25 replies to this topic

[Shahadet]

So - as I'm collecting parts for my new gaming rig (as sales pique my fancy), I'm wondering if there is such a thing as getting a PSU that is TOO big for your setup?

I'm trying to set up my 1st time rig so that I can reuse some parts in future builds - such as the case and PSU.

My current incarnation has a 750 W, 80+ gold PSU from Corsair. But due to a sale, I can grab a Seasonic 80+ Platinum, 1000 W rig for just $55 more.

BUT - this initial PSU purchase will only really be powering a regular (un-overclocked) CPU, a high end GPU (probably 7950, 7970, or 670), an SSD drive, a 1TB HDD, and some fans and a CPU cooler fan.

Would it be bad for the system and/or the PSU to have so little load put upon it? Or would it be ok?

Thanks!
-AC

[Dustin Nagasawa]

From what an electrical engineer has explained to me in the past, PSUs without a corresponding load are just inefficient and wasteful. He recommended getting a PSU about 25-30% higher than expected load, so you could expand.

[Ancalagon]

Well if you want your computer to be energy efficient and not create unneeded amounts of greenhouse gases (and making your bills more expensive at the same time), you'll probably want to get one that isn't overkill. 750W in a PSU is usually plenty for most setups; if you aren't using the extra 250W, then you'll just be wasting the $55 anyway.

Edited by Ancalagon, 07 August 2012 - 08:17 PM.

[SpookShow]

If you think its a good deal I would get it. Ive had three corsair units and two out of three failed around a year from purchase. Nothing wrong with having a spare PSU in the closet for those OMFG moments. So if its a steal get it.

[Davion5150]

Having too much PSU power isn't bad for the PS or the computer. However, it is bad for your wallet. If it was me, I would just get the 750W PS.

[Dymitry]

A psu is not a is not a power station nor an accumulator. It will ask from the line whatever is asked from the pc + dispersion (heat generated whilst converting ac to dc and voltages). Better psu = more efficiency = less dispertion = more saving. Now usually bigger psu (as in psu that needs to be able to provide reliably constant bigger wattages to the pc) needs better components hence they have less dispersion.
There is a tradeoff to be made in the buying cost of the psu and prospective savings. Spending 200£ more on a psu to save 3£ a year is not smart but to answer your question in 1 word, NO.

And seasonic rocks.

Edited by Dymitry, 08 August 2012 - 02:49 AM.

[Jack Dalton]

Save yourself 55$, grab the 750w unless you plan to SLI and OC.

Corsair is just rebranded Seasonic, so there's no issue quality wise.

[Aegic]

No.

A PSU needs to meet power consumption requirements and SHOULD have a 5-10% buffer for various reasons. This is however not required.

The PSU provides power on demand. No demand, no power. So you could have a 200000000 watt PSU and have no issues with something that draws 300 watts.

[Egomane]

Your planned setup sounds like it can be fired by a good 500 or 550 watts PSU.

Keep in mind, that most of the time during its lifetime, an average system is mostly just above idle usage of CPU and GPU.

A PSU, no matter how good it is, will come into its good performance at ~20 %. They are at their best at about 50 % and lose efficiency again somewhere above 80 %. Below 20 and above 80 % usage you are wasting power. You should plan your PSU to run at least at 20 % when your System is idle or at least not to far from that number.

A PSU always has some loss. They are never 100 % efficient!

To give you an example, I'll give you a rundown of my system.

Motherboard: ASUS Crosshair IV Formula
Processor: Phenom II X4 955 (@ 3.4 GHz)
GPU: 2x Radeon HD 5850 in Crossfire configuration
RAM: 12 GB
Harddrives: 3 HDD, 1 SSD
Optical drives: 1 Bluray burner
Fans: 6 LED Fans plus 2 Fans on CPU cooler
USB Devices: 4 (keyboard, mouse, joystick, headset)

This system is run by an Enermax Modu82+ 625 watts (230 V). Power consumption in idle is 130 watts and at maximum load consumption has been 526 watts. That was not even in gaming but burn in of the components. In games I usualy stay below the 500 watts mark. Measuring point for consumption was before the PSU at the power socket. My system wont reach the 20 % breackpoint in idle but it is as close as possible. At the top I have some power left for peaks, aging of the PSU or upgrading.

For more information you can ask the companies producing the PSUs for efficiency charts for their products. If they (the products) are 80 plus certified they (the companies) will have them (the charts) available.

Edit:
For more information, see this thread from Vulpesveritas:
http://mwomercs.com/...r-supply-guide/
I don't agree with his recommendations for the PSU sizes (I'd go lower then he does), but everything else is very informative.

Edited by Egomane, 08 August 2012 - 10:27 AM.

[Monsoon]

Well in response to your thread title, yes there is such a thing, since your wall plug is limited to 15amps, which is about 1725 watts at 115 volts.

Now the most I've recalled seeing is 1200 watts, but keep in mind anything else your plug might have installed, like speakers, lamps etc. Also keep in mind if that wall mount is sharing it's power with any other mounts throughout that room/floor.



In regards to your expanded question, just how much do you plan to have in your computer? I suppose the biggest concern will be your Video Card and if your planning to have more than one installed. If you're only going to have one Video Card, one HDD and one SSD, chances are you won't have enough peripherals to even justify the 750w PSU. The 750w would probably be more than enough to cover even a second graphic card, depending on it's energy needs.

