# What can a 350w PSU possibly run?



## Johnny1982 (Oct 15, 2010)

Hi guys, a little while ago I inquired about a basic PC that could support FullHD. This was for a friend of my dad and now I found out that he has already organised himself a PC. But I heard it only comes with a 350w PSU. Not sure of any of the other specs or make and model of PSU. My question is what can this PSU possibly run reliably and for how long. I take it it's probably a OEM case with built-in PSU. I still told him first to get a quote so I could see if it was worth it, but no some people just don't listen and they will just have to bump their own heads.


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## Tyree (May 10, 2009)

350W is no where near sufficient for any modern day PC. We can't advise on a proper unit without knowing the specs of the PC.


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## Johnny1982 (Oct 15, 2010)

Tyree said:


> 350W is no where near sufficient for any modern day PC. We can't advise on a proper unit without knowing the specs of the PC.


That's exactly what I thought. Can't believe these Computer "Salesmen". I'll try getting info on the build not sure if I can get it though. But crumbs when I bought my 2nd PC it came with a 450w PSU bare minimum I would of thought. Didn't think they still make 350w anymore. My first PC came with a 300w PSU but that only ran a Celeron 2,4ghz (Old Pentium 4 type) and an AGP Radeon 9250 which doesn't use so much power, anyhow I sold that on to someone else. The first thing I thought about, if this guy wants a better GPU then he has to first replace the PSU.


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## Tyree (May 10, 2009)

We suggest a minimum 550W good quality PSU for any PCI-E GPU.


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## Bill_Bright (Dec 17, 2004)

> Hi guys, a little while ago I inquired about a basic PC that could support FullHD


I am afraid I have to put a different tact on this and disagree a bit here. What is this computer used for? Does it use on-board graphics? 

Note with today's much more efficient CPUs, DDR2 or better yet, DDR3 RAM and on-board or conservative HD capable graphics card, a good quality 350W PSU from a reputable maker is more than enough horsepower to run MS Office, read and write email, surf the Internet, do on-line banking, and to watch an occasional DVD or BluRay disk in FullHD. More than enough! The demands for more PSU horsepower with today's hardware comes when using monster CPUs, massive amounts of RAM, and most importantly very power hungry graphics cards. If this computer is using on-board graphics or a conservative card, has 4 sticks or less of RAM, and no more than 2 HDs and an optical drive, then I bet my reputation a good quality 350W supply from a reputable maker is plenty. How can I do that? Because high-end HTPC and media center PCs are being integrate into home theater systems all the time these days. Many use "low-profile" PSUs to fit in microATX and ITX cases and these low profile PSUs are typically 300W or even less and do an outstanding job of meeting power demands. It takes very little graphics horsepower to "view" videos or HD (1080P) TV content through a computer, or surf the Internet or do "Office" tasks. Likewise, today's Intel i3, i5 CPUs or AMDs equivalent can process such tasks much more efficiently than their predecessors, barely breaking a sweat. Most computers made in the last 2 - 3 years do not have the power demands of computer made before that. I say most because there are extreme exceptions of course. Gaming rigs with two hefty graphics cards, 8Gb or more of RAM, several HDs, and high-end CPUs may need 750W, 850W or more. But motherboard makers, DDR3, HD makers, CPU makers and even Windows 7 are all doing much to make computers "green" - or at least greener than those of just a few years ago. 

Note too that no notebook power supply generates more than 300W and some come with very capable HW. A notebook (albeit with a "mobile" CPU) typically consumes 150W or less. 

So if your dad's friend is a hardcore 3D animated gamer, or is doing super high-rez graphics editing, or computer aided design/engineering, then he will need a very powerful graphics solution and a larger PSU to support it. But if not then that 350W, if good quality, is probably just fine. 



> My question is what can this PSU possibly run reliably and for how long.


Sure! But again that depends on the quality of the PSU - and the quality of power from the wall. How long? For years and years. 

The amount of power a PSU is capable of delivering has nothing to do with reliability of the PSU or it's lifespan, assuming the demands placed upon it are not causing undue strain. Power does not equal quality or visa versa. 

I do agree 100% with Tyree in that we need to know what hardware we are dealing with and the intended use of this system before specific advice can be given. And I also must add that it is typical for case sellers to toss in generic, off-brand PSUs just to make a case sale. Even with top quality cases. So all of my comments above assume a good quality PSU from a reputable maker.


