“How many cameras can this switch run?” is the most common question we get about PoE — and the honest answer is almost never a port count. A PoE switch has two limits, and both matter: the PoE budget (total watts it can deliver) and the number of PoE ports (how many devices it can feed). Mix them up and you’ll buy a switch that’s either half-empty or silently dropping cameras at night.
The 30-second version
- Count watts, not ports. Every camera has a max draw; the sum decides the switch.
- A switch’s PoE budget is its real capacity — many 8-port switches only power 4 ports anyway.
- Size to ~80% of budget, not 100%. IR LEDs, heaters, and surges all draw above the typical number.
- A camera that doesn’t get enough power doesn’t fail loudly — it reboots, drops frames, or dies at night.
The two numbers on every datasheet
1. PoE budget (total watts). This is the ceiling for everything plugged in. UniFi’s USW-Lite-8-PoE, for example, has a 52W budget — and only 4 of its 8 ports deliver power at all. That’s the trap: people read “8-port PoE switch” and plan eight cameras. The budget and the powered-port count are the specs that actually decide.
2. Per-port standard. 802.3af (PoE) tops out at ~15W per port; 802.3at (PoE+) at ~30W; 802.3bt (PoE++) goes higher for the big stuff. Most security cameras are af or at, but check the camera’s datasheet — if it asks for at and your switch only delivers af, the camera may power up and then reboot when its IR or heater kicks in.
What cameras actually draw
Real UniFi Protect numbers, roughly:
- Fixed indoor/outdoor cams (G4/G5 class): 4–7W typical, spikes higher with IR on at night.
- Domes and turrets with IR: 6–9W.
- Pro / AI / PTZ models: 10–13W+, some higher — these are where PoE+ ports matter.
Rule: size on the max draw from the datasheet, not the typical number. Night mode is not optional load — it’s when cameras matter most.
The sizing math
Sum the max draws, add headroom, then pick a switch:
- List every camera and its max draw from the datasheet.
- Sum them. Eight 6W cameras = 48W.
- Add 20–25% headroom → 48W × 1.25 ≈ 60W. That’s your minimum budget.
- Check the port count — you need eight PoE ports, not eight total ports.
That example lands on a switch with ~60W+ budget and 8+ powered ports, not the Lite-8-PoE (52W, 4 powered ports) that “8 ports” sounds like it should handle.
Why headroom is non-negotiable
Nobody plans for the real-world loads: IR LED arrays drawing more in winter, a camera with a fan or heater, a future camera added “real quick” to a free port. Running a switch at 100% of budget also means the first power surge during a firmware reboot cycle can brown out cameras you thought were fine. Twenty percent of headroom is cheap insurance — the alternative is a camera that dies at 2 AM and nobody notices until the morning after something happened.
Injectors vs. switches
One or two cameras on an existing non-PoE network? An injector is fine. Once you’re past two, or cameras are spread across the building, a PoE switch pays for itself in clean cabling, one UPS, and one place to check link status. Daisy-chaining injectors behind a rack is how you get the “silently stopped recording” failure we see in audits — it’s the same mistake as an undersized switch, just with extra failure points.
The takeaway
Read the budget line, not the port count. Sum max draws, add 25%, and make sure the powered-port count matches your camera plan — today and next year. That’s the whole discipline, and it takes five minutes with a datasheet.
Not sure what your current switching actually delivers? The 60-second Network Health Check flags undersized PoE budgets — it’s one of the six things we score.
Need the install done right? We design and deploy UniFi networks across Chicago — see how we scope it, or ask about a long-term partnership so the network stays sized as you grow. Related reading: how much camera footage to keep and the retention math behind it.