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What happens if you go over your computer's PSU watts?

by dat1asiandude / July 12, 2006 1:28 PM PDT

Like for example, if you have a 250 watt power supply and you add in a new graphics card that made the computer go over 250 watts, then what happens to the computer?

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Possibilities. See pictures at link.
by R. Proffitt Forum moderator / July 12, 2006 1:40 PM PDT
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(NT) (NT) LOL! That first picture should be a deterrent!
by linkit / July 12, 2006 1:45 PM PDT
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Not only can that happen but I've seen...
by R. Proffitt Forum moderator / July 12, 2006 1:52 PM PDT

The entire PC wiped out as the power supply sputtered and died under too much load. They lost it all.


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Typical symptoms
by Stan Chambers / July 12, 2006 2:05 PM PDT

As Bob indicated, the results can be disastrous. However, the typical symptom is shutting down for no apparent reason, then rebooting. Note that rebooting during operation may also be a result of overheating.

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Oh no!
by Willy / July 13, 2006 2:04 PM PDT

Depending on the quality of the psu, it will last as long as it can. Sooner or later it will fail. Not only will you lose the psu, but the possibility exists you may take some other componet(s) with it, so beware. PLUS, the possibilty of a "fire" can happen so don't push it, I seen some pretty black and smelly blown psus, thus get a replacement when you know you need it, ASAP.

tada -----Willy Happy

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What happens 1st question
by rochagomes / July 13, 2006 10:44 PM PDT

You never stated...how much over. 10 watts/20 watts?
A good chance maybe nothing. 50 watts or more....as everyone stated....buy a new supply or return that graphics card.

Everything electrical is usually conservatively rated.

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"Everything electrical is usually conservatively rated."???
by R. Proffitt Forum moderator / July 13, 2006 10:49 PM PDT

Read the link I provided. 9 out of 21 units failed to meet the labeled ratings.


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Unfortunatly, all too common.
by DrMicro / July 14, 2006 1:24 AM PDT

I see problems like this very frequently, usually with low-end OEM PC's that the user has gotten disgusted with the crappy performance or lack of installed features and decide to "upgrade the old girl". PC store salesmen rarely, if ever, inquire, advise or are even aware of the PSU capacity of the customers computer; they're just happy to send you out the door with a new fancy graphics card, a dual-layer DVDRW, an extra stick of RAM or two and maybe a second or larger hard drive to boot. Double the risk if the computer user decides to light up his or her case like the Las Vegas Strip. Rarely, if ever, is any thought given to the the rating of the PSU during the DIY upgrade process. For that matter, we've seen customers computers that were upgraded by PC technicians who ought to have known better but obviously didn't.

Given a constant mains power, more load means more current draw. More current draw means more heat. The PSU struggles to keep up and the voltage on the rails drop. Less voltage with the same load means even more current and more heat until something gives. If you're lucky, it'll ONLY be the PSU, but we've seen fried CPUs, Motherboards, Memory, individual cards, all damaged due to an overloaded PSU.

Most low-end OEM machines do not have large or very high quality power supplies. They are designed to handle the load of the machine (or at least we hope so) as it originally came from the factory and not much more. At $299 for the weekend or holiday special from Dell (and a free printer besides!), how much PSU quality do you think you're really getting?

Now that I'm done ranting, to answer your specific question, I would strongly advise you to replace your PSU with a good decent-quality unit with a rating somewhere between 300-350 Watts. You have to bear in mind, as Bob alluded to, that PSU units often do not live up to their billing, and often are rated at peak load, not constant load. Thus, your current 250W PSU may only be putting out 150-200W under constand load.

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Also looking into buying graphics card, still confused.
by firebad / February 13, 2012 2:41 AM PST

Alright, I have a 300W PSU, and there is a graphics card which says minimum wattage 300W PSU.
my computer is the acer aspire
<div> (

http://www.superwarehouse.com/Acer_Aspire_M3410-UR21P_Desktop/PT.SGDP2.002/p/1650656 ) </div>and the card is
<div> (

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=924829&CatId=7005 ). </div>This meets every aspect I require for my computer, all the right memory types, PCI-e, everything. but I am just stuck on wattage. there is also this card

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=924832&Sku=V261-5457 ) </div>which only requires a 250 W PSU, but then again, I won't quite get the performance like I would with the previous card. I realize that this isn't just a beg for answers forum, but after a month of researching, I still don't quite have the facts that I am looking for, and am still caught between these two cards. I believe it will be safe to buy the 300W PSU demanding card, but I am also caught against the safety of the only 250W PSU requiring card. Your help, if given, is thanked greatly.