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## Johnny1982 (Oct 15, 2010)

I've asked my dad to try and get the sales invoice from the guy so I could review it and I'll post it up here. I've noticed here in South Africa we got this franchise computer store called "Incredible Connection" and was on their website the other day and saw that their cheaper PC's, like a all-in-one system only ships with a 220w PSU. To me that's crazy!!!! I've got a E2160 o/c'd to 2,7ghz and a HD4870 and I was advised to get a Corsair 750w PSU. Granted my PC is probably not so "Green" as the latest models as it still uses some old technology, but I'll rather be safe than sorry. I currently have a Gigabyte ODIN 585w PSU. Here's a link to one of the PC's with a 220w PSU: http://www.incredible.co.za/ProductDescription.aspx?SKU=69630.


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## Tyree (May 10, 2009)

As with most all prebuillts, that PSU is not sufficient to power that PC. 
Newer PC's generally require more power than the older technology.
I use no less than 550W in any of my basic builds (insuring suffient clean power for upgrades) and larger when the hardware requirements require an increase.


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## Johnny1982 (Oct 15, 2010)

Tyree said:


> As with most all prebuillts, that PSU is not sufficient to power that PC.


Totally agree. I had a Celeron 2,4ghz with a Radeon 9250 AGP card 6 years ago and even that came with at least a 300w PSU. Can't believe they get away with a puny 220w PSU.


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## Bill_Bright (Dec 17, 2004)

> Can't believe they get away with a puny 220w PSU.


Now wait you guys! We have to look at what's going on here. Look at that link again. That's a NetPC with a miniITX motherboard and Atom220 integrated CPU (most likely direct soldered to the motherboard), integrated GPU, only 1Gb of RAM, a card reader and a DVD writer. Plug all that into a decent PSU calculator like the *eXtreme PSU Calculator Lite* and you end up with a minimum of 81W and a recommended of 131W. Compensate for full loads and 30% capacitor aging and you still only get 168W recommended. So for that specific computer, a 220W PSU is plenty big, with headroom to spare. And note I used 2 x 512Mb of DDR2. With just 1 x 1Gb of DDR3, it drops to 159W. 

It is important to have some headroom in a PSU, but you don't have to have several hundreds of extra watts. PSUs do not have a linear efficiency range. They tend to have a bell shaped efficiency curve that typically peaks between 70 and 90% utilization. So running running a 350W supply when you only need 168W causes the PSU to run way out of it's peak efficiency range - noting too that 168W is when the computer is running maxed out. 

Buying too big of a PSU does not hurt anything (except your wallet) because the computer will draw from the PSU only what it needs. But if the demand on the PSU is not within its peak efficiency range, the big PSU will draw from the wall a lot more than a properly sized smaller PSU - another hit on your wallet. And as long as the smaller PSU is not under stress from too big of a demand (i.e.; heat) it will provide all the necessary clean power the computer needs, 24/7/365.



> As with most all prebuillts, that PSU is not sufficient to power that PC.


I disagree 100%. If those PSUs were not sufficient, they would be failing right and left, forcing the makers to replace them under warranty - and for that reason alone, they are not going to let that happen. 

The problem is, the PSUs that come with prebuilts typically are just barely sufficient for the demands of the computer as configured out-of-the-box. In other words, they leave virtually no headroom to add a couple sticks of RAM, another drive, and certainly not a beefier graphics card.


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## Drenlin (Dec 13, 2010)

^ I dunno, most Asus and some Dell XPS units I've seen (probably more) have Delta PSU's that should be sufficient to add a low-mid range GPU. The 350W Hipro units you see so often are even capable of low-mid gpu's...I'd figure up to about a 60W card should be ok, though obviously that's not ideal. 

Agreed, though...OEM units do usually have awful PSU's. I'm surprised they haven't continued using the old Bestec ones as much as they used to.


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## Bill_Bright (Dec 17, 2004)

It really is not about the quantity of power, but the quality of power. I would take a 350W Antec over 450W Hipro or DEER any day of the week.


> I'm surprised they haven't continued using the old Bestec ones as much as they used to.


They probably cost $1 more each!  That may sound ridiculous, but when Dell and HP buy 100,000 at a pop, that's $100,000.


