Corsair has a family of PSUs (power supply units) for PCs that are on the way to meeting the stringent new EnergyStar 5.0 requirements worked out between the EPA and the hardware industry. EnergyStar 5.0 will require 85% efficiency at idle and load. The 80 PLUS certification means that 80% or greater efficiency is achieved at 20, 50 and 100% loads. I have one of the HX620W PSUs that meet the 80 PLUS standard in the pc I'm typing on now. I bought it specifically after searching the web, and finding articles at places like overclock.net, for efficiency information. There is no point in turning electricity into heat if you don't have to (especially in a St. Louis summer and a world where energy is costly in so many ways).