# The myth of needing high wattage pc power supplies.



## That Guy (Aug 19, 2017)

But add a ton of USB devices, maybe a hard drive or two, a better graphics card, more ran, maybe an accessory card down the road, 1 or two rom drives... and viola! you have a bigger load... 500watt is more of a future proof idea...

Especially if you want to add a second graphics card... say (2) 970's or (2) 1080's


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## Guap0_ (Dec 2, 2017)

Maybe pushing the limit isn't necessary but I've seen a better performance with higher watt power supplies.


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## Fish_Stick (Feb 28, 2017)

While most are overbuilding I would even question your setup with only a 380W if the efficiency wasn't great. Based off the specs and maxes, a 250 gts can pull a max 150 W from Nvidia. (https://www.geforce.com/hardware/desktop-gpus/geforce-gts250/specifications) add in a 125W processor max and you're already at 275 without accessories. Add in another 20-30 watts for hard drives and another for fans and you're right at the limit where efficiency will determine if your system is stable or not. Alot of folks buy bigger though for expansion into SLI and heavy overclocks.


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## user_12345a (Nov 23, 2014)

The processor is actually rated 95w, not 125w.

Video card is power hungry; not even into games but it was only a few bucks more than a basic used card.

it's a quality 80plus psu.

No sli, no overclocking. 

I was nervous about it, putting these parts (used) in but it's handled the load just fine.

All devices will never be drawing peak rated wattage at the same time. 

Also if you look at benchmarks where part of the testing is power use, the plug load never comes close to the typical power supply size.

The plug load is significantly more than output. they're rated based on output.

People put safety margins on top of safety margins and then end up with a 600w+ power supply for a machine that never draws more than 250w.


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## Red Squirrel (Jun 29, 2009)

Graphic cards are what seem to use tons of power now days. A couple hundred watt from a single card is not unheard of. I did a SLI system and I was pulling about 400w from the wall. I did mistake the power requirements of the cards though and went with a 1000w psu, could have gotten away with like 750w or so. 

What's surprising is how little power business class small form factor machines use. Like under 100w.


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## That Guy (Aug 19, 2017)

reminds me... LOL I gotta remove the 1200 watt PSU from my tower and put the 750 back in as I no longer run with 10 hard drives, and wont be doing 3 way SLI like I was originally planning to do... largely thanks to data mining.


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## JasperST (Sep 7, 2012)

I built a htpc and use a laptop battery charger for the power supply. Onboard video but does hd with no problem.


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## Bud9051 (Nov 11, 2015)

My electronics is 40 years behind the times but I enjoy reading threads like this just to remind me of how much things have advanced, but one thing I did not see mentioned is heat. All electronic failures are due to heat, on the board or inside a chip. If a power supply is rated at 250 w then there are heat sinks and components in there that are running at their maximum temperature at that capacity, at the surrounding temperature. A 500 w unit would be cruising well below its max temp with larger heat sinks and larger capacity components.

Somewhere inside that power supply is its hottest spot (and highest risk of failure) and selecting one with a higher capacity will most likely lower the temp of that hot spot. Think of it this way, what happens to the power capacity of any power supply if its cooling fan (or air flow) dies?

Bud


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## Fish_Stick (Feb 28, 2017)

user_12345a said:


> The processor is actually rated 95w, not 125w.
> 
> Video card is power hungry; not even into games but it was only a few bucks more than a basic used card.
> 
> ...


With a 95W TDP that gives you some overhead. Plus not playing games on it makes a big difference since your graphics card will really only be idling most of the time. There are some problems though that the article linked below explains. Basically even though some ps are rated at 500 watts, they don't provide enough amperage on the 12V rail for gpus. So you end up with a cheap 750 watt psu because you needed a little extra on the 12V rail. Just like everything else, people have cheaped out the units and end up with garbage. I remember when I was building it was a $100 for a quality psu and you didn't have any issues with them. SeaSonic and Enermax were already 80%+ which was great for the time. Now people spend $50 for the case and psu and wonder why nothing works right. 

http://www.tomshardware.com/reviews/geforce-radeon-power,2122-6.html


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## user_12345a (Nov 23, 2014)

The quality of the unit you buy has more to do with heatsinking and temperature ratings than wattage.

