i appreciate that you're trying to explain this to me but tbh, you're not helping lol. the method I've been using has never failed me.
in fact, my method should have been enough to tell me that my 700watt ocz was going to blow up soon enough.
using my method that 700watts (@ 80% efficiency ) psu would only give me 560watts at peak. my system uses 596watts at 90%peak (100% peak is going to be higher). this in itself should have shown me that the 700watt psu was not going to last very long. 6 months later, my branded psu shat itself.
using your method, my psu would still be here working today. simply because it's output is higher than my requirements by over 100watts. but that's not the case. i have to RMA my psu because it failed. so, speaking from previous experience (building and repairing pc's for 10 years) i should have never bought the 700watt and went straight for an 850watt.
now, i might be wrong but at the end of the day, given my situation, my method should have warned me (at the point of purchase) the the 700watt was going to blow.