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The ATI 5450 is what we use when we can't change the PSU.
by R. Proffitt Forum moderator / February 13, 2012 2:48 AM PST

But the other card is a better card for playing games. But given how tight the PSU rating is, you have to accept the risk of losing the entire machine (see above.)

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Look at the specs on the side of the Power Supply.
by R. Proffitt Forum moderator / February 13, 2012 3:03 AM PST
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Okay so I read that article...
by firebad / February 13, 2012 5:39 AM PST

From the looks of that article, that's not the same card, but they did mention giving yourself 100 watts for a safety margin, that's all the confirmation I needed. Okay, ATI Radeon HD 5450 it is! Thanks for your help

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the obvious followup..
by jasantosr / July 14, 2006 6:04 AM PDT

... how does one determine what the PSU requirements are???

I changed the MB (ABit KT-7a RAID)
change the CPU (Athlon TBred 2100+)
overclocked it to 1978mHz
added RAM (512M, 512M, 256M)
Added disk drives (2x 160G HD, 40G HD, CDRW, DVDRW)
added I/O boards (GPU, USB2, NIC, MODEM, Audio)
added 3 fans

Now what are the requirements???

MBM is showing +12v=11.89V, 5V=5.03V
(appears to be relatively accurate per my DVM)
Wouldn't this be a good way to judge it?
If 12V <= 11.4V and/or 5v <= 4.75V then the PSU is out of spec (+/- 5%) and probably struggling.
I think the PSU is 300W.

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Remember that the PC "gulps" power.
by R. Proffitt Forum moderator / July 14, 2006 11:48 AM PDT
In reply to: the obvious followup..

So you need more on startup and other times. Add about 50% minimum to your 300 to start.


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See Link
by DrMicro / July 15, 2006 4:38 AM PDT
In reply to: the obvious followup..
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by ask4anu / July 14, 2006 2:50 PM PDT

if you use a power supply and draw more then it rated watts you cpu and motherboard will let you KNOW buy shutting down for no reason at all with out you shuting it down and you could also cause harddrive failure burn out your cpu cause bad spots on your harddrive loose data burn a componet out on your motherboard or just have sorry performance all around

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Wattage alone is misleading
by Zzan01 / July 15, 2006 3:32 AM PDT

You are not asking the right question. Adding the new graphics card may still not cause the power supply to exceed its maximum power rating but still become unstable or shutdown. What is more important to consider is the maximum ratings for each voltage output in the power supply. All other things being equal one power supply may appear to underpower a computer while another one with the same overall wattage ratings may work fine. The better one generally has higher current ratings for the 12 and 5 volt lines. It may even have a higher true wattage rating because its manufacturer uses a more conservative approach in determining the specs.

Determining the voltage and current requirements for all the components in the computer should allow someone to determine the requirements for the power supply. These numbers many times can be estimated but are not always available. These numbers are what a power supply calculator program uses to make its recommendation.

Most people either give it no thought until there is a problem or throw in a high wattage power supply to be on the safe side. Even then a high quality power supply generally runs cooler, is more stable, and is less likely to fail. A low quality 500 watt supply may even perform poorer than the 250-300 watt supply that it replaced.

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Best not to find out
by Willy / February 13, 2012 3:05 AM PST

Many times if not too much of a burden it will work until it finally bites the dust. If the demand is far too great, then immediate results will allow smoke out of the box. Many times, I have found working PSUs that were marginal but still worked. However, repeated boot-ups became the normal and upon tear down found the PSU in physical breakdown mode. I wondered how it worked as it did. So, beware if you know the limits of your current PSU and future wattage exceeds it, time to upgrade to a better PSU.

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