Also same with amp ratings for the 12 amp rails.

There's no way a $30 psu rated at 500w will reliably put 400 to 500w. most will probably crap out and have issues maintaining stable voltage above 300.


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## supers05 (May 23, 2015)

user_12345a said:


> ...
> 
> There's no way a $30 psu rated at 500w will reliably put 400 to 500w. most will probably crap out and have issues maintaining stable voltage above 300.


Believe it or not, mass production and super cheap electronics make that possible. (it's also the biggest reason people use 450 or 500w psus. Simply cost.) No, I wouldn't ask it to output 500W, I'd only expect it to peak at that level. I would expect voltage stability issues above 400W, but that's ok. 300W would have a real safe level, but most el-cheapo PSUs can do better then that. 

..

Now it's really easy to determine what psu you need. Take all components, add up their power requirements. Add 20%. (You really don't want to be at max, as their best efficiency is typically around 80% rated load.) Double check that power requirements on all rails will do. Voila. 

I've clocked my computer at 900W. With the monitors, speakers, etc, I've run over 1300W at the UPS. (main reason why I only have 2 GPUs, the UPS wasn't big enough.) I'm not only a gamer, but like to video edit from time to time. 

I used to build computers in a previous life. Yes, it's a shame that many "professionals" out there know so little about the tech details, but any industry is like that. Some are awesome, some are not, most are just mediocre. 

Cheers!


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## user_12345a (Nov 23, 2014)

ust realized by looking at ratings...

The cheap ones have very weak 12v rails. Over 50% of of the wattage is calculated from the 3.3 and 5v rail ratings.

The large power consumers like gpus, cpus, motors draw from the 12v rail and the regulating components drop it down; 3.3 and 5 mostly run the lower level electronics.

My 380w has better 12v rail amp ratings than most el cheapo 500w units.

Plus good heatsinking, power factor correction, filtering for stable output.

It's like having a 200 amp electrical service for a house but only up to 50 amps of that can be 240v circuit.



> Now it's really easy to determine what psu you need. Take all components, add up their power requirements. Add 20%. (You really don't want to be at max, as their best efficiency is typically around 80% rated load.) Double check that power requirements on all rails will do. Voila.


I just use the online calculators and only use quality units with decent 12v rails.

but i don't build them completely any more, just keep what i have running.


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## raylo32 (Nov 25, 2006)

Modern CPUs and SSDs really reduce the power needs. Unless you are running one or more monster graphics cards a good quality mid size power supply is best. I have a current i7/SSD build running 24/7 streaming and recording 6 security cams, mostly 720p and 1080p, using the Intel onboard graphics. It pulls way less than 100 watts. When I stream Netflix or something else simultaneously it goes a bit higher.


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## Jgp267 (Jan 31, 2018)

I always go higher so I'm not pushing the supply to the limit. The only one I had go out in 25 years was an EVGA that worked for five minutes sparked and took out my motherboard. And I've never had a problem with Antec.Have 5 computers that have been running 24/7 for almost 10 years. The Antecs in each are still going strong. 

Sent from my XT1635-02 using Tapatalk


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## tom_poconos (Nov 6, 2017)

They're needed for tandem graphics cards (called SLI or Crossfire mode). When you play a game on max settings with 2x high-end cards you'll turn your PC into a small space heater - hence the need for the 1000W PSU's. Obviously the vast majority of people don't need them. Only gamers and other high-end graphics enthusiasts.


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## user_12345a (Nov 23, 2014)

I've never understood sli, surely today's cards should be powerful enough for one to be sufficient.

it always sounded like a way for the industry to sell more video cards whether needed or not.


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## tom_poconos (Nov 6, 2017)

user_12345a said:


> I've never understood sli, surely today's cards should be powerful enough for one to be sufficient.
> 
> it always sounded like a way for the industry to sell more video cards whether needed or not.


Yup, even some gaming laptops can run a lot of games at max settings.


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## supers05 (May 23, 2015)

user_12345a said:


> I've never understood sli, surely today's cards should be powerful enough for one to be sufficient.
> 
> it always sounded like a way for the industry to sell more video cards whether needed or not.


