You can get power consumption information of your cisco router with show environment command.

This is output of my cisco 3945 router

Border#show environment
SYSTEM POWER SUPPLY STATUS
==========================
Internal Power Supply 1 Type: AC
Internal Power Supply 1 12V Output Status: Normal

Internal Power Supply 2 Type: Absent

SYSTEM FAN STATUS
=================
Fan 1 OK, Low speed setting
Fan 2 OK, Low speed setting
Fan 3 OK, Low speed setting
Fan 4 OK, Low speed setting
Fan 5 OK, Low speed setting

SYSTEM TEMPERATURE STATUS
=========================
Intake Left temperature: 17 Celsius, Normal
Intake Right temperature: 16 Celsius, Normal
Exhaust Right temperature: 17 Celsius, Normal
Exhaust Left temperature: 19 Celsius, Normal
CPU temperature: 50 Celsius, Normal
Power Supply Unit 1 temperature: 19 Celsius, Normal

REAL TIME CLOCK BATTERY STATUS
==============================
Battery OK (checked at power up)

SYSTEM POWER
===============
Motherboard Components Power consumption = 95.5 W
Total System Power consumption is: 95.5 W

Environmental information last updated 00:00:23 ago


As you see the Total System Power consumption is: 95.5 W