Power Supplies - Generic or Expensive?

The biggest wear factor on power supplies comes from the electricity supplied from the wall itself. The constant transients that occur, whether it be the small surges or brownouts that the PSU has to deal with in order for it to keep a consistant level of output to the motherboard and peripherals that are plugged into it, or its capacity to dissapate the heat generated when its powered up.  
To allieviate the first, I would also look at a well designed "line interactive" UPS( uninteruptable Power Supply) with Automatic Voltage Regulation (AVR). This would give a regulated source of power to the PSU.
The heat issue is usually tempered by better heatsinks in the PSU, most good PSU's will be heavy due to the larger heatsinks used, but the cleaner the power going in the less work for the PSU=less heat generated.
The issue of cheap or expensive is directly effected by the needs of the user. I have had cheap psu's that have lasted years, which means they survived in older less demanding computers, I have also had new expensive PSU's that have quit for no reason other than they were plugged in. I truly believe that when you put the cleanest form of power into the PSU you will get more longevity and reliability out of it.

Hello :)
http://www.jonnyguru.com/PSU/Assassin/Powmax_Assassin.html
The above review of a '500W CHEAP PSU' for $30..it doesn't even provide close to the rated power!
Quote - "As you can see from the results graph at the top of this page, I only performed two load tests on the power supply. This is because beyond 265W the power supply blew up. I let the magic smoke out."

What you will find is that 'cheaper' PSUs usually aren't honest in the specs reporting, and the components used are probably not up to standard on what it should deliver. For most normal mum/dad type computer users, these PSUs probably will be fine.

Lets look at the above PSU for example, the +12v is rated at 17A, P=VI, hence Power = 204W. CPU and newer graphics card draws its power from the +12v rail(s),
Looking at this review from example which outlines the power consumption of the cards -
http://www.xbitlabs.com/articles/video/display/evga-7900gt_4.html
eg. 7800 GTX - 80W

CPU Power Consumption -
http://www.xbitlabs.com/articles/cpu/display/athlon64-x2-3800_3.html
eg. Pentium D 820 - 130W

Using the above example, that comes to a total of around 210W to run those 2 piece of hardware (more if you take into account the hard drives etc). 500w should be sufficient yea? Nope, the +12v rail only rates a maximum of 204w (I seriously doubt it can actually even deliver close to 200w)!

Look at the Antec 380w PSU now,
http://www.antec.com/specs/NeoHE380_spe.html
If you add up all the available power - 69.3W+60W+336W+9.6W+12.5W  = 487.4w
Now why is it only rated at 380w?  That's because they actually factored in efficiency due to thermal/heat related issues.

The bottom line is, you get what you paid for. For an average computer user, a generic/cheap PSU will be fine. But if you are an enthusiast, and want to overclock/add a new graphics card/add a new SLI card etc, chances are you probably will overload/blow the relevant rails. Getting a good PSU also will give you a peace of mind that the rated specs is close to what you can expect, rather than just a number like 500w! :)

Some misc PSU reading - http://www.silentpcreview.com/article28-page3.html

*phew*, i'm tired now.. :)

I've been assembling "OEM" PCs for over the last 10 years, and like you I've only come across a couple of cases where a "cheap" PSU went "dead" (in thousands of machines!).

Usually, I also rely on the PSU that comes with the PC case box - or I get a cheap 350-450W PSU from Q-tec or similar low cost brand.

When needed/requested, I also advise the use of an AVR UPS.

The only thing I've done to my "cheap" 550W PSU from Q-tec, was to open it up and switch the fans for some more silent ones.

I would not get the very cheapest ones. once i had one of them blow in a users machine and took out the motherboard and most of the other parts inside. that was only once in hundreds of machines though.

as for the very expensive ones, i would only use that for something like a 3D workstation or DAW (digital audio workstation) that needs to run quietly and be very reliable.

Personally i usually go with the middle ground. a brand i have heard of but not the model with all the bells and whistles.

