It doesn't. If your socket can't deliver 1600W and the PSU actually tries to draw its peak power then you're shit out of luck and you're gonna either trigger the breaker (the good ending) or if the bottleneck is bad wiring and not the design limit of the circuit enforced by a breaker then it's a toss up between the voltage sagging at the PSU input enough to drop it below the minimum operating voltage and make it shut down or being able to deliver juuust enough power to keep the PSU running and instead building heat at the bad wiring joint until you get a house fire.