The IEEE 802.3af (PoE) standard supports the delivery of power over Ethernet up to 15.4W per port that may be used to deliver power to a variety of devices. However, only 12.95W is assured to be available at the powered device as some power is dissipated in the cable as overhead.
The IEEE 802.3at (PoE+) standard supports up to 25.5W of power on the ports, allowing devices that require more than 15.4W to power on when connected to the PoE+ ports.
https://documentation.meraki.com/MS/Other_Topics/IEEE_802.3af_(PoE)_and_IEEE_802.3at_(PoE_)_Support_on_Cisco_Meraki_MS_Switches
