I've been making exactly the same graphs on a dutch forum! One final step to help people pick a power supply is to divide the power lost through the purchase price of a psu so you get power lost per dollar you spend on a psu. On these graphs, looking up the most efficient psu's is a disappointing ta...

Most computers are in idle mode a large part of the time. Modern systems use 10-20 watt idle, but their psu's easily draw double that from the wall. Not testing this system for efficiency at lower powers is a missed opportunity...