The last post gave an overview of why efficiency matters for power supplies. This post is focused on how to pull this off in practice. The 80+ (80 Plus) certification is an optional certification that power supply makers can get on their retail PSUs by submitting samples for testing at an independent lab. There are various levels of efficiency rankings within the standard, but any unit that achieves the basic 80+ rating can be considered efficient compared to the average 60-70% efficient PSUs of old.
For around the clock computer operation, you should get the most efficient unit possible, although the 80+ Platinum and Titanium units can be cost prohibitive. My recommendation is to stick with an 80+ Gold unit, because they are significantly more efficient than most power supplies and can be obtained without first having to sell a kidney on the black market. Note that the greatest efficiency can theoretically be achieved by selecting a power supply that has a rated maximum wattage of twice what your computer requires to run F@H full-blast. For example, if your shiny new F@H rig requires 300 watts of power to run, getting an 80+ Gold PSU rated at 600 watts should guarantee you an excellent efficiency rating of 90%. This is because power supplies tend to be most efficient at 50% of their rated maximum load.
For many power supplies you can find an efficiency curve that graphs out the unit’s efficiency vs. load, but to save yourself valuable time you might as well just buy a reputable power supply from a good manufacturer that has the 80+ Gold certification. As with any computer part, read the user reviews before purchase to avoid a serious frowney face later. JonnyGuru.com has some excellent power supply reviews, and they test their review samples in a much more grueling temperature environment than the 80+ standard requires. When buying from Newegg, just filter your PSU search by efficiency rating and then by user reviews to immediately find some good candidates. My personal favorite is the Seasonic X-series of Gold-rated PSUs, although Antec, PC Power & Cooling, Thermaltake, Cooler Master, Corsair, and many others also make good units. I have been using the Seasonic X-650 Gold, which is a great power supply for a bunch of reasons other than efficiency (modular cables, multiple PCI Express power connections, a smart fan, the latest ATX standard, great build quality, and so on until I’m blue in the face). The Seasonic has reduced my desktop’s power consumption by over 32 watts at idle and 49 watts at load, compared to the Ultra X2 connect 500 watt PSU I had before. I pitched the old one into the computer recycling bin at the local transfer station to make sure it stays out of service. It made a nice sounding kerthunk, by the way. (Random environmental tip: Most city dumps take recycle computer electronics for free, so take your old wasteful power supply as well as any of those nasty compact fluorescent mercury-ridden light bulbs to the dump for recycling instead of throwing them in the trash.)