Short answer
Yes. A PoE switch needs its own mains power supply, because it provides the power for every device plugged into it. The switch draws mains electricity, converts it, and sends it down the ethernet cables. Its total power budget must cover all connected cameras, access points and phones.
Updated 2026-09-21 · 3 min read
Internal or external power supply
Rack switches almost always have an internal power supply with a standard mains lead, and larger models can take two for redundancy. Small desktop PoE switches often use an external power brick — and on those, the brick's rating is what limits your PoE budget, so never swap it for a smaller one.
How to size the power budget
- List every powered device and its real draw in watts
- Add them up — this is your minimum budget
- Add about 25% headroom for devices added later
- Choose a switch whose PoE budget exceeds that figure
Put the switch on a UPS
Because everything downstream is powered by the switch, losing the switch means losing your cameras, Wi-Fi and phones at once. A small rack UPS keeps them running through short outages and protects the switch from spikes — this is the single most common gap we see in small comms rooms.
Related questions
- Can a PoE switch be powered over PoE itself?
- Some small 4 or 5-port switches can be, and they are useful at the end of a long run. Anything larger needs mains power.
- What happens if the power budget is exceeded?
- The switch stops powering lower-priority ports. Devices then drop off, usually intermittently, which is why a budget with headroom matters.
Hardware for this
The ranges below cover what this article describes, supplied in the UK with lead times confirmed before you commit.
