text_combined: aaron kulkis cmiqlkx91hotpopcom per jessen wrote aaron kulkis wrote power supplies generally rated much power consume much supply relatively direct connection two matter yes 80 efficient 400w power supply rated supply 400w power consuming 500w rated consume 400w power supplying 320 w yes matter 400w devices needs 500w power supply youre demonstrating really dont know enough subject give qualified comments perhaps took electrical engineering courses specifically course electric power impedance matching big issue well qfactors things huge impacts efficiency aaron appreciate comments except youre bsing sake right list discourse switchmode powersupply design im correcting crazytalk 100 false power supply rated output mid 1908s worked electronics short switchmode supply could achieve 80 efficiency without major design effort im assuming still possible even substandard components designers market wattsdollar primary means comparison consumers uninformed simply lowestpriced powersupply meets whatever believe system load translates cheap components 20 resistors instead 5 1 similarly sloppytolerance components parts construction power supply get 80 efficiency across board trivial thing disagree even relatively poor inexperienced design achieve aiming 90 higher less trivial many power supplies dont meet 80 acrosstheboard standard 80plusorg youre really qualified advise others subject please tell us exactly qualified judge im electrical computer systems engineer tue 05 aug 2008 205245 0500 opensuse power supply psu efficiency