Category Archives: power supplies

Energy Efficient Power Supplies: Part 2

A Seasonic 80+ Gold Modular Power Supply is the Perfect PSU for my Dual Opteron 4184 12-Core Server

A Seasonic 80+ Gold Modular Power Supply is the Perfect PSU for my Dual Opteron 4184 12-Core Server

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.

80+ Efficiency Table

80+ Efficiency Table

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.)

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Efficient Power Supplies: Part 1

Good morning!  This is an intro article…feel free to skip if you already know what efficiency means for power supplies.  Part 2 goes into detail of the 80 Plus standard and is likely a more enthralling read for you spec heads!

Let’s talk about the most important piece of hardware that a desktop computer can have…the power supply!  This little guy is responsible for electrifying all the goodies inside your computer.  Furthermore, a good power supply protects your computer from dirty power (voltage spikes, EMI ripple, power fluctuations, etc).  If you have ever read an article on custom desktop building, you probably know how crucial a good power supply is, as well as the consequences of using a cheap PSU.  Suffice it to say that, for the sake of your computer’s health, this is one area where you don’t want to skimp on cost.

There is one trait of quality power supplies that is often overlooked, and that is energy efficiency.  In a perfect world, a PSU would convert every watt of 120 V AC input power into usable DC power.  In reality a portion of the power is lost as heat.  The more efficient a power supply, the less energy it wastes as heat.  In other words, your computer simply draws fewer watts from the wall.

Having an efficient power supply is crucial for F@H contributors and non-folders alike, because it will make your computer less power hungry no matter what it is doing.  From gaming and graphics design to office work and Folding@Home, an efficient PSU will put a smile on your P3’s cute little face.  (If you don’t get the reference, please also read the previous post about Watt meters)

Before I go on, I should note that the target audience of this article is those who have built or are building their own custom desktop.  People with laptops or with name-brand consumer desktops are sometimes out of luck because the power supplies are often proprietary and can’t be upgraded.  However, it doesn’t hurt to find out from the manufacturer of your computer what the efficiency of your power supply is.  Some brands, such as Dell, HP, and Apple (among others) do have energy efficient power supplies of varying levels in their machines.

Cheap No-Name Brand Power Supply Unit that Came with a Case Bundle

Cheap No-Name Brand Power Supply Unit

If your power supply looks as lame as the one in the above pic, then it probably has an efficiency rating of 60 to 70 percent.  This means that if your computer parts need roughly 200 watts of power to run, your PSU might draw 250 watts or more from the wall in order to supply the 200 watts of DC power.  That extra 50+ watts is wasted as heat.

PC Power & Cooling SILENCER PSU

PC Power & Cooling SILENCER PSU

Seasonic SS-380GB PSU Installed

But, if your power supply looks like the one in Pic # 2 or #3, it might be closer to 80 or 90 percent efficient.  For that same 200 watt load, it is only drawing perhaps 220 watts from the wall.  The thirty watt difference might not seem like much, but for a Folding rig running 24/7 the wasted wattage of the el-cheapo unit adds up.  Let’s assume we are running a machine with the craptastic PSU.  To calculate the total extra energy wasted relative to the better PSU (remember, watts is a power quantity, which means energy/time), we need to multiply the wasted wattage by the amount of time the computer was in service to get an energy quantity in watt-hours.  So, 30 watts * 24 hours/day * 365 days/year = 262800 watt-hours.  Converting to kilowatt hours (dividing by 1000) gives 262.8 kWh.  Assuming an average electricity cost of ten cents per kWh, we get an annual cost of 262.8 * 0.10 $/kWh = $26.28.  Assuming the folding computer is running with that same power supply for 5 years (mine has been going for longer), that is over $125 wasted dollars, not to mention a slap in the face for poor planet Earth!  A good energy efficient PSU could have been bought for $40 in the first place to negate this wasted energy cost and lessen the environmental impact.

So how can you spot an efficient power supply unit?  Well, for that you can go by the independent test & certification program known as 80+.  I will cover this in detail in the next article, so that people who want to jump right into the specs and skip this intro can do so.