What is the Difference Between PoE and PoE+?

Posted by Cablesys on Oct 17th 2018

Network cabling systems that are PoE (Power over Ethernet) or PoE+ compliant allow electric power and data to pass over twisted pair Ethernet cabling. Understanding the differences between them can help in deciding which system to choose.

IEEE 802.3af is the original PoE standard. It specifies a maximum of 15.4W of DC power delivered to each network device. IEEE 802.3at, also known as PoE+, specifies up to 30.0W of DC power.

PoE has a maximum of 15.4 W of DC power. PoE+ has a maximum of 30.0 W of DC power.

Comparison of PoE Parameters

Property 802.3af (802.3at Type 1) "PoE" 802.3at Type 2 "PoE+"
Power available at PD 12.95 W 25.50 W
Maximum power delivered by PSE 15.40 W 30.0 W
Voltage range (at PSE) 44.0–57.0 V 50.0–57.0 V
Voltage range (at PD) 37.0–57.0 V 42.5–57.0 V
Maximum current I max 350 mA 600 mA
Maximum cable resistance per pairset 20 Ω 12.5 Ω
Power management Three power class levels negotiated by signature Four power class levels negotiated by signature or 0.1 W steps negotiated by LLDP
Derating of maximum cable ambient operating temperature None 5°C (9°F) with one mode (two pairs) active
Supported cabling Category 3 and Category 5 Category 5
Supported modes Mode A (endspan), Mode B (midspan) Mode A, Mode B

The types of devices that will be connected to the network and the amount of power they will require must be considered when evaluating a PoE solution. Below are some examples.

PoE applications include VOIP Phones, WiFi, and Security Cameras. PoE+ applications include Pan/Tilt/Zoom Cameras, Video IP Phones, and Alarm Systems.

Another factor to consider is changes in technology. As more and newer devices are added to the network, higher power levels may be drawn. An existing PoE network might not be able to keep up and need to be upgraded. PoE+ will be able to support them.

Price is also a factor. Even though PoE+ cost more, there will be less worry or pain from upgrading the entire PoE system.

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