What Are PoE Standards and How Do They Differ?

Power over Ethernet (PoE) allows a single Ethernet cable to deliver both power and data, reducing cable clutter while enabling flexible device placement for IP cameras, access points, VoIP phones, and more. However, not all PoE is the same. The IEEE defines different PoE standards—802.3af (PoE), 802.3at (PoE+), and 802.3bt (PoE++)—each with distinct power capabilities. Understanding these differences helps you design a scalable, efficient network ready for current and future devices.

What Is Power over Ethernet (PoE)?

PoE enables network devices to receive power and data over a single Ethernet cable by using a PoE switch or a combination of a standard switch with a PoE injector or splitter. The power sourcing equipment (PSE) delivers electricity to the powered device (PD), simplifying installation and reducing costs.

If you need a foundational understanding, see our What is PoE? What is PoE+? PoE vs. PoE+ guide.

PoE Standards Explained: 802.3af vs 802.3at vs 802.3bt

802.3af (PoE)

• Introduced: 2003 (PoE Type 1)
• Max Power at PSE: 15.4W
• Power at PD: 12.95W
• Pairs Used: 2
• Typical Devices: VoIP phones, entry-level IP cameras, basic wireless access points

802.3at (PoE+)

• Introduced: 2009 (PoE Type 2)
• Max Power at PSE: 30W
• Power at PD: 25.5W
• Pairs Used: 2
• Typical Devices: Advanced APs, PTZ cameras, video IP phones

802.3bt (PoE++)

Introduced in 2018, 802.3bt (PoE++) expands power delivery by using all four cable pairs.

• Type 3 (UPOE): Up to 60W at PSE, 51W at PD. Used for multi-radio APs, advanced PTZ cameras, video conferencing devices.
• Type 4 (UPOE+): Up to 90-100W at PSE, 70-71W at PD. Supports laptops, thin clients, and LED displays.

PoE Standards Comparison Table

Choosing the Right PoE Standard

When selecting a PoE switch, consider:

• Device Power Needs: Check the wattage required by your devices. Advanced APs or PTZ cameras may require PoE+ or PoE++.
• Cable Length: Longer cables increase voltage drop; plan for higher standards if needed.
• Switch Power Budget: Ensure your switch can handle the total wattage across all ports.
• Future-Proofing: Investing in PoE+ or PoE++ helps support newer, power-hungry devices.

For a detailed step-by-step guide on selecting the ideal PoE switch for your network requirements, check out our article How to Choose the Right PoE Switch for Your Network.

Benefits of PoE Switches

• Cost Savings: No need for separate electrical wiring.
• Simplified Deployment: Power devices in locations without nearby outlets.
• Centralized Power Management: Often backed by UPS for power redundancy.
• Flexibility & Scalability: Easy to expand networks without electrical rework.

Frequently Asked Questions

Q1: What devices typically require PoE++?

High-power devices like multi-radio access points, advanced PTZ cameras, thin clients, and some displays may require PoE++ (802.3bt) to operate efficiently.

Q2: Can I use a PoE switch with non-PoE devices?

Yes, a PoE switch can connect to non-PoE devices, but these devices will only receive data, not power, unless you use a PoE splitter.

Q3: Do I need special cables for PoE?

802.3af can use Cat3 or better, while 802.3at/802.3bt require Cat5 or better. Using Cat5e/Cat6 is recommended for better performance and lower voltage drop.

Q4: How far can PoE transmit power?

Standard PoE supports up to 100 meters (328 feet). For longer runs, PoE extenders may be required.