Guidelines, Rules, And Regulations
One of the most important indicators of a PSU’s efficiency is whether it complies with the Energy Star 5.0 guidelines and the 80 PLUS standard. The latter applies primarily to computer power supplies and is recognized worldwide. Additionally, if you’re located in a European country, CE conformity and compliance with ErP guidelines are also important.
80 PLUS PSUs Are More Efficient
The specifications, norms, and guidelines we just mentioned all call for high efficiency, as well as improved power quality. Power supplies that conform to these demanding and very strictly-interpreted rules by passing a defined set of tests may then be marked with the 80 PLUS badge appropriate to its efficiency level. While the load/stress tests may not correspond to those defined by the ATX specification, that’s acceptable in this case. Here’s some good news for our European readers: since the tests are conducted using the lower US voltages, these power supplies achieve even higher efficiency levels in the European 220 V grid.

80 PLUS: Platinum, Gold, Silver, Bronze
The original concept of the 80 PLUS certification has been revised, adding new, more strictly-defined efficiency levels. The bronze, silver, gold, and platinum certifications each come with their own requirements. Thus, a PSU that is certified “80 PLUS Gold” or “80 PLUS Platinum” is more efficient than a normal unit. The downside is that the more complex circuitry needed to hit those levels generally results in a higher price tag, too.
Below you’ll find a table that shows what efficiency levels a PSU has to achieve at a given load to make the grade for a specific certification level.
| Efficiency at 20% Load | Efficiency at 50% Load | Efficiency at 100% Load | |
|---|---|---|---|
| 80 PLUS | 80% | 80% | 80% |
| 80 PLUS Bronze | 82% | 85% | 82% |
| 80 PLUS Silver | 85% | 88% | 85% |
| 80 PLUS Gold | 87% | 90% | 87% |
| 80 PLUS Platinum | 90% | 92% | 89% |
When Off Isn't Really Off: A Few Words On Standby Power Consumption
When you shut down your computer, the PSU doesn’t really switch off completely. This is necessary for features such as Wake-on-LAN to work. The point is that the power supply keeps drawing some power, even when the computer is off. Newer PSUs, especially ones sold in Europe and certified to be ErP/EuP-compliant, draw less than 1 W in this standby mode. If you’re serious about conserving power, go for a newer model with ErP support.
Which Power Rails Are Important?
That brings us to one of the most crucial points of modern power supplies: namely, the power they are able to supply at various voltages. Nowadays, PCs draw the majority of their power from the +12 V rail. By comparison, the other two voltages, 3.3 and 5 V, play a far less important role. That’s why you can use the following as a rule of thumb: if a PSU’s 12 V rail can supply all of the required power with room to spare, then the lower voltages are sufficient as well.
However, the opposite is not necessarily the case. Let’s compare the spec stickers of two PSU models:

The difference is quite obvious. Although the second model is billed as a 550 W unit, its +12 V rails only add up to 380 W, and even that only holds true if the other rails aren’t being stressed simultaneously! Nobody needs 315 W on the 3.3 and 5 V rails. In practice, this power supply would probably reach its limit at a load of 350 W on the 12 V rail.
Ironically, even a good 425 W PSU could push more power than this model at 12 V. Don’t fall for this sort of trickery.
Initial Cost Vs. Energy Savings
Quality products cost more initially, but that doesn’t necessarily always translate into lower cost in the long run. That’s why we’ll take a look at a few specific components and their prices in a moment to determine the type of PSU makes the most sense in a given environment, and what kind of savings you can achieve, if any. Some of the results may surprise you!
It’s not enough to focus solely on the financial aspect, though, because we also have to consider durability, reliability, and safety. We go into more detail on these points on the next page.
- Brought To You By Granny’s Radio
- How A Switching Power Supply Works
- Efficiency, Efficiency, Efficiency!
- Of Power Factors, Apparent Power, And Effective Power
- How To Spot An Efficient PSU?
- Don't Get Burned: Safety Before Stinginess
- How To Determine Your Power Requirements
- The Power Window Is Important
- Example 1: The Office PC
- Example 2: Mid-Range Gaming PC
- Example 3: The Enthusiast’s System
- If You Don't Like Our Advice, Buy A Fire Extinguisher


