The value of PoE shows up most clearly on mid-size and large projects: camera positions no longer need a separate mains feed, so installation effort, material cost and ongoing maintenance all come down. But PoE is not simply plug and play — a miscalculated power budget tends to surface during commissioning.

Three things need working out in advance. The first is the power budget: the switch's total capacity must have headroom, because PTZ domes and heated outdoor models draw noticeably more at start-up than their nominal rating. The second is cable specification: Cat5e and Cat6 differ in long-run performance and noise immunity, and copper-clad aluminium conductors are far more likely to cause trouble under full load or high temperature. The third is distance: beyond 100 metres you need switch cascading or extenders, not just a longer cable.

For outdoor positions, add surge and lightning protection on the switch side and keep power runs away from high-voltage trays. On the drawing these are a few lines of note, yet they directly shape the failure rate during summer heat and the thunderstorm season.