Category Archives: power supplies

Power Supply Efficiency: Let’s Save Some Money

A while ago, I wrote a pair of articles on why it’s important to consider the energy efficiency of your computer’s power supply. Those articles showed how maximizing the efficiency of your Power Supply Unit (PSU) can actually save you money, since less electricity is wasted as heat with efficient power supplies.

Efficient Power Supplies: Part 1

Energy Efficient Power Supplies: Part 2

In this article, I’m putting this into practice, because the PSU in my Ubuntu folding box (Codenamed “Voyager”) is on the fritz.

This PSU is a basic Seasonic S12 III, which is a surprisingly bad power supply for such a good company as Seasonic. For one, it uses a group regulated design, which is inherently less efficient than the more modern DC-DC units. Also, the S12 is prone to coil whine (mine makes tons of noise even when the power supply is off). Finally, in my case, the computer puts a bunch of feedback onto the electrical circuits in my house, causing my LED lights to flicker when I’m running Folding@Home. That’s no good at all! Shame on you, Seasonic, shame!

Don’t believe me on how bad this PSU is? Read reviews here:

Now, I love Seasonic in general. They are one of the leading PSU manufactures, and I use their high-end units in all of my machines. So, to replace the S12iii, I picked up one of their midrange PSU’s in the Focus line…specifically, the Focus Gold 450. I got a sweet deal on eBay (got a used one for about $40, MSRP new on the SSR-450FM is $80).

SSR-450M Ebay Purchase Price

Here they are side by side. One immediate advantage of the new Focus PSU is that it is semi-modular, which will help me with some cable clutter.

Seasonic PSU Comparison: Focus Gold 450W (left) vs S12iii 500W (right)

Seasonic PSU Comparison: Focus Gold 450W (left) vs S12iii 500W (right)

Inspecting the specification labels also shows a few differences…namely the Focus is a bit less powerful (three less amps on the +12v rail), which isn’t a big deal for Voyager, since it is only running a single GeForce 1070 Ti card (180 Watt TDP) and an AMD A10-7700K (95 Watt TDP). Another point worth noting is the efficiency…whereas the S12iii is certified to the 80+ Bronze standard, the new Focus unit is certified as 80+ Gold.





Now this is where things get interesting. Voyager has a theoretical power draw of about 300 Watts max (180 Watts for the video card, 95 for the CPU, and about 25 Watts for the motherboard, ram, and drives combined). This is right around the 60% capacity rating of these power supplies. Here is the efficiency scorecard for the various 80+ certifications:

80+ Table

80+ Efficiency Table

As you can see, there is about a 5% improvement in efficiency going from 80+ bronze to 80+ gold. For a 300 watt machine, that would equate to 15 watts of difference between the Focus and the S12iii PSU’s. By upgrading to the Focus, I should more effectively turn the 120V AC power from my wall into 12V DC to run my computer, resulting in less total power draw from the wall (and less waste heat into my room).

I tested it out, using Stanford’s Folding@Home distributed computing project of course! Might as well cure some cancer, you know!

The Test

To do this test, I first let Voyager pull down a set of work units from Stanford’s server (GPU + CPU folding slots enabled). When the computer was in the middle of number crunching, I took a look at the instantaneous power consumption as measured by my watt meter:


80+ Bronze PSU: 259.1 Watts @ Full Load

260 Watts is about the max I ever see Voyager draw in practice, since Folding@Home never fully loads the hardware (typically it can hit the GFX card for about 90% capacity). So, this result made perfect sense. Next, I shut the machine down with the work units half-finished and swapped out the 80+ Bronze S12iii for the 80+ Gold Focus unit. I turned the machine back on and let it get right back to doing science.

Here is the updated power consumption number with the more efficient power supply.


80+ Gold PSU Power Consumption @ 100% Load

As you can see, the 80+ Gold Rated power supply shaved 11.8 watts off the top. This is about 4.5% of the old PSU unit’s previous draw, and it is about 4.8% of the new PSU unit’s power draw. So, it is very close to the advertised 5% efficiency improvement one would expect per the 80+ specifications. Conclusion: I’m saving electricity and the planet! Yay! 

As a side note, all the weird coil whine and light flickering issues I was having with the S12iii went away when I switched to Seasonic’s better Focus PSU.

But, Was It Worth It?

Now, as an environmentalist, I would say that this type of power savings is of course worth it, because it’s that much less energy wasted and that much less pollution. But, we are really talking about just a few watts (albeit on a machine that is trying to cure cancer 24/7 for years on end).

To get a better understanding of the financial implications of my $40 upgrade, I did a quick calc in Excel, using Connecticut’s average price of electricity as provided by Eversource ($0.18 per KWH).

Voyager PSU Efficiency Upgrade Calc

Voyager PSU Efficiency Upgrade Calc

Performing this calculation is fairly straightforward. Basically, it’s just taking the difference in wattage between the two power supply units and turning that into energy by multiplying it by one year’s worth of run time (Energy = Power * Time). Then, I multiply that out by the cost of energy to get a yearly cost savings of about $20 bucks. That’s not bad! Basically, I could pay for my PSU upgrade in two years if I run the machine constantly.

Things get better if I sell the old PSU. Getting $20 for a Seasonic anything should be easly (ignoring the moral dilemma of sticking someone with a shitty power supply that whines and makes their lights flicker). Then, I’d recoup my investment in a year, all while saving the planet!

So, from my perspective as someone who runs the computer 24/7, this power supply efficiency upgrade makes a lot of sense. It might not make as much sense for people whose computers are off for most of the day, or for computers that just sit around idle, because then it would take a lot longer to recover the costs.

P.S. Now when I pop the side panel off Voyager, I am reminded to focus…

Voyager New PSU

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. 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.)

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.