unfortunately that is not always the case, you could buy a resonably expensive Thermaltake TR2 RX series and end up with a piece of crap.
i want
Would like to see more articles written like this.
Well written, and well done !!!
i want
No one really listens to this.
unfortunately that is not always the case, you could buy a resonably expensive Thermaltake TR2 RX series and end up with a piece of crap.
Now I got a CM PSU and no problems since!
Helps keep the Phenom under control.
most good psus are able to out live a pc build under 24/7 use, some able to last 10 years.
where i live power costs 11 cents per kwatt. it should be 9 like my state average, but whatever, i wont go into that further here.
now with 11 watts difference, over the coarse of 1 year under 24/7 use, that comes out to about 10$ and out national average is also 11.2 cents, so rounding down to 11 is appropriate.
now here are some numbers, based on estamates.
11 watts - 10$ a year
22 watts - 20$ a year
33 watts - 30$ a year
and lets go with a pc thats built right lasts 4 years, and is used for 5 (waiting on parts to be released and such)
base/4year/5year
10/40/50
20/80/100
30/120/150
basically you have to look at the long run, and anticipate a mid cycle upgrade, such as new gpu, with 50-100 more watts headroom.
lets also assume that you turn the pc off at night, some people do, but leave it on all other times. even at half the cost, on the gameing, and mid range, its more cost effective to buy the better psu, the highend though, used a 750 watt Corsair, there should be a 550 or 600~ watt one that would be cheaper and better fit in line with the other psus tested.
more to the point. we needs a toms chart for psus, right now we have a efficiantcy chart, but what we need is a build chart.
one that takes the psus, and puts them in a standard pc enviorment, like the ones here, and measures the watts used.
than gives us a baseline like this one is 100% than how much more the ones above use in %, than in numbers next to it, and than figuring the annual power cost for the extra watts they use, and find out which ones really the best for your builds, assuming a 4 year build cycle with a 5 year use, like i did above.
i honestly think that could result in an interesting benchmark.
Yes but in most cases if you buy something cheap the vast majority of the time it's going to be cheaply made so therefor it will break a lot faster then something you buy at a preimuim that's has quality. Your odds of getting a lemon Bently is a lot lower then buying a Dodge that's a lemon. of coure you pay a hell of a lot more for the Bently then your typical dodge but that's because you are paying for the high preimum of quality and craftsmenship that goes into it vs something that is made mostly by a machine.
Would like to see more articles written like this.
Well written, and well done !!!
Beware of retailers that don't pass on full specs. Always check the manufacturer website for specs. Some retailers seem to forget to add complete descriptions for PSUs (and products in general too) which they have to order, but seem to add more info to the ones they have on stock. Probably to make them look better so they get rid of it faster. Living in Romania I already have "blacklisted" quite a few retailers from which I'll never EVER buy, based on this solely alone. It was actually very subtle, and it wasn't that they simply "forgot" either. As soon as I noticed this discrepancy I started to question their entire business model. Didn't even bother to tell them (didn't want to) because I'd rather have some other smart person catch on to their scheme instead of guiltying them into correcting it.
CM PSUs aren't that amazing either
http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/index.htm
Look for the symbol on the PSU label that looks like a backward "R" next to a "U". Under that symbol, you will find the letter "E" followed by a 6-digit number. Put that in the UL Online Certification Directory on the line that says "UL File Number" and it will tell you who that file number belongs to. For example, you would find that some Silverstone PSU's are made by Silverstone, some are made by "Enhance Electronics Co. LTD." and some are made by FSP.
Fast forward another year sitting in a 100yr old dorm room with a power grid that was not meant to run the amount of draw that we were all pulling, and we were all loosing parts left and right. This was long before active power correction was normal, or even affordable. But I lost my video editing rig right in the middle of finals week, and it was entirely due to the power available (though not the power supply that lasted me several more years without problems when I moved out of the dorms).
On my last build I bought a very nice 500W power supply that has all of the modern niceties of voltage regulation and power protection (as well as the power connectors that the old supply did not have), but now that I am looking at doing a new build next year I am not sure if it will be big enough. I think it will be fine at first, but I am going to do SLI down the line, and according to the math here I am going to need a peak of ~900W available, meaning I need a ~1000+W PSU... and that is going to hurt the wallet