As computers become more and more power hungry, they also require stronger power supply units to feed them. Typically, the more power a single unit has to provide, the less efficient it becomes. While it may be supplying the computer itself with 500 Watts of power, it'll actually be using significantly more. Most power supplies are around 70% efficient, leaving significant room for improvement and reduction in power waste. Lately, Antec has released a line of PSUs that meets the 80 PLUS requirements, a program that helps to reduce waste in the computing world.
Antec's new "EarthWatts" PSUs carry a minimum of 80% power efficiency, and are available in configurations in up to 500W. This makes them quite ideal for almost all desktop systems, and a good fit for people looking to create quiet, power efficient computers. The price range isn't that much different compared to other PSUs, with the 380W model being $65 and the 500W model ringing it at $100. Antec isn't the only company with 80 plus certification, which you can find out more about on their site.