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## Johnny1982 (Oct 15, 2010)

Here are the specs of the PC involved taken directly from the invoice:

Case + PSU: Gigabyte P2 300W 4-in-1 Black Computer Chassis
Mobo: Gigabyte G41M-Combo DDR3 & DDR2 Motherboard
CPU: Intel E5500 2.8Ghz Pentium Dual Core
RAM: 2x 2GB Transcend DDR3-1333 Memory Modules
HDD: 1x Seagate ST3500418AS 500GB HDD SATA
DVD: LG Internal Super Multi DVD Rewriter 22x
GPU: Sparkle Nvidia Geforce 8400GS 512mb PCI-Xpress
OS: Windows 7 Professional 32bit

Hope this info helps.


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## Tyree (May 10, 2009)

We strongly suggest a 550W minimum good quality PSU for any PCI-E GPU.
Anything less can lead to problems down the road.


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## Johnny1982 (Oct 15, 2010)

Sorry Bill_Bright I'll rather stick with what the TSF moderators suggest. Granted I see that it is a miniITX Motherboard, my bad.


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## Tumbleweed36 (May 14, 2005)

Johnny1982 said:


> Sorry Bill_Bright I'll rather stick with what the TSF moderators suggest. Granted I see that it is a miniITX Motherboard, my bad.



Wise decision. It is called either pay for a decent sized power supply now or pay later and have to purchase another one when the weak one tanks. No sense in having to do this two times.


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## Bill_Bright (Dec 17, 2004)

> Sorry Bill_Bright I'll rather stick with what the TSF moderators suggest. Granted I see that it is a miniITX Motherboard, my bad.


Sadly, the point is being missed here. First, let me say that I agree 100% with the staff and others here that a quality PSU is _absolutely essential_ to ensure stable operation with today's high-speed digital electronics. I have always been an advocate of quality power (and a good case) as the foundation of any good computer. 

My concerns here are the applications of blanket statements. There are 3 scenarios being discussed in this thread and blanket statements about 550W PSUs and OEM PSUs are incorrectly being applied to all 3. It does not matter if you are a MS MVP (link included just to point out I've got a little experience in this field), Moderator, admin, certified technician or total newbie - blanket statements cannot be applied to all scenarios and remain true, or practical. That's just not reality. There are just some things that must be considered on a case-by-case basis and the selection of the PSU is one those situations. 

*Scenario 1. Mini computers* - You agree with the 550W blanket statement while understanding the example was a miniITX computer. I accept that and defend your Right to your opinion. As I noted before, too much PSU won't hurt anything but your wallet. But I showed that a 550W supply is way overkill for that THAT specific miniITX computer. That means that PSU will not be running at peak efficiency - again, hurting nothing but your wallet. However, note that many ITX and µATX systems come in ITX and µATX sized cases and they simply will not support normal sized ATX standard PSUs. You MUST use a low profile PSU and there are very few low profile offerings over 350W and I doubt you can find one that is 500W, or greater. 

As I noted, many folks - including very discriminating audiophiles and videophiles are integrating HTPCs into their home theater systems. These folks are not going to put cheap, noisy (audibly or electrically) underpowered PSUs in their HTPCs or HT equipment racks. HTPCs do not need monster graphics solutions or powerful CPUs to pass HD or BluRay video content and surround sound to a big screen TV and A/V Receiver. The same applies to plain old office machines. Many of these systems use a good quality low-profile, 300W supply that works perfectly in those scenarios. 

Note the excellent ATI HD5570 1Gb PCIe Low Profile DirectX 11 card consumes less than 45 watts under a full load. Couple that with an efficient i3 or i5 CPU or AMD equivalent, a SFF motherboard, and you might touch 200 watts. NO WAY do you need a 550W supply for that. It is just not realistic, or practical. Therefore, the blanket statement does not apply here

And once again, low power does not automatically mean low quality. 

*Scenario 2. Pre-built Computers* - NO DOUBT pre-built PC suppliers (and many "good" case retailers :sad use cheap, generic, and barely adequate PSUs in their builds that leave little to no room for future expansion. This is just one reason I've been building custom PCs since 1991. I have stacks of never used cheap PSUs I pulled from good cases because _I firmly believe quality power is essential for stable performance_. But the fact Dell, HP, Acer and many others put those barely adequate supplies in their computers does NOT mean "_the PSU is not sufficient to power the PC_." I am sorry and with all do respect to the TSF moderators, that is simply a false statement. If there was not sufficient power, these PCs would not last past day 1, let alone the warranty period or beyond. There are millions and millions of Dells, HPs, Compaqs out there in offices and homes that have been running for years and years on their OEM PSUs - and many of these machines have never been opened and cleaned. 

