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NETWORKING · POWER

PoE vs PoE+ vs PoE++: The 802.3af, 802.3at and 802.3bt Standards

802.3af (PoE), 802.3at (PoE+) and 802.3bt (PoE++) are the three IEEE Power over Ethernet standards. They differ mainly in power per port, roughly 15 W, 30 W, and up to 60 to 90 W, with the higher tiers using all four pairs of the cable.

01

The Short Answer

The three standards are successive steps in how much power Ethernet can carry. 802.3af delivers about 15 W per port, 802.3at (PoE+) about 30 W, and 802.3bt (PoE++) up to 60 W (Type 3) or 90 W (Type 4). af and at use two of the four cable pairs for power; bt uses all four.

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    802.3af (PoE) ~15 W at the source, ~12.95 W at the device: cameras, VoIP phones, access points.
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    802.3at (PoE+) ~30 W: PTZ cameras, video phones, larger access points.
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    802.3bt Type 3 ~60 W: video conferencing, multi-radio access points.
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    802.3bt Type 4 ~90 W: PoE displays and panel PCs.
02

Which You Need

Match the standard to the most demanding device on the link, and remember the power available at the device is a little below the source figure because of cable loss. A PoE+ or PoE++ source covers most edge deployments.

See our guide to industrial Power over Ethernet for the full picture.