Edited by Monsoon, 08 August 2012 - 10:23 AM.

[Catamount]

As others have noted, PSUs get horrendously inefficient at small loads. Is there such a thing as too much PSU in the sense of the system won't run? No, of course not. But there is such a thing as getting a PSU so big, you'll see no difference from using it over a slightly less overkill PSU, but you will see vastly inferior efficiency, and so the system will cost more to operate and produce more heat in non-intensive tasks (matters a lot if you're like me, and live in a place where in the summer, the difference between throwing 150W of heat into the room, and 300W of heat, means a lot to your personal comfort)

[Shahadet]

Catamount, on 08 August 2012 - 06:35 PM, said:

As others have noted, PSUs get horrendously inefficient at small loads. Is there such a thing as too much PSU in the sense of the system won't run? No, of course not. But there is such a thing as getting a PSU so big, you'll see no difference from using it over a slightly less overkill PSU, but you will see vastly inferior efficiency, and so the system will cost more to operate and produce more heat in non-intensive tasks (matters a lot if you're like me, and live in a place where in the summer, the difference between throwing 150W of heat into the room, and 300W of heat, means a lot to your personal comfort)

Thanks all - this was the info I needed (i.e. huge PSUs getting inefficient under tiny loads). I'll stick with either the 750 80+ gold or maybe even a slightly smaller PSU.

Thanks!

[xxx WreckinBallRaj xxx]

Having a PSU that is over what you need simply means it won't operate to its full potential. It is not wasting electricity but is wasting the extra money you spent on it.

[Monitus]

Bluten, on 09 August 2012 - 01:40 AM, said:

Having a PSU that is over what you need simply means it won't operate to its full potential. It is not wasting electricity but is wasting the extra money you spent on it.

It is also wasting energy (=money) due to poor efficiency PSU's have at low load levels. While it might not be much, it's still something. Here's a good article on the subject. http://www.anandtech.com/show/2624/1

[burn x]

Use this handy PSU calculator to give you a good idea what PSU you should be getting:

http://extreme.outer...culatorlite.jsp

[aphidgod]

A power supply's rating is its maximum output. It won't necessarily draw that much power at all times. Ideally you want a supply that's rated about 20% higher than your actual power draw. If in doubt, err on the larger side for improved efficiency. (Running a supply near capacity generates heat, which is inefficient.)

[Lightdragon]

im running an i5 3750k processor and a 7870 graphics card and the 750 watter i have in my case is way bigger than i need so.... 650 watt should be all you need for a single card setup sli... then you can get bigger

Monsoon, on 08 August 2012 - 10:22 AM, said:

Well in response to your thread title, yes there is such a thing, since your wall plug is limited to 15amps, which is about 1725 watts at 115 volts.

Now the most I've recalled seeing is 1200 watts, but keep in mind anything else your plug might have installed, like speakers, lamps etc. Also keep in mind if that wall mount is sharing it's power with any other mounts throughout that room/floor.



In regards to your expanded question, just how much do you plan to have in your computer? I suppose the biggest concern will be your Video Card and if your planning to have more than one installed. If you're only going to have one Video Card, one HDD and one SSD, chances are you won't have enough peripherals to even justify the 750w PSU. The 750w would probably be more than enough to cover even a second graphic card, depending on it's energy needs.

lol... my computer room is wired up all in 20 amps just because the 2 pc's my roommate built would constantly pop the breaker (both had over a kilowatt power supply)

[nksharp]

I have a silverstone 1200w

[Protoculture]

Shahadet, on 07 August 2012 - 07:43 PM, said:

So - as I'm collecting parts for my new gaming rig (as sales pique my fancy), I'm wondering if there is such a thing as getting a PSU that is TOO big for your setup?

I'm trying to set up my 1st time rig so that I can reuse some parts in future builds - such as the case and PSU.

My current incarnation has a 750 W, 80+ gold PSU from Corsair. But due to a sale, I can grab a Seasonic 80+ Platinum, 1000 W rig for just $55 more.

BUT - this initial PSU purchase will only really be powering a regular (un-overclocked) CPU, a high end GPU (probably 7950, 7970, or 670), an SSD drive, a 1TB HDD, and some fans and a CPU cooler fan.

Would it be bad for the system and/or the PSU to have so little load put upon it? Or would it be ok?

Thanks!
-AC

Without even reading your post and based solely on the title: No. Yes it might be overkill and you might waste some but you'd rather have more than you need than less believe me.

[Monitus]

Protoculture, on 09 August 2012 - 01:16 PM, said:

Without even reading your post and based solely on the title: No. Yes it might be overkill and you might waste some but you'd rather have more than you need than less believe me.

A little bit more won't hurt, but a lot more will just cost you more to buy and the power supply will never run at optimal efficiency. The picture I have linked shows the power usage of the current top end graphics cards in a rig with a Intel i7 2600K quad core. Even with the most outrageous dual graphics cards you barely get over 500 W load.

Total power usage of the PC with RED = playing BF3, BLUE = Idle on desktop.

(Source: http://muropaketti.c...x-690-2-x-gk104)

Don't waste your money for something you don't need and doesn't give you a single bit of added stability, efficiency or performance (fps etc..). Always buy a power supply that is enough, but not a overkill and is of good quality from a reputable brand.