*Scenario 3. Custom built PCs* - Sadly, many inexperienced or very budget-conscious builders will attempt to save a few bucks by going cheap on the PSU. This is typically a mistake and I agree with the TSF staff here that a poor choice here when buying your components can lead to problems down the road. Therefore I agree that 550W for mid and full size towers, assuming a quality supply from a reputable maker is probably a good minimum, _if you are uncertain about your future upgrade plans_. This would be true even if using a µATX motherboard, which most mid and full tower cases should support, with integrated graphics and a modest CPU. While those components don't need near that much power, it leaves enough headroom to add more RAM and a decent graphics card down the road without having to replace the PSU. So no disagreement there. But I also contend that a quality 400 or 450 watt supply would likely provide years of service while at the same time, operate at or closer to peak efficiency thus saving money during the initial purchase, and every month thereafter when the electric bill comes due. 

BTW, how many high powered notebooks, many of which have high-end PCIe graphics solutions, lots of RAM and powerful CPUs, have you seen with 500W or greater power supplies?

So to be clear - I agree 100% that a quality supply with adequate power is essential. My issue is with blanket statements about "most pre-builts" and 550W minimums for "any PCIe GPU". The only blanket statement that applies to PSUs is to get a quality supply. The capacity must be determined by the specific, or anticipated future needs or you simply waste your money and energy consumption by buying too big. 

Johnny1982 opened this thread with the question,


> "what can this [350 watt] PSU possibly run reliably and for how long?"


The answer is it can run just about any entry to mid level PC for many, many years - assuming the PSU is well made. 

Finally, using the specs of the PC listed in post #12 above (except the e5500 was not listed so I used the e6500 from the same CPU family) and setting system load to 100% (although that is not realistic in the real world) and adding a 120mm case fan, the eXtreme PSU calculator comes up with 191 minimum and 241W recommended. Setting capacitor aging to 30% to account for anticipated and natural degradation over years of service, it comes up with 248W minimum and 298W recommended. So that 300W supply that comes with that pre-built, while not likely to support future upgrades, is plenty sufficient to provides years of reliable service - again, assuming the supply is well made.


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## Tyree (May 10, 2009)

Tumbleweed36 said:


> Wise decision. It is called either pay for a decent sized power supply now or pay later and have to purchase another one when the weak one tanks. No sense in having to do this two times.


Ditto ^


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## Bill_Bright (Dec 17, 2004)

I appreciate the loyalty you all show for each other, but none have presented any evidence to justify the blanket statements. 

Note there is no disagreement that a quality supply is paramount, and certainly, if you are building or upgrading your own computer, planning for the future is not in question either. So if anyone can show where anything I said was inaccurate, I will humbly admit I am wrong.

I fear what has happened is a distinguished contributor made these statements years ago, and they just stuck, and have since simply been repeated, cited, repeated and cited again. But the facts are DDR2 is 20 - 30% more efficient than DDR, and DDR3 is 20 - 30% more efficient than DDR2. This results is less power consumption per stick of RAM even though the speed and capacity of these sticks multiplied several times over. CPUs typically used to consume 90 - 130w of power while today, many consume 65W and less. Motherboards are more efficient and at the same time, pack more and faster features. Granted, high-end graphics cards still consume massive amounts of power (they do after all, have more transisitors on die than the best CPUs), but most people do not need or use high-end graphics cards. And more and more performance cards are efficiency conscious too. 

So the facts are, today's computers have better performance while consuming less power (and generating less heat - which is wasted watts) than those of just 3 - 5 years ago.

I am truely sorry if I have ruffled any feathers, but the status quo only last a couple days in this industry and today's eco-friendly environments. Again, if anything I have presented is wrong, please show us how.


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## MPR (Aug 28, 2010)

Efficiency graphs for modern PSUs _are _bell-shaped but the ones I've see are also quite platykurtic (i.e., fairly flat). If one can assume that PSU manufacturers' reporting of their 80-plus certification levels is correct then the Gold certification requires 87% efficiency at 20% load, 90% at 50% and 87% at 100% load, not a very steep drop-off on either side.

Looking actual graphs of efficiency in testing by reviewers it doesn't seem that the PSUs always reach the stated efficiency but this is because the reviewers (at least those with the proper equipment) often test under more "real-world" conditions of temperature. As you say, "Heat is the bane of all electronics!"

