Hi guys,

I'm upgrading my system and i am a bit confused about the psu power. My question is let's say that the maximum power consumption of the components at the full load is 300w. If the psu is 500w then does that 200w end up as a waste which is added to my bill as something I didn't use OR the components draw only the power they need in which case I pay only what I used for?

Any help appreciated.

The components draw only what they need.
But the power supply itself will consume some electricity. And, in general, the higher the wattage, the more it will consume so it usually makes sense not to buy a power supply that's too powerful. But this isn't always true because good power supplies consume less electricity than bad ones. If you want the exact figures, check good reviews made with reliable meters (like the ones on the main site).

To chose the right power rating then you need to look at what components you have. In general power supplies are massively overrated for the required load. This is very inefficient as power supply efficiency is best at moderate to high loads, not 20%. It also is costly too.

There are a few PSU calculators out there:
http://extreme.outervision.com/psucalculatorlite.jsp

What components are in your system? Maybe if you can list them here then a more accurate suggestion can be made.

Thanks for the hand guys.



GIGABYTE GA-Z68AP-D3 = 75w (just about)
Kingston Hyper X (2x4gb) = so small
i5 2500 = 95w
2*SEAGATE 3.5" 1TB Barracuda Sata 3.0 32MB Cache 7200Rpm = 20w
ZALMAN CNPS5X cpu fan = ?
Quadro 600 = 40w
2-3 fans = 8-10w
DVD writer = 30w

Well, I've already done some calculations and arrived at roughly 268w. Considering the fact that a psu meets a system's target power requirements most efficiently when running at 80% of its rated wattage, I added to this figure a bit more (268/0,8) and found 335w as the optimal wattage. So, I guess a psu with 450w should be OK for now. I said 450w because in the future I may install mid-level graphics card for games. At present integrated card should be OK.

So what do you think about this psu power?

I highly doubt that a Z68-mainboard will draw 75w. I doubt any board ever did, not even nForce 4 abominations. These new boards don't even have a northbridge anymore, it's just a passive southbridge and then a whole lot of chips that don't even get cooled with a heatsink. I'd calculate with 25w or so.

And the DVD writer only consumes power when it spins, i.e. when you burn stuff with it. Now unless you purposefully try to max your power load, it's unlikely you're gonna push the i5-2500 to 95w (which btw is more than it will actually use anyway) while also burning a DVD.

I think you're likely looking at under 200w real max power. I remember a couple of years ago I measured my then gaming PC (overclocked and overvolted Core 2 Duo and Radeon X1950XT) and it reached 260w at the wall plug, so maybe ~210w at the PSU.

The thing is, you're not having a whole lot of quality PSUs under 500w, so you're probably still best served choosing a good 450/500w model.

+1

Take a look at the 400-650W recommended PSUs. I think something like the Kingwin LZP-550 would be a good fit.

Even if I use the integrated graphics? Also did you take 80% efficiency thing into consideration when making suggestion?

The integrated graphics is not on the motherboard, it's in the CPU.

The two most demanding components are usually the GPU and the CPU (hard drives too, if you have lots of them). Since these combined only consume 95 W when burdened with almost unrealistic workloads, 450 W will easily suffice. Even with a dedicated GPU. Just pick a reliable PSU from a reliable brand.

What is your budget in this? If money is no object then the Seasonic X-400 or Kingwin STR-500 are both amazing. As suggested already, you won't find that quality in lower rated power supplies but they are very expensive. A Seasonic S12II-330 might be a more real world solution.

The power rating of the PSU never includes efficiency loss. The rating is the output power, not input power. Eg. If a system with an 80% efficiency PSU is drawing 150W from the wall (this is normal at load) then the components are only requiring 120W of this, the other 30W is waste heat.

Just a "me too" on going with a quality 450/500W PSU, and that those much lower in capacity tend not to be of the finest vintage.

If it helps provide a level of comfort, this is what I have connected to a Corsair HX520 (ie 520W) PSU: X58 motherboard, i7 980X, 12GB RAM, 3 x hard drives, 1 x SSD, DVD, AMD 7950 graphics, fans, all USB ports used. Idles (quietly ) at 130W at the wall.

Running a game like Skyrim with everything turned up is around 270W at the wall.

If I run Prime95 and Furmark together (an extreme workload well beyond normal use) hits 430W at the wall. So the actual system load is around 365W (85% efficiency).

See also http://www.silentpcreview.com/Recommended_PSUs

martin

I just read an HD 7750 review that had a i5-2500K and 82% PSU that pulled 121W AC while gaming. So, yeah. Don't need a lot of power these days.

As you say money is no object, want to build a good system that should last at least 6-7 years.

As for the 80% efficiency level, I think this relates to two different things. Ok I know there psus out there with different efficiency levels ranging from 70 to 90, but in my second post above, when saying 80% efficiency, I was merely referring to what I've read in the following pdf file in page 4, you may wish to take a look at it:

http://forum.corsair.com/forums/showthr ... post469981

PSU can be more efficient than 90% but that number is useless. The real efficiency of the PSU depends on the real load. You will not get its optimal efficiency.
So you'd have to determine what you effective load is going to be in order to know how much effciency you're going to get. This is tedious work and may not be worth doing since, as mentionned above, the best PSUs are all too powerful anyway.
If you want a full PSU and if you care more about efficiency than cost, the Kingwin/Superflower Platinum 550W seems the best all around.


Well, that's not completely wrong but it's wrong enough to make it misleading. Don't trust manufacturers or vendors.
The peak efficiency of the PSU I just mentionned for instance seems to be around 35% load, not 80%.

Much as I respect Corsair products (I use more than a few), this is written by marketing. The guys that want you to buy a bigger ie more expensive PSU. The PSU rating they manage to achieve by rounding everything up massively is laughable.

martin

If you want to see some REAL marketing bollocks about power supply ratings, what better than the otherwise worthy company Silvertone with their inane misguided rambling entitled "Why use a 1500W power supply?":
http://silverstonetek.com/techtalk_cont ... d=wh10_005

They're wrong.

Even if they were right, the reasoning would only apply if the typical load was full load...

says http://silverstonetek.com/techtalk_cont ... d=wh10_005 which clearly contradicts with the statement in corsair's psu guide pdf file (%80) .



I think you are right guys. I studied marketing at univesity but couldn't realize it was all about ripping people off, lol.

So the bottom line is that a 450w psu should be ok for the system I'll build. I just wonder if the power consumption of i5 2500, as stated in the intel's web site, could be more than 95w under heavy load or is this the maximum amount it would spend? what do you think guys?

Chip manufacturers state a "Max TDP" aka Maxiumum Total Design Power. It is the very worst case possible heat output of the CPU package for designers of heat sinks, cooling etc. Almost impossible to make an actual processor hit its Max TDP (without grossly overclocking).

If you browse Intel's specs online you'll see that several numbers repeat, such as 65W, 95W, rather than a precise number for each chip. Not unusual to find the same Max TDP for supposedly different speed processors. This is for the convenience of thermal designers - they can use one of the common Max TDP for a range of processor models.

martin

Thank you guys for taking your time to explain the things. Appreciated.