By the SightShield team · · 3 min read
One cable instead of two
Power over Ethernet (PoE) sends electrical power and network data down the same Ethernet cable. For IP cameras, that means a single Cat6 cable from the switch or NVR to each camera — no separate power adaptor or power point at the camera. It makes installation neater, cheaper and more reliable, and it is why most new business CCTV systems are IP and PoE.
Where the power comes from
- A PoE NVR — many NVRs have built-in PoE ports (commonly 4, 8 or 16) so cameras plug straight in.
- A PoE switch — a network switch that supplies power on its ports, used for larger systems or when cameras are far from the NVR.
- A PoE injector — a small adaptor that adds power to one cable, handy for a single camera on a normal switch.
The PoE standards
| Standard | Common name | Power at the switch port | Power available at the device |
|---|---|---|---|
| IEEE 802.3af | PoE | up to 15.4 W | about 12.95 W |
| IEEE 802.3at | PoE+ | up to 30 W | about 25.5 W |
| IEEE 802.3bt Type 3 | PoE++ / 4PPoE | up to 60 W | about 51 W |
| IEEE 802.3bt Type 4 | PoE++ / 4PPoE | up to 90 W | about 71 W |
Which cameras need what
Most fixed dome, bullet and turret IP cameras run comfortably on standard PoE. Cameras with strong IR, built-in white lights, heaters, or motorised zoom may need PoE+. PTZ cameras with long-range IR often need PoE+ or a higher class, or their own power supply. Always check the camera’s maximum power draw on its datasheet.
Power budget: the common mistake
A PoE switch has a total power budget as well as a per-port limit. A 16-port switch might offer only around 120–250 W in total, depending on the model. Sixteen cameras drawing 8 W each need 128 W — fine. But add IR at night (when power draw peaks) and a couple of PTZs, and the budget can run out. When that happens, cameras reboot at night, exactly when you need them. We size switches for the night-time peak with spare headroom.
Choosing a PoE Switch for CCTV →The 100-metre rule
Ethernet, and therefore PoE, is specified for up to 100 metres of cable between the switch and the camera, including patch cords. Beyond that you need a switch in between (which itself needs power), a PoE extender, or fibre-optic cable with media converters. Long runs across factory compounds and campuses usually use fibre between buildings and PoE switches in each building.
Cable matters
- Use solid pure-copper Cat6 cable. Cheap copper-clad aluminium (CCA) cable heats up and drops voltage under PoE, causing cameras to reboot.
- Use outdoor-rated cable or conduit for outside runs, and protect cables entering camera junction boxes from water.
- Terminate and test every run; a single bad crimp can stop a camera from powering on.
- Add surge protection on long outdoor runs, especially on poles and rooftops in lightning-prone areas.
Power backup
Because cameras are powered from the switch or NVR, putting those on an inverter or UPS keeps every camera running through power cuts. That is simpler than backing up a separate power supply at each camera.
IP CCTV and network installation →Quick answers
How far can a PoE camera be from the switch?+
Up to 100 metres of Ethernet cable. For longer distances use an intermediate switch, a PoE extender or fibre-optic cable.
Can a normal network switch power a camera?+
No, only a PoE switch, a PoE NVR or a PoE injector supplies power over the cable.
Why do my PoE cameras reboot at night?+
Night-time IR increases power draw. If the switch’s total PoE budget is exceeded, or the cable is poor quality, cameras can drop out. A larger switch budget or better cable usually fixes it.