PoE Standards and Power Levels
Power over Ethernet (PoE) delivers DC power to network devices over the same CAT cable used for data, eliminating the need for separate power supplies and wall outlets at each device location. IEEE 802.3af (PoE, 2003) delivers up to 15.4W per port at the switch, with 12.95W available at the powered device (PD) after cable loss. IEEE 802.3at (PoE+, 2009) doubles this to 30W at the switch and 25.5W at the PD. IEEE 802.3bt (PoE++, 2018) added Type 3 (60W at switch / 51W at PD) and Type 4 (90W at switch / 71.3W at PD) using all four pairs of the CAT cable for power delivery. NFPA 70 (NEC) Article 725 covers Class 2 power circuits relevant to PoE installations.