What does PoE stand for?
PoE stands for Power over Ethernet. Delivers DC power over the same twisted-pair cable as Ethernet data, so access points, IP phones and cameras need no separate outlet. Standards: 802.3af (15.4 W), 802.3at PoE+ (30 W), 802.3bt (60 or 100 W). Power comes from a PoE switch or an injector.
PoE delivers electrical power to a device over the same twisted-pair cable that carries its network data. Access points, IP phones and cameras can then be installed where there is no power socket. The power comes from a PoE switch or, for a single device, from an injector placed between an ordinary switch and the device. The original standard, 802.3af, supplies up to 15.4 watts per port; 802.3at, known as PoE+, up to 30 watts; 802.3bt up to 90 watts. A switch also has a total power budget shared by all its ports.
PoE in practice: an example
A technician mounts a new access point on a ceiling and connects it to an older PoE switch. The access point starts but runs with reduced radio power. It needs 25 watts and the port delivers at most 15.4. Moving it to a PoE+ port, or adding a PoE+ injector, gives it full power.
What PoE is confused with
PoE vs PoE+: what is the difference?
PoE is the original 802.3af standard at up to 15.4 watts per port. PoE+ is 802.3at at up to 30 watts. A device that needs PoE+ may start on a PoE port but will not run at full capability.
PoE vs power injector: what is the difference?
A PoE switch supplies power from its own ports. An injector adds power to one cable when the switch has no PoE.
Which exams cover PoE?
PoE is on the official CompTIA acronym list for two of the four exams covered here.
- Network+ N10-009: 5.0 (Network Troubleshooting).
- A+ 220-1201 and 220-1202: 220-1201 2.0 (Networking).
Each number is a CompTIA exam objective and the name in brackets is its domain. The exam puts the term in a scenario; it does not ask you to recite the expansion.
Check yourself: two practice questions
Written by CertSprint for this page. They are not taken from any exam.
1. A camera must be installed on an outside wall with no power socket nearby. Which technology avoids running a separate power line?
- PoE
- A crossover cable
- Port mirroring
- A fibre patch lead
Show the answer
A. PoE. PoE carries power and data on one twisted-pair cable. Fibre and crossover cables carry no power to the device.
2. A switch has no PoE ports and one IP phone needs power over its cable. What is the simplest fix?
- Replace all the cabling with fibre
- Insert a PoE injector between the switch and the phone
- Enable jumbo frames
- Change the phone's VLAN
Show the answer
B. Insert a PoE injector between the switch and the phone. An injector adds power to a single cable run without replacing the switch.
Sources: IEEE 802.3bt-2018: Power over Ethernet over 4 pairs; NIST glossary: Power over Ethernet. The acronym and its expansion come from CompTIA's official acronym lists, linked from each exam glossary above. The explanation, example and questions are CertSprint's own, checked against these sources on 11 November 2026.