Two-pair and four-pair Ethernet
The IEEE 802.3af (year 2003) PoE standard provides up to 15.4W of DC power (minimum 44 V DC and 350 mA) on each port. It ensures that only 12.95W is available on the powered device, as some power disappears in the cable.
The IEEE 802.3at (year 2009) PoE standard, also known as PoE+ or PoE plus, provides up to 25.5 W of power for Type 2 devices. The 2009 standard prohibits a powered device from using all four pairs for power. The 2009 standard prohibits a powered device from using all four pairs for power. Both standards have since been included in the IEEE 802.3-2012 publication.
The IEEE 802.3bt (Year 2018) standard further extends the power capabilities of 802.3at. This standard is also known as PoE++, HiPoE or 4PPoE. The standard introduces two additional power types: up to 51 W delivered power (Type 3) and up to 71.3 W delivered power (Type 4). Each pair of twisted pairs must handle a current of up to 600 mA (Type 3) or 960 mA (Type 4). In addition, there is support for 2.5GBASE-T, 5GBASE-T and 10GBASE-T. This development opens the door to new applications and expands the use of applications such as high-performance wireless access points and surveillance cameras.
Single-pair Ethernet
The IEEE 802.3bu amendment (year 2016) introduced single-pair Power over Data Lines (PoDL) for the 100BASE-T1 and 1000BASE-T1 single-pair Ethernet standards, intended for automotive and industrial applications. With the two-pair or four-pair standards, the same supply voltage is applied to each conductor of the pair, so there is no differential voltage within each pair other than the voltage representing the transmitted data. In single-core Ethernet, the power is transmitted in parallel with the data. PoDL initially defined ten power classes, ranging from 0.5 to 50 W (at PD).
PoDL was then added to the single-pair variants 10BASE-T1, 2.5GBASE-T1, 5GBASE-T1 and 10GBASE-T1 and, as of 2021, comprises a total of 15 power classes with additional intermediate voltage and power levels.
| PoE standard | Power | Power | |
| IEEE 802.3af | PoE standard | 15.4 W | |
| IEEE 802.3at | PoE+ or PoE plus | 25.5 W | |
| IEEE 802.3bt | PoE++ or 4PPoE | 51 W | 71.3 W |
| IEEE 802.3bu | 0.5 to 50 W |