It appears as though all 8 port provide PoE on the ASR-920-12SZ-IM model. Look under the "Prerequisites for PoE" section of this link for a starting point:
http://www.cisco.com/c/en/us/td/docs/routers/asr920/hardware/chassis/guide/ASR920-Chassis-SW/PoE.html
"Prerequisites for PoE
- -Cisco ASR-920-12SZ-IM Aggregation Services Router supports multiple variants of power supplies. When using the AC power supplies, approximately 180 watts is used for PoE functionality, which can be shared by all eight available copper Ethernet ports.
- -PoE is applicable only on the following ports: Gi0/0/0 to Gi 0/0/7
- -When using DC power supplies, PoE is supported only if the input feed to the power-supply is 48 volts
- Restrictions for PoE
- -Configuring a port as a static port pre-provisions power for that port. This power is deducted from the central power pool. It is, therefore, advisable to configure a port as an auto port.
- -PoE does not support interface modules (IMs).
- -The system allocates 180 W of static power. However, if a component or device tries to draw power over 180 W, the Cisco ASR-920-12SZ-IM Router silently reloads."
