How this is worked out
- Cameras are counted against the recorder sizes actually sold: 4, 8, 16, 32 and 64 channel.
- Spare ports are added so the system can grow and so one dead port does not mean a new switch. 25% is a sensible allowance.
- The power budget is the total camera watts plus a 20% headroom, because PoE loses a little in the cable and a camera draws more with IR on and the heater running.
- PoE standards: 802.3af gives 15.4 W at the port, 802.3at (PoE+) 30 W, 802.3bt (PoE++) 60–90 W. The figure that matters is what the port delivers, not what the camera uses.
- A switch quoted as "16 port PoE, 150 W" cannot run 16 cameras at 12 W each. The port count and the power budget are two separate limits, and both must pass.
An estimate for planning, not a design document. Site conditions change the answer — send it to us and we will confirm it free of charge.