A switch’s PoE budget is the total power it can deliver to powered devices. That total budget is separate from the amount any one port can provide.
List every powered device
Add access points, cameras, phones, intercoms, access-control equipment, sensors and PoE-powered downstream devices.
Use conservative wattage
For design, use manufacturer maximum power draw or a measured worst-case value. Designing from idle wattage can create failures when radios, heaters, IR illuminators or other features increase consumption.
Check standards and ports
A large total budget does not guarantee that a particular port supports the power standard required by a high-draw device.
Keep headroom
Reserve makes expansion and replacements easier and reduces reliance on every device remaining below its stated maximum.