Size a PoE switch on its power budget in watts, not on its port count. An eight-port switch with a 110W budget will not run eight cameras that want 15W each — the maths says 120W, and the switch will start dropping devices.
Port count tells you how many things you can plug in. Power budget tells you how many you can actually run. They are not the same number, and the box always shouts the first one.
This is the single most common CCTV specification error we see at the counter, and it doesn't show up on day one. It shows up on a cold night when the infrared kicks in on every camera at once and the whole system starts rebooting.
1. What PoE actually does
Power over Ethernet sends data and power down the same network cable. One cable to each camera. No socket at the camera end, no separate power supply on a pole or under a soffit.
For CCTV that's transformative — it's the difference between running one cable to a corner of a building and running two, one of which needs an electrician.
The switch is what injects the power. Cameras that support PoE simply take it from the cable.
2. Power budget — the number to buy on
Every PoE switch has a total wattage it can deliver across all ports at once. That's the budget.
Add up what your devices draw, then leave headroom. Cameras draw their peak, not their idle, when infrared illuminators come on at night — which is precisely when they all do it together.
Trade Tip: size the budget on peak draw plus at least 25%, and take the peak figure from each camera's own datasheet rather than a rule of thumb. A system that runs perfectly in daylight and drops cameras after dark is almost always a switch at its power limit, not a faulty camera. The symptom looks like the cameras; the cause is the switch.
The Ruijie RG-ES110D-P is an 8-port PoE+ desktop switch with a 110W PoE budget and 2 x 1Gb uplinks. That budget is the figure to plan against — not the eight ports.
3. PoE, PoE+ and Hi-PoE
Three standards, and they are not interchangeable.
- PoE — the original. Fine for fixed bullet and dome cameras and access points.
- PoE+ — more power per port. What most modern IP cameras with infrared want.
- Hi-PoE — higher still. PTZ cameras, heated housings, anything with a motor.
A PoE+ switch runs a PoE device happily — the device only takes what it needs. The reverse is not true. Put a Hi-PoE camera on a plain PoE port and it either won't start or will misbehave under load.
The Ruijie RG-ES205GC-P is a 5-port gigabit cloud-managed PoE+ switch with a 54W PoE budget — a sensible size for a domestic four-camera system with room to grow. For a bigger site, the RG-ES226GC-P is a 26-port gigabit smart PoE switch with a 370W budget.
Where you need Hi-PoE specifically, the DS-3E0505HP-E is a 5-port gigabit unmanaged Hi-PoE switch with a 60W budget.
4. The 100 metre rule
Ethernet — data and PoE alike — runs to 100 metres from switch to device. That's the standard, and it's not a soft limit you can push with better cable.
It's also 100 metres of cable, not 100 metres as the crow flies. Up a wall, across a loft, along a soffit and back down adds up faster than people expect. Measure the route, not the map.
Trade Tip: if you're over 100m, don't chain cheap switches to bridge the gap — every hop is another thing to fail in a loft you'll never want to visit. Either bring the switch closer to the cameras and run one longer uplink back, or use fibre for the long leg. Putting the switch in the middle of the run is nearly always the cheaper and more reliable answer.
5. Switch or injector?
A PoE injector adds power to a single non-PoE link. One device, one injector, one plug socket.
A PoE switch powers everything from one box, on one plug, in one place.
For one camera an injector is fine and cheap. For three or more, an injector-per-camera means three plug sockets, three power bricks and three things to fail. Buy the switch.
6. Cable, briefly
PoE runs happily on Cat5e for most CCTV work. Cat6 gives more headroom on longer runs and higher-bandwidth cameras.
What matters more than the category is that it's solid copper, not copper-clad aluminium. CCA cable is cheaper, is sold widely, and is a genuinely poor choice for PoE — it has higher resistance, so it wastes power as heat over the run and gives you voltage drop exactly where you can least afford it.
Our Cat5 vs Cat6 guide goes into which to pull.
PoE switch quick-reference
| System size | Look for | Watch |
|---|---|---|
| 1 camera | Injector | Needs a socket at the injector |
| 2–4 cameras | 5-port PoE+, ~54W | Leave a spare port |
| 5–8 cameras | 8-port PoE+, ~110W | Budget, not port count |
| Large or multi-building | 24-port+, 370W class | Uplink and heat |
| PTZ or heated housing | Hi-PoE | PoE+ may not start it |
Expert Help in the West Midlands
We've been on Villa Road in Handsworth since 1975, and the counter is open to installers and homeowners alike.
Bring the camera model numbers and a rough idea of cable runs. We'll add up the real power draw from the datasheets rather than a rule of thumb, and tell you the budget you need — including whether you're about to cross 100 metres without realising.
Frequently asked questions
How many cameras can a PoE switch run?
It depends on the power budget, not the port count. Add up each camera's peak draw from its datasheet and add 25% headroom. A 110W switch runs roughly six 15W cameras comfortably, not eight — even though it has eight ports.
How far can PoE run?
100 metres of cable from switch to device. That's total cable length along the actual route, including vertical runs, not straight-line distance. Beyond that, move the switch closer or use fibre for the long leg.
Do I need PoE+ or will PoE do?
Most modern IP cameras with infrared want PoE+. Plain PoE suits fixed cameras and access points. PTZ cameras and heated housings usually need Hi-PoE. A higher standard runs a lower-rated device safely; the reverse does not work.