I do hold a CET but only build computers as a hobby (my main vocation is biology instructor) and admittedly don't know as much as most of you here. However, from personal experience every time I've upgraded a HP, Dell or other store-bought computer for a friend or family member with additional memory, CPU and/or video card I also had to upgrade the (usually 300 W or so) power supply. Some computers would tick along fine sending e-mails and viewing photos of grandkids until one of said grandkids tried to run a moderately-system-intensive computer game.

I would think that you would not get a huge decrease in efficiency on the low end unless you, say installed a 1000 W computer in a system calculated only to need 300 W. If the charts are to be trusted the supply I have (Corsair AX850) actually hits its peak efficiency at around 425 W, or exactly half its rated capacity.


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## Bill_Bright (Dec 17, 2004)

Good point about the 80 Plus certifications, they do have a fairly flat efficiency rating. I always recommend buying 80 Plus supplies in my canned text on selecting PSUs, so I was remiss in not mentioning that earlier. Of course, Gold Certified PSUs are not considered "budget" supplies and at nearly $200, neither is that AX850 Corsair, one of my brands of choice. And yes, according to the Plug Load Solutions Report for that PSU, it does reach peak efficiency at 50% power. But it should be noted the difference between the peak and low points appears to be just over 3 percentage points. 87.82% is still an excellent score. So my point earlier about buying too large will cost you more every month in energy costs due to inefficiencies, at least with good quality PSUs, was not accurate and I apologize for that. An extra big PSU still costs you more initially, however. 



> from personal experience every time I've upgraded a HP, Dell or other store-bought computer for a friend or family member with additional memory, CPU and/or video card I also had to upgrade the (usually 300 W or so) power supply.


Yeah, all the more reason to build your own. Then you can plan for future expansion. 

The good news is those makers no longer use proprietary PSUs so if you do decide to upgrade one of those store-bought computers (if made in recent years) you can buy a commonly found ATX standard supply instead of being forced to buy another proprietary supply.


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## Tyree (May 10, 2009)

PSU makers can "claim" any statistics they want. Many lower quality manufacturers use very low temps to accomplish there power ratings.
Stay with top quality hardware, like the brands we recommend, and those issues aren't a concern. :grin:


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## Bill_Bright (Dec 17, 2004)

> PSU makers can "claim" any statistics they want.


Well, they can't claim 80 Plus certifications unless they earned it. And to earn it, they have to submit these power supplies for testing. If the supply does not meet the requirements, the maker does not get to put the 80 Plus moniker on the product.


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## gcavan (Aug 13, 2009)

They can, and do. Doesn't make it so. It is an acknowleded problem that there are some power supplies in the market carrying fake 80 Plus badges.

You can confirm your chosen power supply has a legit 80-Plus cert at the Ecos Plug Load Website

In any case, the 80 Plus cert is based on an operating temperature of 23C. The only time any power supply is at that temp, it is turned off.


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## Bill_Bright (Dec 17, 2004)

> In any case, the 80 Plus cert is based on an operating temperature of 23C. The only time any power supply is at that temp, it is turned off.


 Sorry, but that too is incorrect. Please note the Test Protocol in the link you provided. On page 21, Paragraph 5.6, it clearly states,


> *5.6 Test Room*
> As is specified in IEC 62301, the tests shall be carried out in a room that has an air speed close to the UUT of £ 0.5 m/s, and the ambient temperature shall be maintained at 23°C ± 5°C throughout the test. There shall be no intentional cooling of the UUT by use of separately powered fans, air conditioners, or heat sinks. The UUT shall be tested on a thermally nonconductive surface.


The "ambient" temperature shall be 23°C, not the "operating" temperature of the PSU. That's a huge distinction. 23°C = 73.4°F, which is quite reasonable.

Plus, I don't think any reputable PSU maker is going to put an 80 Plus, Energy Star, Windows 7 Ready, Crossfire, SLI, etc. sticker on their box.


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## Tumbleweed36 (May 14, 2005)

Unfortunately, some do use 80+ certs on power supplies that do not meet those standards so one has to check to make sure. We all know that any reputable  power supply company would not do that, but the average consumer doesn't know which companies might be reputable or not...gosh, most would not even know how to check.

That being said, this back and forth banter concerning who might know more an issue than someone else, more hands-on experience etc., know more about what is correct and what is not, serves no useful purpose to the OP's original question. We are so far off track now that the conversation has no relation to the original question.

Therefore, I am closing this thead since it serves no useful purpose.


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