When adding access points, cameras, phones, or other powered network devices, I think PoE capacity is something that is easy to overlook.
I usually look at the total number of devices first and then check how much power each device requires. The switch's overall PoE budget is important, but the maximum power available on an individual port also needs to be considered.
It is also worth leaving some spare capacity rather than sizing the switch exactly to the current requirements. A network may start with a few access points or other PoE devices and gradually add more over time.
Another thing I would check is whether the switch supports the PoE standard required by the devices. Using the wrong PoE capability can create problems even when the port count looks sufficient.
For those who have managed PoE networks, how much spare power capacity do you normally leave when planning a new switch?
I have also been comparing different networking and PoE equipment options for reference through wavonline.