I'll weigh in on this:

I believe that there is a difference.  Over the long haul, I believe a better power supply lasts longer, as will your system components.  One has to wonder, when a chip blows on the mobo, or ram goes bad, or drives burn out, if these are a product of that particular peripheral or if it is due to the power being supplied to it.  One thing I have found in all the clones I've built, cheap power supplies do not allow for very good heat dissipation.  Some might do better than others, but when you spend a reasonable amount on a good power supply (I consider $75-$110 reasonable), it usually handles the heat better.  The case is cooler and therefore the stress on the entire system is lower.  Good power supplies (as someone noted above) also take into account and factor in efficiency due to thermal/heat related issues, therefore actually hitting their rated wattage.  Today's peripherals take quite a bit of power, everyone has tons of USB and firewaire devices they didn;t have 5-10 years ago.  Average people now do their own video editing on these machines, with multiple drives and monster video cards (with their own power requirements), and much higher CPU utilization.  Just as with other PC parts, there's no guarantee that a top brand part won't fail in a week just like a generic, but time and time again, the better parts out perform the generics as a whole.  That said, here's a few links that I believe support my arguement:

http://techreport.com/reviews/2004q4/psus/index.x?pg=1

http://www.tomshardware.com/2002/10/21/inadequate_and_deceptive_product_labeling/index.html

http://www.hexus.net/content/item.php?item=1359&page=26

Bottom line:  2 observations
1 - There are many reviews out there, at least 7-8 mentioned in this thread all pointing to better PSU's make a difference, there are far fewer one's out there saying the opposite.....where's there's smoke there's fire (or at least a burned out PSU...sorry, I couldn't help myself :)   )
2 - We spend more $$$ on better video cards, on ram that's faster even though it makes little difference except in a benchmark test, and the power supply gets the short end of the stick.  Give it it's due, get a good one for your PC.

My 2 cents...
jd

I don't really acre about the points and am not interested in providing a long discussion.

Experience has shown that decent quality power supplies are more stable and cause fewer "strange" problems.  Good power supplies can and do fail as well.  My approach is to use proven, moderately priced power supplies (ones I've had success with over the years).  Brands include Antec, Sparkle, PowerMan (Inwin), TTGI, CoolerMaster, and Enermax.

Some currently available, reasonably priced ones that I recommend:

http://www.directron.com/rs430pmsr.html   CoolerMaster 430 watt about $35.00  (a very good buy)http://www.directron.com/coolmaxv400psu.html  CoolMax 400 watt  about $25.00  (good for a cheap PSU)
http://www.directron.com/w0069ru.html   ThermalTake 430 watt  under $50.00
http://www.directron.com/ipp460q32.html  Inwin 460 watt with APC under $60.00

Note that there are no 550 watt sub $20.00 or sub 400 watt PSUs in list.

For high end systems, I recommend Antec True Power, Seasonic, Enermax, or PC Power and Cooling.

My nickel's worth:

I help a lot of local folks (mostly friends and friends-of-friends) with issues with their PC's.   The single most common HARDWARE problem is a failed power supply => and in virtually every case the failed unit was a "generic" low-cost power supply.   Coincidentally, I have two dead PC's here at the moment (an HP & a Gateway) => and the problem with both of them is failed power supply.

As you undoubtedly know, I'm a big fan of two makes:  Seasonic and PC Power and Cooling.   Personally I use Seasonics in all of my own systems => I've bought several Antec cases that have perfectly-good supplies in them; but the first thing I do is remove them and add a Seasonic.   Why??  Two words:  Efficiency and Noise.   The noise factor may not be important to many, but it's very nice to have a unit that is essentially silent.   But the efficiency factor is important:  a high efficiency power supply will waste less energy (actually saves $$);  and more importantly will run cooler => as you know heat is the enemy of reliability for your system.

Both Seasonic and PCP&C units have efficiency ratings in the 80% range, which is much higher than most other units (the lower cost units rarely exceed 70%).   This means their units will (a) use less electrical power (over time actually paying for themselves in savings) and (b) generate less heat at the same output wattage than lower-quality units (likely increasing the reliability of your system).   PC Power & Cooling has an interesting chart that compares the Turbo-Cool 850 SSI unit with an Antec True Power 550 that shows this pretty well (see #1 here:  http://www.pcpowercooling.com/technology/myths/).   One other point made in the PCP&C link is that modular power supplies are NOT a good idea => and I thoroughly agree with that as well.