I run 2, my friends run 3 and 4 cards. Yes you can get the best of the latest and due mostly with 1, but it doesn't take long before you see games outstrip your capacity. Older video card are much cheaper then new ones these days, thanks to cryptocurrency. You can buy 4 older cars for less then a new card.

I used to be into video editing. Now it's just games. 

Cheers!


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## user_12345a (Nov 23, 2014)

Except the power use of running 2 to 4 cards is very high. the power cost can add up very fast.


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## supers05 (May 23, 2015)

user_12345a said:


> Except the power use of running 2 to 4 cards is very high. the power cost can add up very fast.


If you don't pay for electricity, that doesn't matter. They only draw that when running, so it's more of a cost / use rather then a capital cost, which not everyone has. 

Either way, getting your hands on a decent video card these days is rather difficult. They are going for 2 - 3x msrp if available at all. 

Cheers!


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## user_12345a (Nov 23, 2014)

Depends on the definition of decent is, lots of video cards available for $200 or less.

Most pay for electricity even if renting, it's only very few rentals that still have not yet put in sub-metering.

The wattage of have 3 to 4 gpus vs idling vs 1 I bet is very high compared to everything else in a pc, unless they're capable of shutting down. Most of the time, it's like being in slow traffic, comparing running a 4 cylinder vs a 12 -> which is going to burn up more fuel when the hp isn't actually needed.


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## supers05 (May 23, 2015)

user_12345a said:


> Depends on the definition of decent is, lots of video cards available for $200 or less.
> 
> Most pay for electricity even if renting, it's only very few rentals that still have not yet put in sub-metering.


You're referring to Ontario, only a subset of the world. 

Anything less then a card at roughly $4-600 msrp won't do much for modern gaming. (ball parking of course) You'll be running in potato mode. Anything that is sub $200 at this time is next to worthless. Even my fairly old cards cost that. (Everything doubled in November -December. There's a global shortage of cards.) 

Cheers!


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## user_12345a (Nov 23, 2014)

Good thing I'm not into gaming then, you can by a whole computer for $600.

I spent under $150 on this upgrade with used parts - board, chip, ram, vid card. 

you're saying the 250 gs i put into this machine is worthless, was hoping it would suffice for the odd game or two. haven't tried. was only a little more than the basic card.


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## supers05 (May 23, 2015)

user_12345a said:


> Good thing I'm not into gaming then, you can by a whole computer for $600.
> 
> I spent under $150 on this upgrade with used parts - board, chip, ram, vid card.
> 
> you're saying the 250 gs i put into this machine is worthless, was hoping it would suffice for the odd game or two. haven't tried. was only a little more than the basic card.


Did you mean the gts 250? It only has a texture fill rate of 47 GT/s and 387 GFLOPs, My ancient cards do 60 GT/s 2.2TFLOPs each, and I can push them both past 75% on some more basic games. (crossfire mode) 

Cheers!


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## user_12345a (Nov 23, 2014)

https://www.geforce.com/hardware/desktop-gpus/geforce-gts250

At the time of release, around 2010 it was a good mid range card capable of doing everything and i got it based on that. figured better than a simple used card with a 64 bit memory bus.


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## supers05 (May 23, 2015)

user_12345a said:


> https://www.geforce.com/hardware/desktop-gpus/geforce-gts250
> 
> At the time of release, around 2010 it was a good mid range card capable of doing everything and i got it based on that. figured better than a simple used card with a 64 bit memory bus.


It's good for basic games or average games in potato mode. You might not be able to launch the latest games. (Nvidia does better in back supporting though, so it might crawl through the game.) 

It's no good for mining so it's still available online. I see it going for $30 on fleabay. 

Cheers!


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## user_12345a (Nov 23, 2014)

yah it was ebay.

off to google "potato mode"


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## supers05 (May 23, 2015)

user_12345a said:


> yah it was ebay.
> 
> off to google "potato mode"


Lol. Graphics at minimal settings. Everything looks like giant potatoes. At least to some people. (Ultra low shader and texture quality is the biggest offender.) 

Cheers!


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