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 Post subject: [power] Are my calculations correct?
PostPosted: Tue Aug 07, 2012 2:36 am 
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Hello

Out of curiosity, I wanted to know how much power my desktop computer used by leaving it running 24/7, and whether it was worth switching to a laptop that could really turn to suspend mode while the desktop still has its CPU and PSU fans running when I tell XP to go to suspend mode.

For a desktop with 400W PSU + two SATA drives + basic video chipset on the motherboard + basic LCD screen that I put into sleep mode when I'm not using the computer, does this sound about right?

300W * 24h * 365d = 2.628.000 watt/hour, or 2628 KwH
2628 * 0.10€ = 262,8€/year

http://michaelbluejay.com/electricity/computers.html

Provided this looks plausible, I assume a laptop with a single drive (+ a NAS that can wake up at night through WoL) uses a lot less power when in suspend mode?

Thank you.


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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Tue Aug 07, 2012 3:19 am 
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300W sounds way too much if there's no discrete graphics card in there. I'd expect something in or around the double-digits watts (ie. <~100W).

What CPU are you running?


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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Tue Aug 07, 2012 3:33 am 
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No regular PC will draw 300w of power all the time. Even multi-GPU overclocked abominations will struggle to hit 200w when not stressed (called idle).

Depending on the CPU you use, your PC (with integrated graphics) should idle between 50-100 watts and between 75-150 watts on load. How much time it spends on load depends on your usage. Web browsing & word processing can be considered idle. Watching videos, photoshopping, video editing can be considered medium load. Gaming would be high load. Video encoding, 3D rendering or Folding would be full load. You'd have to assess how much time of your PC's power-on-hours you spend doing these activities.


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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Tue Aug 07, 2012 3:46 am 
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Hi, my over-clocked i7 + GTX560 Ti gets up to 330w fully maxed out with Folding@Home on CPU + GPU. Only the most crazy over-spec PC will idle at 300w, a modern PC that throttles back the CPU and GPU at idle should be easily under 100w.

Also there is no reason why a desktop PC can't go to sleep like a laptop. PC have had the ability to go to "S3" sleep for quite a few years now. In proper S3 sleep all the drives and fans etc are powered down as are the CPU and GPU, in fact only the RAM is powered up and the power draw from the wall should be <10w and the PC should wake up from S3 sleep in litterally a few seconds.

Regards, Seb

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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Tue Aug 07, 2012 7:08 am 
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As others have pointed out, your estimates are very high. You can buy a stock desktop PC that will idle at 50W, you could buy a small form factor desktop that idles in the 20W range, you can buy a smaller form factor desktop that uses laptop parts and get the idle down to 15W or less, and then add whatever power your monitor uses. All can be set up to go into deep sleep/suspend modes and lower the power use into the 1 to 3W range.

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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Wed Aug 08, 2012 10:18 am 
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You can get ~10W idle with desktop gear now: viewtopic.php?f=28&t=64635


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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Wed Aug 08, 2012 11:37 am 
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nice

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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Wed Aug 08, 2012 12:27 pm 
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Thanks all for the input.

If desktop computers use so little power, I wonder why even the smallest PSUs can output 400W. But then, if the computer only uses 100W, does it matter if the PSU is a 400W model?

When I tell XPSP3 to go to suspend mode, the CPU fan and the PSU fan keep running while I expected them to shut down as well, or at least slow down significantly. Maybe it's XP's fault, maybe it's the mobo's fault, but for my next desktop, I want something that will be totally silent when it's suspended.

FWIW, the CPU is an AMD Athlon 64 X2 5200+ and the mobo is an ASUSTeK Computer INC. M2N68-AM Plus (AM2).


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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Wed Aug 08, 2012 2:03 pm 
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Depending on the age of your 5200+, the TDP is either 65W or 89W. Worst case, use the 89W figure for full load power. Add ~30W for the mobo, 16W for the two HDD, 10 watts for fans, keyboard, mouse, etc...call it 145W DC. If your PSU is an old piece of excrement, it might have 65% efficiency at load. So, 225W AC.

If you have the 65W CPU and a 80% PSU, then it's ~150W AC...and if the PSU is 90% efficienct, load power is ~135W AC.

Plus your LCD monitor.

-->But then, if the computer only uses 100W, does it matter if the PSU is a 400W model?<--
Here's the boundary conditions:
- You want a PSU that provides good efficiency when the PC idles. PSU efficiency is a curve vs load, not a flat line and it drops off like a cliff at lower loads. So, if your system idles at, say 50W, the 300W PSU will have better efficiency than the 500W one (of the same model series).
- You want a PSU with enough wattage to cover your system, plus some breathing room for temperature and lifetime derating.
- You want a PSU that meets your needs for quiet/silence at the PC's load.

