A Wikipediabol (http://en.wikipedia.org/wiki/Computer_power_supply):
" * Quality computer power supplies usually have about 80% energy efficiency, the higher energy efficiency the better. A power supply with a higher energy efficiency will decrease the amount of energy lost to heat. As of 2007, there are power supplies with 88% energy efficiency.
* The energy efficiency is lower at low loads. The energy efficiency generally peaks at about 50-75% load. The curve varies from model to model.
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