My ups is a 750VA/375Watt capacity unit. All I have plugged in is my cpu, whis has a 550 watt psu. Under normal conditions it works fine, but as soon as I play a power hog likg grid, it goes crazy. Apparently, grid uses more wattage than the ups allows, therefore it won't be able to handle it. For some strange reason, I always thought that once it was plugged in the outlet, then it didn't matter.
I wasted money on a forza when I could have gotten an apc for just a little more.