Hi Tayzar,
To add on, there are few different power rated PSU's available for the chassis.
So it would all depend on the PSU rating you are using in the chassis. As my colleague has provided a command in the previous update, it would help you determine the power used and available power in redundancy.
There are quite a few caveats you need to consider on this and the Extreme Networks BlackDiamond 8800 Series Switch Hardware Installation Guide gives you good insight into you request.
http://documentation.extremenetworks.com/blackdiamond8800/downloads/8000_Series_Hardware_Install_Gui...
Thanks,