Power Factor Correction
Power Factor Correction (PFC) comes in two flavors: Active and passive. Less expensive PSUs skip this altogether, simply not listing it or listing it as "no," in the case of Newegg. Some power that is being pulled from your outlet never makes it to the computer due to various reasons - heat, inefficiency, and the general rule that there is never 100% efficient energy conversion or transfer. PFC increases the amount of power that makes it to your rig in a few different ways, making your PSU more efficient.
Using relative numbers, a complete lack of Power Factor Correction will result in somewhere around a 0.6 in PF (power factor), while passive PFC spits out somewhere around .725 PF, and active PFC provides the best efficiency and is nearly ideal, offering PFs of as much as .99. Note that most PSUs priced at $100 or over will use Active PFC. Power Factor is rated from -1 to 1, with 1 being a theoretical perfectly efficient solution.
See Also
- Rails (PSU)
- Overvoltage Protection
- Voltage Ripple