Get power consumption of a USB device

Take a look at this SuperUser Q&A titled: How do you check how much power a USB port can deliver?, specifically my answer.

lsusb -v

You can get the maximum power using lsusb -v, for example:

$ lsusb -v|egrep "^Bus|MaxPower"
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
    MaxPower                0mA
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
    MaxPower                0mA
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
    MaxPower                0mA
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
    MaxPower                0mA
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
    MaxPower                0mA
Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
    MaxPower                0mA
Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
    MaxPower                0mA
Bus 001 Device 003: ID 05e3:0608 Genesys Logic, Inc. USB-2.0 4-Port HUB
    MaxPower              100mA
Bus 003 Device 002: ID 046d:c517 Logitech, Inc. LX710 Cordless Desktop Laser
    MaxPower               98mA
Bus 001 Device 004: ID 04a9:1069 Canon, Inc. S820
    MaxPower                2mA
Bus 001 Device 005: ID 05ac:120a Apple, Inc. iPod Nano
    MaxPower              500mA
    MaxPower              500mA

You could also have a look at usb-devices:

$ usb-devices | grep 'Product=\|MxPwr'
S:  Product=EHCI Host Controller
C:  #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=0mA
C:  #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=0mA
S:  Product=EHCI Host Controller
C:  #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=0mA
C:  #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=0mA
S:  Product=USB Keykoard
C:  #Ifs= 2 Cfg#= 1 Atr=a0 MxPwr=98mA
S:  Product=USB Receiver
C:  #Ifs= 2 Cfg#= 1 Atr=a0 MxPwr=98mA
S:  Product=DW375 Bluetooth Module
C:  #Ifs= 4 Cfg#= 1 Atr=e0 MxPwr=100mA
S:  Product=5880
C:  #Ifs= 2 Cfg#= 0 Atr=c0 MxPwr=100mA

There's a bMaxPower file in the device's sysfs folder. But I do not think it is going to be very useful. You'll be able to find that the device "requested" 500mA just to comply with the standard but not the actual current drain.