PoE in plain words: why you need it and how to choose a switch

Published 2026-11-03 · 5 min read · By the Alian Digital team

PoE lets you power an access point or camera over the same cable that carries the network. That means fewer wires and power you can back up in one place.

Why PoE

• No need for a socket by a ceiling access point or a camera on the facade.
• One power location: easy to add a UPS so the network and cameras keep working without electricity.
• Cleaner installation: one cable instead of two.

Standards

• 802.3af (PoE): up to 15.4 W per port, usually enough for most access points and simple cameras.
• 802.3at (PoE+): up to 30 W for more powerful points and PTZ cameras.
• 802.3bt (PoE++): up to 60 and 90 W for the most demanding devices.

How to calculate the budget

A switch has a total PoE budget (for example 120 W) and a per-port limit. Add the consumption of all devices and leave headroom. With many devices the budget runs out before the ports do.

Cable limits

An Ethernet cable works up to 100 metres. For PoE copper quality matters: cheap copper-clad aluminium (CCA) cables heat up and lose power, so buy pure copper.

When PoE is not needed

If a point stands next to a socket and you already have a non-PoE switch, a power adapter will do. But during renovation PoE wiring usually wins.