Power Supply Efficiency
 

I'm setting up a new computer... And I took a peek at my power supply....

100-127V - 8A

So that's fully loaded power....

So 110V *8A = 880Watts

The supply is rated to deliver 300W max...

That's to say, fully loaded my power supply has an efficiency of 34% :eek: Yes, fully loaded is one of the least efficient zones - but still, 34%?

I found a similar power supply (same model and power reqs/specs with a couple different connectors) that claims 70% minimum efficiency
ATX12V-G300BT (Bestec ATX-300-12EB3 Power Supply)

Any other explanation? What's your box say?

Look for articles about multiple Power Supplies compared at Tom's Hardware: Hardware News, Tests and Reviews

No time now - got to leave in a minute.
Will look up the specific article and write more on this tomorrow.

Hi,

A much better source of info about power supplies is one of my other haunts: Silent PC Review.

silentpcreview.com | Everything about Silent / Quiet Computers

Typical older units were in the 65-75% efficiency range (though some are lower), and now 80-85% are fairly common. A few units are approaching 90% now; and it also depends a lot on your actual consumption. Most computers are 100-200 watts of DC consumption, so add ~25-30% to that for the AC use.

Wasn't aware of that site. Good find, looks like their tests are as through as Tom's Hardware.

Here a link that takes you straight to the Power Supply Articles & Reviews at Tom's Hardware.

And here is a link that takes you straight to the Power Supply Articles & Reviews at Silent PC Review.

Silent PC's article about Power Supply Fundamentals looks particularly good.

The specific article at Tom's Hardware that I had in mind is
Inadequate and Deceptive Product Labeling: Comparison of 21 Power Supplies
Lawyers, politicians, statisticians and Power Supply Manufacturers - they all tend to bend the truth and a significant number of each one tell out and out lies. Take manufacturer's specification numbers with a great, big block of salt. Shop for specific units that have performed well in tests conducted at one of the above sites. Or shop for brands that consistently perform well in multiple tests conducted at one of the above sites.

Take a look at The 80 PLUS Program | Home for efficiency info on different maker's power supplies. I've been looking into this a lot recently. My power supply is probably 8 years old or so, it claims 70% efficiency at full load. I look forward to finding a new 85+% for whenever I do a new build.

Its pretty horrible when you look at the numbers. 70% efficiency and my computer at idle consumes 150W. That means I'm wasting 45 watts as a best case scenario!

Supposedly it's ~80% efficient at full load. Not bad for a $5 PS. :turtle:

The 8A is the fuse rating. It has nothing to do with actual load. Also, you'll need a True-RMS meter to accurately measure the current as it is very nonlinear.

Have you verified that number by a Kill-A-Watt or other meter? I HIGHLY doubt you'll be drawing 150w at idle, unless your monitor is factored in. With my Mac Mini, (smaller than your computer I imagine, but keep reading), 2 external hard drives, external DVD-writer on idle, USB hub with a cellphone charging off it, and a broadband modem, all while running file-sharing to the tune of 10-15mbps, (A lot of disk access), was only drawing about 65 watts average, at the wall, through a UPS. I only get up to about 150w with my monitor running.

Trebuchet: The 8A is maximum burst current draw. As in when all the motors in all the hard drives, dvd drives, and the processor are all drawing maximum load, while the PS capacitors are charging up, which is what happens in a start-up condition, when you have enough equipment tacked on to run the PS at full load afterwards.

Hi,

Mac Mini's and the new iMac's are exceptionally efficient and use very little power. 150watts is a bit higher than typical, but with a gaming video card, it is not hard to get the idle in that range.

Check out Silent PC Review for all sorts of good info on power supplies and efficiencies.

Yep, thats what the ol kill-a-watt tells me.

I just reformatted this weekend and ended up ripping out my sound card and extra network card. I'm now using onboard sound and lan. This dropped me down to 141W at idle.

Specs are:

Athlon xp 2500 barton core
Radeon X800 GTO
Seagate Cheetah ST336607LW 37gb scsi hd
Western Digital Caviar SE16 WD2500KS 250gb sata hd
Enermax EG365P-VE power supply


I'd be interested in knowing how much juice the scsi card and HD eat up.

hey. coincidentally, i dove back into the psu realm to get a new one.I ended up eith an earthwatts 380w. The twin hard drives have no more wah wah stray noise, it is nice.
I learned that "active pfc" is real, and I am enjoying my pc.PSU is a sensitive subject, I got electrocuted by a popular brand computer to the point of knocked out and exploding/chipping teeth for years afterwards. (claimed not be possible).
back to the future:
I do large functions on home made scripts (if to ponder 3400mhz at 100%, 167F degrees and ram floating full at 3gb for 24 hours or so) and the pc stays normal. Still screaming when it comes down, but the fan in psu winds up (like it knows it now).Active pfc is attributed to this, I have never had a psu that knew to wind up after the work is done to take away excess invisible..
passive pfc is done in my pc world. If to go for apfc psu, do get a late revsion, there is a year of sheisters in that too...(like all electronics) late 2007 and later is a good bet.
I could advice to look for the 2 (or more) 12v rails to be exactly the same output...that is all I learned and it worked.
speaking of silent pc review it is a favorite place, and I did write up about active pfc in a thread there with a simple analogy about how the volts go into non-efficient (written by the gov't, and i cut and pasted quotes)

browse around there is some smarter than I there to really answer questions.