In addition to the efficiency (which measures how much power the unit wastes and turns into heat), the better units also all have Active Power Factor Correction (PFC), resulting in a Power Factor of close to 1 (generally 99% or better).  This means the VA and Watts will be essentially the same => i.e. the "apparent power" reflected to the electrical source (power company) will be essentially the same as the actual power.   While related to efficiency, this is NOT the same;  but it does make a difference in both the power consumed, and in the reactive load reflected to the distribution network (i.e. it can impact other equipment on the same line).   In fact, most European countries REQUIRE power factor correction (either Passive or Active).  It's surprising to me how many power supplies have NO PFC => not just the inexpensive ones, but many mid-range units don't even have passive PFC.  I do NOT buy any units without PFC.

There ARE cases where it's not justifiable to buy a Seasonic or PCP&C => for example, the two dead PC's I have here at the moment are older units that are used by elderly folks just to do their e-mail (and in one case uses a micro-ATX PSU, which has very limited options for replacement) ... so I'll buy relatively inexpensive suppies to replace them (in one case I'm just going to donate one of my spare Antec supplies).

But for anyone building a new system ... I absolutely recommend using a high-end supply.   While it's one of those long-term savings elements that folks don't often think about, the combination of Active PFC and a high-effiency supply will most likely save $$ in the long run;  and the rock-solid power they provide is very likely to keep the system more reliable as well.

One concluding thought:  I absolutely consider a UPS with AVR a MANDATORY accessory for any PC.   Not directly related to the generic vs expensive power supply question here;  but a very important component of the overall power question.  PCs that are never exposed to unplanned power outages are consistently more reliable than those that are => and a good UPS will eliminate that exposure.

I have bought both inexpensive and expensive power supplies.  In the past, you could get away with cheap supplies because the power demand was a lot less, but nowadays, between video cards and multiple drives and power-hungry cpus, you need a minimum amount of current from the power supply.  Another consideration is the damage that a blown power supply can cause - the motherboard, video card, and hard drives are all affected to some extent by failed power supplies, and the additional expense and downtime caused by these need to be factored into the overall cost.  If the system has to be up and has to run reliably, I would go for a better quality supply to minimize risk, as well as for the aforemention reasons about heat, noise, and efficiency.  If it's for a desktop that isn't that high powered, I am willing to go for a cheaper supply, but I never go for one that has less than 18a on the +12v rail, and the cheapest one I have found that qualifies for this are Thermaltake Purepower 420's.  Otherwise, PC Power & Cooling, Seasonic, Enermax, and Antec Truepower are my favorites.  It is interesting to note that my first Seasonic blew up with a puff of smoke a few days after I installed it.  Fortunately, nothing else was damaged and the replacement unit has been working fine since.  It scared me silly when I heard the BANG and realized my Athlon64 X2 was hooked up to it!

The difference between power supply design and mother board design, is that most mother board designs are made around a common chipset that can only go together one way.  The design can't change too much except for included options (sound, video, ata, etc).

In power supply design, the components are much more varied.  With a real cheap supply, the Capacitors and coils and such may come from poor suppliers, or may be under rated.  It may not even be evil or cheating, just a misreading of the specs.  A buyer is told to get a part with a 100 rating plus or minus 10, (90-110) and a seller may provide a 90 part, plus or minus 10 (80-100) so in the end, a design that was looking for 100 may end up with 80.   Because of this, as someone pointed out above, a power supply rated at 400 watts may not actually be able to provide that power, or may not provide it on a continous basis.

The more expensive supply may not be better just because of the price, but because of the traceability.  The cheap supplies usually last the duration of their warranty, and if they don't its hard to track down the company.  This is one reason why local computer stores that are just starting up will often have lower prices, because they haven't (Yet!) had to deal with irate customers whose machines have died.  If they can't get support from the maker, the local store won't last long selling supplies that die quickly.

The more expensive supplies usually come from traceable companies who honor their warranties and must stand behind their products, so they choose parts which will fail the least.

I like Tom's HW so ditto for nobus, I also want the extra capacity up front, to handle whatever gets added later, whether I get around to additions later is besides the point, I want the capacity at purchase without a reason to have to upgrade it too soon.

Your choices other than size probably won't vary from one vendor to another, technically. It may be simple supply demand issue, or which one paid their workers less. But it does not hurt to check out, ensure that your potential cheap one is not built by someone specializing in lemons. Name brands can be welcome, wherever they are made.