well, cpu and motherboard, lets say a good
150 watts tops. gpu roughly
120 watts under normal gaming modes. no overclocking. add a bit more for other stuff like hdds etc
thats right up there with the above review's limits where the psu starts crapping out. if your computer was going out before and doesnt anymore,again dont use the gpu but for desktop and email, then it was the psu
edit its well worth it to get something like a kill a watt, best 20 bucks youll ever spend. not only it tells you how much juice is being pulled from the wall, but you can also troubleshoot.
for exemple, lets say your computer pulls 300 watts at the wall, nothing changes and one day it pulls 350? somethings up. i do check on my puters, and its really easy. there are also power bars with this function, a bit expensive though.