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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Sun Aug 12, 2012 2:55 am 
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Thanks for the infos. Is there a web site where we can search for the different components and find how much power they use?

Also, are booksize computers dead-silent and powerful enough for office use, or should I really build my own?
www.newegg.com/Store/Category.aspx?Cate ... -Computers

The reason I ask is that those items are probably cheaper to buy as a ready-to-use computer than buying parts and buidling my own.


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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Sun Aug 12, 2012 7:42 am 
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The book-sized barebones with low-power CPUs are sometimes quiet or even silent.

I've never seen a very quiet book-sized barebone featuring mainstream CPUs.
They can be quiet enough for some people however. It depends on your hearing and noise floor.

If you know what you're doing, you can beat the price of the barebones (with my local prices anyway) and/or get better features and/or lower noise by buying case, CPU heatsink/fan and motherboard separately. It often makes sense to buy a case/PSU bundle though (many of the smallest cases include one anyway).


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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Sun Aug 12, 2012 3:19 pm 
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littlebigman wrote:
Also, are booksize computers dead-silent and powerful enough for office use, or should I really build my own?
http://www.newegg.com/Store/Category.as ... -Computers

Virtually NO booksize computers like the one you linked are "dead-silent". Most I would describe as moderately quiet or average -- in other words, not quiet at all by the standards of this site, especially when the computer will be atop the desk instead or beside or under it. Proximity matters for noise perception.

Almost all current computers are powerful enough for office use.

If I was in your situation, I'd look at assembling a system something like this.. with current CPU/motherboard:
http://www.silentpcreview.com/Silent_PC ... ving_Parts

Put the components in a good mATX case, and you'll be good to go.

Or maybe this:
http://www.silentpcreview.com/Single_Mo ... stone_TJ08

The key is a very large CPU heatsink you can run with a super slow fan or no fan, a silent PSU, a solid state drive, and integrated video rather than a discrete graphics card. With a modern Sandy/Ivy Bridge CPU and a high efficiency 80+ Gold PSU, the system will idle as low as 30W and top out no higher than ~70W. It can be quieter than any laptop.

I'm sure someone here can slap together a quick component list.

Cost? Maybe $500, depending on SSD size.

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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Sun Aug 12, 2012 8:28 pm 
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With a Windows license, it's closer to $560. :) Here's a build:

Case $100 seems like any decent case costs $100.
Mobo Gigabyte GA-H61MA-D3V uATX $55
CPU Pentium G620 2.6GHz $64
Cooler Scythe Big Shuriken 2 Rev B/etc… $50
RAM Samsung 2x2GB $24
SSD Samsung 830/Crucial M4 128GB $105
HDD ?
PSU Seasonic SSR-360GP 360W gold $60
OS Windows Home Premium 64-bit OEM $100
Total $558

I haven't paid attention to tiny cases. Don't have a recommendation. The gigabyte mobo has SATA 6GB and USB 3. The G620 is as low as I'd go for a CPU. Seems like all the decent coolers are in the $50 range. Big Shuriken for low skyline, Mugen 3 perhaps if have room...have to look at mobo clearance... I like the Samsung RAM. 128GB SSDs are in the $100 range now. I like these two. Don't know if you need a HDD. Hey, Seasonic has a $60 80+ Gold PSU now.

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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Mon Aug 13, 2012 11:33 am 
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CA_Steve wrote:
With a Windows license, it's closer to $560. :) Here's a build:

Case $100 seems like any decent case costs $100.
Mobo Gigabyte GA-H61MA-D3V uATX $55
CPU Pentium G620 2.6GHz $64
Cooler Scythe Big Shuriken 2 Rev B/etc… $50
RAM Samsung 2x2GB $24
SSD Samsung 830/Crucial M4 128GB $105
HDD ?
PSU Seasonic SSR-360GP 360W gold $60
OS Windows Home Premium 64-bit OEM $100
Total $558

I haven't paid attention to tiny cases. Don't have a recommendation. The gigabyte mobo has SATA 6GB and USB 3. The G620 is as low as I'd go for a CPU. Seems like all the decent coolers are in the $50 range. Big Shuriken for low skyline, Mugen 3 perhaps if have room...have to look at mobo clearance... I like the Samsung RAM. 128GB SSDs are in the $100 range now. I like these two. Don't know if you need a HDD. Hey, Seasonic has a $60 80+ Gold PSU now.

Like I said, someone will come up with a list quick -- thanks Steve, esp. the news about Seasonic's 360W gold.