Easiest way to build a green PC - Low power monitor, and conservative on the specs. Your daily use PC doesn't need to be a gaming machine with 500GB of HDD space. IF it does, you need to delete some of your pr0n.

OS tuneups are necessary, so get ready to work with software if you're not familiar already. Yes, Windows DOES become completely stupid after about 3 months of regular use. It happens, get over it and learn to fix it.

Keep programs that you use frequently loaded in memory on startup, lose everything else. This will allow you more room in memory before your computer needs to start using Pagefile (Virtual memory) to save things. virtual memory is a cell on your HDD that means your computer will wildly spin up your HDD randomly for a single data bit of memory that it takes ~400ms to find.

Don't use an 800w PSU if you don't need it. Overdoing it here can actually cost you a bit, as the capacitors and resistors and other components are more plentiful in a larger capacity PSU. They turn electricity into heat, moreso, the more of them there are.

These are just a few tips to help.

I actually use a 90W PSU in my old system, and I run 2 80GB IDE HDD's with a 700mHZ Athlon (card-style CPU, socket A) and 768mB ram. It runs XP, with a few tweaks to make it do it's job better, and more efficiently. It's actually faster than my old Vista retail PC at most daily functions.

Of course, you can save power by upgrading your internet connection too... the faster you browse, the less time you need to spend in front of your computer.

I just picked out my components (not ordered quite yet) for my new power efficient office/gaming system. It incorperates Nvidia's hybrid SLI technology to allow very low 2d operating power consumption while still having great 3d gaming performance. Basically, when in 2d mode it uses the onboard video GPU and powers down the video card. When you need to do 3d, it powers on your PCI-e video card (that would otherwise be guzzling down 40-60W all the time) and you get it's benefits. Great idea. This setup will allow my machine to idle well under 100W in 2d mode, yet still allow me to play anything I want game wise. I also went with an 85% efficient PSU and power efficient 45W AMD processor to keep power consumption down.

That's sounds like a great combo of power and efficiency there! Hope it works out for you.

I never thought of a 45W processor as being particularly efficient, especially when backing off the processing power a small amount yields disproportionately large dividends on the electrical side... but that may just be me. :p

Also on this subject... A PSU is a fairly simple device compared to the computer it runs, and almost all pre-built are built using bottom-of-the-barrel components... Has anyone attempted to build a PSU from raw components before?

I build guitar amps from scratch...

I don't think HD space has much to do with it, so much as the NUMBER of drives. I run 3, 1 internal 2 external, and they don't consume a lot of power really. Maybe 20W combined under load? Then again they aren't super-fast drives. I think they're 5400 and 7200 RPM drives. I've got about 830gb of disk space now, and I would reduce my energy consumption right now by replacing my 250 and 500 external drives with a single-disk 1tb unit.

And I figured out a way around Windows breakdowns... Ditch the Windows. All manners of Linux out there, that are actually getting quite user friendly now, and people still use Windows? Bah. :p

I agree. The 45W Athlon X2 5050e is what I bought. Its the lowest wattage chip for its speed currently avaliable AFAIK. I'll be combining AMD's cool'n quiet technology with crystalcpuid to lower power consumption even more.

When building my latest rig, I went for low power use. I had considered replacing the now 5 year old 300W Enermax supply with something more efficient, but I'm now glad that I did not. The cost benefit to going with an 80-Plus certified unit simply would not have been there with the dual core Atom based board I am using now. At full steam including the LCD monitor, it doesn't even break 90W of consumption on the Kill-a-watt, whereas the old AthlonXP that it replaced idled at about 125W and peaked around 200.

I know that my monitor draws about 15W on it's own, so 75W of consumption from a system that normally draws at least 65W out of the most efficient configuration is not bad since it's only on when I actually use it. So at best, a super-efficient PSU might save me 5W.

I would certainly demand over 80% efficiency out of any future supply that I buy, but older lower power supplies really aren't bad enough to warrant the upgrade when you start counting the pennies to do it.

Here's a tip for Linux users (and anyone willing try Linux):
Install a new version with kernel at least 2.6.22 and install PowerTOP. Since 2.6.21 the kernels are tickless, while PowerTOP is a tool for seeing which processes are causing the CPU to wake-up out of more efficient states. It also gives advice about what to change and how. PowerTOP was supposed to be for extending battery life in laptops, but you can use it in desktops also. Plus, both Linux and PowerTOP are free :)
I've been on Linux for almost 10 years now (Fedora 9 on the destop, F6 on the laptop to be upgraded soon). I have a small partition with WinXP programs which weren't writen for Linux, though I could just use the Wine emulator.