Gaining insights into PoE Standards and Wattage

Andy Chen

PoE (Power over Ethernet) technology revolutionizes the way power and data are transmitted over Ethernet cables. It enables Power Sourcing Equipment (PSE), such as a PoE switch, to deliver power and data simultaneously to Powered Devices (PD), including IP cameras and VoIP phones. This integration simplifies cabling installation, eliminates the need for separate power cables, and reduces overall costs.

To regulate the power delivery to PDs, the Institute of Electrical and Electronic Engineers (IEEE) has established various PoE standards, including IEEE 802.3af, 802.3at, and 802.3bt. These standards define the maximum power that PSEs can provide and the power requirements for PDs.

Let's delve into the details of these PoE standards and their associated wattage.

PoE Standards Introduction

PoE standards encompass three main types: IEEE 802.3af, IEEE 802.3at, and IEEE 802.3bt. These standards establish the minimum power that Power Sourcing Equipment (PSE) can provide and the maximum power that Powered Devices (PD) can receive.

Figure 1: IEEE 802.3af, IEEE 802.3at and IEEE 802.3bt Introduction

1. IEEE 802.3af (Standard PoE)

Operating within a voltage range of 44-57V and delivering a current of 10-350mA, IEEE 802.3af ensures a maximum power output of 15.4W per port. Due to power loss over Ethernet cables, the minimum guaranteed power available at the Powered Device (PD) is 12.95W per port. This standard is commonly used for devices like VoIP phones and sensors.

2. IEEE 802.3at (PoE+)

As an upgraded standard compatible with IEEE 802.3af, PoE+ operates with a supply voltage ranging from 50V to 57V and a supply current of 10-600mA. It provides up to 30W of power per port on Power Sourcing Equipment (PSE), ensuring a minimum power output of 25W per port. This standard is suitable for devices like wireless access points and video conferencing systems.

3. IEEE 802.3bt

IEEE 802.3bt is the latest PoE standard that introduces two types of power delivery - Type 3 and Type 4. These types increase the maximum PoE power by utilizing multiple pairs of Ethernet cables. In Type 3 and Type 4 modes, PSEs identify the PDs and allocate power based on their maximum power requirements, resulting in an enhanced power delivery system. This standard includes support for higher-speed Ethernet standards like 2.5GBASE-T, 5GBASE-T, and 10GBASE-T, unlike the previous standards limited to 1-Gbps. It is designed for demanding applications such as laptops and LED lighting.

a. Type 3 (PoE++)

Type 3, also known as PoE++, can deliver up to 60W per PoE port (with a minimum of 51W on each PD port). It is suitable for powering devices such as video conferencing system components.

b. Type 4 (Higher-Power PoE)

Type 4 offers a maximum power output of 100W per PoE port (with a minimum of 71W on each PD port). This level of power delivery is ideal for devices like laptops and TVs.

Both Type 3 and Type 4 modes of IEEE 802.3bt are backward compatible with IEEE 802.3af and IEEE 802.3at standards. The following table summarizes the specifications of the PoE standards, including PoE wattage:

Name IEEE Standard PD Min. Power Per Port PSE Max. Power Per Port Cable Category Power Over Pairs Released Time
PoE IEEE 802.3af 12.95W 15.4W Cat5e 2 pairs 2003
PoE+ IEEE 802.3at 25W 30W Cat5e 2 pairs 2009
PoE++ IEEE 802.3bt 51W 60W Cat5e 2 pairs class0-4,
4 pairs class5-6
PoE++ IEEE 802.3bt 71W 100W Cat5e 4 pairs class7-8 2018


Understanding PoE Wattage

As previously explained, IEEE 802.3af provides a maximum power output of 15.4W per port, while PoE+ (IEEE 802.3at) supports up to 30W. However, when connecting multiple devices to a single PoE/PoE+ switch, it becomes crucial to ensure that the combined power requirements of these devices do not exceed the maximum power wattage supported by the switch. This ensures that the switch can reliably provide sufficient power to all connected devices without overloading its capacity. Careful consideration and planning are necessary to avoid exceeding the switch's power limitations and maintain stable operation.

For example, let's take the LINOVISION POE-SW708GM-DC12V, a managed PoE++ switch with 8 RJ45 ports and 2 SFP ports. Compliant with IEEE 802.3af/at/bt standards, this switch has a total power budget of 240W. This means it can concurrently power 8 devices compliant with PoE+ standards (30W x 8 = 240). It can also support 8 devices compliant with PoE standards (15W x 8 = 120W).


However, there is no need for concern as modern network switches are designed to be intelligent. When a device is connected, the switch automatically detects whether it is compatible with PoE or PoE+. If the device requires a low power of 5W, the switch supplies exactly that amount. If the device demands a higher power of 20W, the switch adjusts accordingly. And if you connect a device without PoE capability, rest assured that the switch will provide data transmission only.

How Much PoE Wattages are Need?

The power needs of your devices depend on what you're connecting. Most devices, such as security cameras, IP phones and standard wireless APs, require no more than 30 watts.

However, certain devices, such as 802.11ac wireless access points with multiple USB ports and radios, may require over 30 watts for optimal performance. In such cases, PoE++ or PoH switches are the ideal solution. It's worth noting that some devices can adapt to lower power availability by using fewer radios or disabling certain features.

Linovision Managed Switches: Your PoE Solution

At Linovision, we offer a range of PoE/PoE+/PoE++ switches that comply with the PoE standards, providing enhanced security and improved capabilities. These switches are available in 4,5,8 and 48 port options. They support layer 2+ switching features like VLAN and offer advanced management options such as WEB, CLI, TELNET, and SNMP. FS PoE/PoE+ switches can power any 802.3af or 802.3at compliant device on the market, providing flexibility and security. The table below provides specifications for four of our PoE/PoE+/PoE++ switches:


Model PoE Standard Port Switch Capacity Power Budget Forwarding Rate AC/DC Power Supply
POE-SW708GM IEEE 802.3af/at/bt 8x RJ45 | 2x SFP 36 Gbps 240W 14.88 Mpps DC
POE-SW716GM-10G IEEE 802.3af/at 16x RJ45 | 4x SFP 112 Gbps 360W 83.3 Mpps DC
POE-SW328G-BT2000 IEEE 802.3af/at/bt 24x RJ45 | 4x SFP 56 Gbps 740W 41.7 Mpps DC/AC


It is essential to have a clear understanding of PoE standards and wattage to ensure effective device connections. By aligning your devices' power requirements with the appropriate PoE standard, you can ensure smooth and reliable operation. PoE technology simplifies complex cabling setups and offers flexibility in power delivery.