I beg to differ re the case & CPU, tho -- a Fractal Core 1000 case is around $30, and good enough. Biggerr than "bookcasee" but fairly small, and way quieter. And any dualcore Celeron Sandy/Ivy Bridge like G540 (2.5GHz, 65W) or G530 (2 GHz but just 35W) will handle 98% of office tasks w/o issue -- there's little performance difference between them and low end Pentiums but they can be had for as low as ~$40.

I also think the low cost cooler champ Coolermaster 212 would probably be good enough, esp w/undervolted -- they can be had for as low as $30.

Take those savings into account and you're well under $500 even if you do choose to pay the microsoft tax. ;)

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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Mon Aug 13, 2012 12:27 pm 
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Lots of people like smaller cases and many do find book-sized cases effectively inaudible as long as a relatively weak CPU like the G620 is used.
A popular choice would be Antec 110 (includes fanless power supply in the price) + Kozuti for instance. That's in the barebone price range, and less noisy.

The G530 is rated 65W, not 35W. Not that the rating matters. Please don't perpetuate people's confusion by quoting it as if it mattered.

It is not at all clear that the Microsoft tax for end-users is only $100 by the way.


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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Mon Aug 13, 2012 1:22 pm 
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HFat wrote:
Lots of people like smaller cases and many do find book-sized cases effectively inaudible as long as a relatively weak CPU like the G620 is used.
A popular choice would be Antec 110 (includes fanless power supply in the price) + Kozuti for instance. That's in the barebone price range, and less noisy.

The G530 is rated 65W, not 35W. Not that the rating matters. Please don't perpetuate people's confusion by quoting it as if it mattered.

The OP asked about "dead-silent" -- a Kozuti is not that, not when it will be atop the desktop. But maybe if mounted on the back of the monitor.

I must have misread the power rating, the G530 is also 65W, and there's no real price difference between that and the G540, so the latter's a better choice. It is true the TDP rating doesn't matter much, as even at maximum load, there's much less than 30W difference between 65W and 35W Intels these days.

But, HFat, don't lecture me in that dismissive tone designed only to irritate.

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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Mon Aug 13, 2012 7:00 pm 
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MikeC wrote:
Take those savings into account and you're well under $500 even if you do choose to pay the microsoft tax. ;)

Dude, Redmond is just a short hop from Vancouver. Keep this up and they might invade. You'd never hear the MS assault troops use the ram on the door when you are in the chamber, either :D

Some clarification for HFat. I often see the OEM license for $90 at Newegg, Fry's, etc.

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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Thu Sep 13, 2012 2:58 am 
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Thanks everyone for the infos on building a quiet home PC.

So it looks like NewEggs overestimates power needs by a long margin: With...
  • CPU = AMD Athlon 64 65nm
  • Mobo = Regular - Desktop
  • Video = integrated
  • Memory = 2GB
  • Op drive = DVD-RW
  • Hard drive = 7200RPM 3.5 x 2

"Our recommended PSU Wattage: 243 W". Apparently, that's much higher than such a desktop computer would actually use, even at boot-time.


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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Thu Sep 13, 2012 3:27 am 
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littlebigman wrote:
I put into sleep mode when I'm not using the computer

Why not save yourself some money and switch it off completely? There still perpetuates this myth in some circles that computers should be left on all of the time because it extends their life which hasn't held for decades. Even with everything in a soft-off mode there will still be ~10W being used which multiplied by all of the computers in the world adds up to a lot of wastage.

I have to side against the very small book sized computer cases. Not just from a silence perspective but also from a future proofing perspective. Some of them use obscure non-standard parts like PSU and CPU cooler which may make things difficult to maintain/upgrade down the line to the same extent you would find with a laptop. There is more interest in them from the big makers in the same where there is for laptops because there is more money to be made on them and due to their lack of future-proofing repeat business is easier to come by.

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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Thu Sep 13, 2012 7:44 am 
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edh wrote:
Even with everything in a soft-off mode there will still be ~10W being used which multiplied by all of the computers in the world adds up to a lot of wastage.


Depending on the age of your PSU and other hardware, the ~10W might be a myth. My current setup "sleeps" at ~1W. On the other hand, my old Sonata based PC was using 5W when off. :D

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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Thu Sep 13, 2012 8:58 am 
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CA_Steve wrote:
Depending on the age of your PSU and other hardware, the ~10W might be a myth. My current setup "sleeps" at ~1W. On the other hand, my old Sonata based PC was using 5W when off. :D


The OP was looking at the sleep power consumption including the monitor, hence it's going to be closer to 10W than 1W. You are right though, it does vary depending upon PSU, motherboard and other components, I've seen anywhere from 1W to 7W excluding monitor.

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 Post subject: Re: [power] Are my calculations correct?
PostPosted: Thu Sep 13, 2012 10:35 am 
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I was including my two monitors :)

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