WAX214 poe voltage/wattage

You don't have to care about the exact voltage. IEEE standard PoE does a handshake between the PSE (power source device, e.g. the POE switch) and the PD (powered device, e.g. the AP here). The PoE standard does define the voltage, does define when the AP can be powered, .... and much more.

The WAX214 is a PoE device, requiring IEEE 802.3af (802.3at Type 1) power, to be exact it's a 1 Gigabit Ethernet device, it requires the max what 802.3af can supply (PoE Class 3), this is guaranteed 12.95 W at the PD, and 15.4 W at the PSE (to overcome the cable losses). I admit, Netgear is not clear on the related data sheets as of writing.

The WAX218 is a PoE+ device, requiring IEEE 802.3at Type 2 power, to be exact it's a 2.5 Gigabit Ethernet device (a 1 GbE would lower the maximum available wireless bandwidth), it requires the max what 802.3at can supply (PoE Class 4), this is 25.5 W at the PD, and 30 W at the PSE (to overcome cable losses again). For what it's worth,  IEEE 802.3at PoE+ is backward compatible to the 802.3af PoE. 

The details and requirements are well documented on the WAX214/WAX218 User Manual however. The POE switches always list the available PoE power budget. Not all models can offer the full power to all the powered ports.

Worth noting, there exist also 802.3bt Type 3 (51 W at the PD, 60 W at the PSE) and 802.3bt Type 4 (71.3 W at the PD, 100 W at the PSE). Also these PSE (PoE switches) are always backward compatible.

If we take the GS108LP 8-Port Gigabit Ethernet PoE+ Unmanaged Switch with FlexPoE (60W) for example, you find eight PoE+ ports, but a power budget of max 60 W. This does allow to operate three WAX214 (PoE, 3x IEEE 802.3af (802.3at Type 1)15.4 W) on the secure side, or max. two WAX218 PoE+ requiring 2x 30W IEEE 802.3at Type 2.

For exact voltage specs - the standard does make it secure and safe for the user - see https://en.wikipedia.org/wiki/Power_over_Ethernet - you don't have to care about it. Be aware that there are vendors offering non-IEEE misleadingly designated PoE (sometimes named passive PoE) systems. If you see "PoE" voltages listed like 24 V, 48 V or the like, be aware these are not IEEE standards, but proprietary systems.