEE standards that enable network cables to carry electrical power alongside data. A PoE-capable switch or PoE injector acts as the power sourcing equipment (PSE), supplying DC voltage over the same Cat5e, Cat6, or Cat6A cable that carries your Ethernet data. The connected device — called a powered device (PD) — draws only the power it needs.
The key advantage is simplicity. Instead of running an Ethernet cable and a power cable to every access point on a ceiling or every camera on an exterior wall, you run a single cable. This reduces installation cost, eliminates the need for power outlets in difficult locations, and allows centralised power management from the switch — including the ability to remotely reboot devices by cycling the PoE port.
The Three PoE Standards Explained
There are three main IEEE standards for PoE, each delivering progressively more power. Understanding which standard your devices require is the first step in specifying the right switch.
PoE — IEEE 802.3af (up to 15.4 W)
The original PoE standard, ratified in 2003, delivers up to 15.4 watts per port from the switch, with approximately 12.95 watts available at the powered device after cable losses. This is sufficient for basic VoIP phones, simple fixed IP cameras, and entry-level wireless access points. 802.3af uses two of the four twisted pairs in the cable for power delivery.
PoE+ — IEEE 802.3at (up to 30 W)
Ratified in 2009, PoE+ doubles the available power to 30 watts per port (approximately 25.5 watts at the device). This covers more power-hungry devices such as PTZ cameras, WiFi 6 access points, thin-client terminals, and video intercoms. Most modern Ubiquiti UniFi APs (U6 Pro, U6 Enterprise) are PoE+ devices. Like 802.3af, it uses two cable pairs for power.
PoE++ — IEEE 802.3bt (up to 60–100 W)
The newest standard, ratified in 2018, comes in two types. Type 3 delivers up to 60 W per port (≈51 W at the device), and Type 4 delivers up to 100 W per port (≈71 W at the device). 802.3bt uses all four twisted pairs. WiFi 7 APs like the Ubiquiti U7 Pro XG require this standard, as do LED lighting panels, digital signage displays, and multi-radio enterprise APs.
PoE Standards at a Glance
| Feature | PoE (802.3af) | PoE+ (802.3at) | PoE++ Type 3 (802.3bt) | PoE++ Type 4 (802.3bt) |
|---|---|---|---|---|
| Max power at switch port | 15.4 W | 30 W | 60 W | 100 W |
| Max power at device | 12.95 W | 25.5 W | 51 W | 71.3 W |
| Cable pairs used | 2 pairs | 2 pairs | 4 pairs | 4 pairs |
| Minimum cable | Cat5e | Cat5e | Cat5e (Cat6A rec.) | Cat6A strongly rec. |
| Typical devices | VoIP phones, basic IP cameras | WiFi 6 APs, PTZ cameras, intercoms | WiFi 6E APs, LED lighting | WiFi 7 APs, displays, laptops |
| Year ratified | 2003 | 2009 | 2018 | 2018 |
Cable Distance and Quality
PoE operates within the standard Ethernet maximum of 100 metres from switch to device. Beyond this distance, both data and power delivery become unreliable. The cable has electrical resistance, and longer runs lose more power as heat — which is why the wattage available at the device is always lower than what the switch outputs.
Cable quality matters significantly. Poor or damaged cables have higher resistance, reducing power at the device and generating excess heat. For PoE++ at higher wattages, Cat6A cabling is strongly recommended. Cat6A has thicker conductors, lower resistance, and better shielding — resulting in more reliable power delivery over the full 100-metre run.
Installation tip: Always use solid-core Ethernet cable for permanent PoE runs, not stranded patch cable. Solid-core conductors have lower DC resistance, meaning less power loss and less heat. For PoE++ (802.3bt), invest in quality Cat6A and ensure all terminations are properly made and tested. Poor terminations are the leading cause of PoE reliability failures in the field.
Planning Your Switch PoE Power Budget
Every PoE switch has a total power budget — the maximum combined wattage it can deliver across all PoE ports simultaneously. This is separate from the per-port maximum. A 24-port PoE+ switch might have a 370 W budget; powering all ports at 30 W would require 720 W, so the switch denies power to lower-priority ports when the budget is exceeded.
In practice, most devices draw far less than the per-port maximum. A VoIP phone draws 5–7 W, a WiFi 6 AP draws 12–18 W, and a fixed IP camera draws 8–15 W. Add up the actual draw of every device you plan to connect, then leave at least 20% headroom for future growth and power spikes during device boot-up.
Power budget warning: If total device draw exceeds the switch budget, the switch will deny power to lower-priority ports — causing devices to go offline unexpectedly. Monitor the PoE consumption dashboard and configure port priorities so critical devices (APs and cameras) are always powered first.
Which Devices Need Which PoE Standard?
Matching the PoE standard to your device’s power requirement is essential. Always check the datasheet before specifying a switch.
PoE / 802.3af (up to 12.95 W): VoIP desk phones, basic fixed IP cameras, simple IoT sensors, and entry-level wireless access points.
PoE+ / 802.3at (up to 25.5 W): WiFi 6 access points, PTZ cameras, video door stations, wall-mounted thin clients. Most Ubiquiti UniFi APs including the U6 Pro and U6 Enterprise fall here.
PoE++ / 802.3bt (up to 71 W): WiFi 7 access points (Ubiquiti U7 Pro XG), high-performance PTZ cameras with heaters/wipers, LED lighting, and digital signage displays. Oversizing slightly is always preferable to running at the absolute limit.
Ubiquiti UniFi Access Points — PoE-Powered
Ubiquiti U6-Pro UniFi AP WiFi6 Indoor 5.3Gbps with 300+ Client Capacity - No POE Injector
Ubiquiti UniFi U6-Enterprise WiFi 6E 4x4 MIMO PoE+ Access Point,140m Coverage,600+ Device&2.5GbE Uplink, Ceiling Mount,For High-Density
Ubiquiti U7 Pro XG, White,Ceiling-mounted 6-stream WiFi 7 AP Wiith 10/5/2.5/1 GbE Support,140 m² Coverage, 300+ Connect Devices, Powered By PoE+
Ubiquiti U7 Pro Wall, 6 Spatial Strea,6 GHz Support Tailored,PoE+, Voltage 44â57V DC, Max Power 22W,2.5 GbE uplink,300+ Devices,140 m² cover
Ubiquiti Swiss Army Knife Ultra, Compact Indoor/Outdoor PoE Access Point, Flexible Mounting Support, Long-range Antenna Options
Frequently Asked Questions
Yes — PoE standards are fully backward compatible. The switch detects how much power a device needs via the IEEE 802.3 classification handshake and delivers only what is required. You will never damage a low-power device by connecting it to a higher-standard PoE port.
A PoE injector is a small inline device that adds PoE power to a standard Ethernet connection. Use one when your existing switch does not support PoE but you need to power one or two devices. For more than a handful of devices, replacing the switch with a dedicated PoE model is more cost-effective and far easier to manage.
No. Power and data travel independently on the cable. PoE power delivery has no effect on data throughput — a PoE Gigabit port delivers the same network performance as a standard Gigabit port.
Check the switch datasheet for IEEE 802.3bt compliance. The per-port wattage specification should show 60 W (Type 3) or 90–100 W (Type 4). Switches marked as PoE+ only support up to 30 W per port and will not deliver PoE++ power levels even if the device requests it.
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