It might have something to do with the pure sinewave thing, not sure. I don't understand it completely, and I actually don't have a 1500W source to put it to the real test, but considering the price difference, this damn well BETTER be 1500W, LOL! I can only draw about 980W from it peak, which is dangerously close to tapping out my 1000W EVGA PSU. I think if I *really* uncork PBO, max out all the limits, I could hit 1000W.
But who knows, if I ever get a new GPU (6900XT is on order), then everything changes. My 2080ti gets the boot out of the gaming rig, so I can move that into the workstation, and ditch the dual 1080ti's completely and not need all this power.