I am trying to figure out what a good uninterpretable power supply would be for my system but I am not sure if the one I am looking at will work. That is to say, I am looking at a "Tripp Lite INTERNET550U Internet Office 550VA Compact UPS" which is 550VA/300W power capacity.
On the other hand I have a gaming rig that uses a 550w(computer) power supply powering a 9800GT graphics card, though I understand it only needs 400? Needless to say I am not sure if this will work or not, to clarify the purpose of this purchase would be to keep the computer running 2-3 minutes in the event of a power problem so that it could be shut down, not to play anything.
I don't really know if it is even relevant what computer power supply I am using, but please let me know if this will work and if not, then perhaps help me in the right direction. Thank you. 
Size your UPS based on you power supply, even tho you do not drive it that hard.
My UPS is 450 watts and will last about 65 minutes, at full load, Manuf Specs.
But to really answer your question, the 300w would probably power your system for at least 15 minutes.
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