There are 3 standards for PoE products including IEEE 802.3af, IEEE 802.3at and IEEE 802.3bt.
These PoE standard specific the maximum power output from PSE(power source equipment) as well as the maximum power budget to the PD(powered device). The below is the breakdown list.
|Standard||PD min. Power Per Port||PSE Max. Power Per Port|
PSE and PD are compatible with same specification would be able to transport the maximum power budget. The higher standard product is usually backward compatible with lower standard one. For example, if PD is IEEE 802.3at PTZ camera and require 25W power budget, both IEEE 802.3at and IEEE802.3 bt PoE injector are capable of supply enough power while IEEE 802.3af injector can’t make the PTZ camera work as the power budget is restricted to 12.95W. The actual power budget depends on the lowest standard one in the system.