A:
This may not be a good place to ask, APC tech support may have better answer.
How I know when its over load? Well, there is a digital gauge and you will see the loading percentage, if is over load it will beep. Most common beep for me is when a user makes a laserjet printer to print. So, it is hard more me to keep track of wats and volts, when a sudden need for power happens, it will over load, and it will go back to normal when printing is done. So, it is better to do a live test if I were you.