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A Comprehensive Guide to the Three Major PoE Standards: 802.3af / 802.3at / 802.3bt

2026-07-10

What Is PoE?

PoE (Power over Ethernet) lets one standard Ethernet cable carry both data and electrical power — no separate power wiring needed. The PSE (e.g. a PoE switch) provides power; the PD (e.g. an IP camera) receives it. Three IEEE standards define increasing power levels:

A Comprehensive Guide to the Three Major PoE Standards: 802.3af / 802.3at / 802.3bt 1

802.3af — The Foundation

The first PoE standard (2003). Delivers up to 15.4W from the PSE, 12.95W at the PD after cable loss. Uses 2 pairs at 48V. Ideal for IP phones, basic APs, and standard IP cameras. Still the most widely deployed standard.

802.3at — PoE+

Doubles the power to 30W (25.5W at PD). Same 2-pair architecture. Covers dual-band APs, PTZ cameras, and video conferencing endpoints. Fully backward compatible with 802.3af — the PSE auto-negotiates the correct power level.

802.3bt — PoE++

The breakthrough: uses all 4 pairs to deliver up to 100W. Two tiers — Type 3 (60W) and Type 4 (100W). Powers Wi-Fi 6 APs, LED lighting, and even small displays. Cat6 cable is recommended to handle the extra heat.

A Comprehensive Guide to the Three Major PoE Standards: 802.3af / 802.3at / 802.3bt 2

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