Build Advice Should you buy a more efficient power supply?

Extremely helpful thank you. Axi860 it is!

 

Some of your assumptions are off a single case fan is 3-4w, 12v@~0.3A, you will probably have more than one, including the fan on your CPU cooler, a motherboard and RAM consumption does not come for free etc. would be about 30-40w there on a reasonably featured board, less on a uATX setup. Though I guess you could argue you wouldn't hit TDPs in some cases, in other case TDPs aren't max power.

Intel TDP used to be based on typical usage and not the maximum the processor could pull in worst case scenario which was higher than TDP, don't know if that is still the case.

A quick look an they still define it as below which would imply it is still not a max.

Just looking at this site it would seem most gamers over clock so you can throw these TDPs out the window anyway

 

Great work. Very interesting indeed. Also, makes me feel better about having just bought a 450W SFX PSU for my rig (it is Gold Rated)

 

Makes me feel slightly happier about having a 1kw gold psu in my server at home that often is only pulling about 200w.

 

I'm with Parge, my 450W Gold rated PSU may not be as bad when it comes to energy consumption/cost etc as I worried it was

 

Good article Gareth.

The whole power argument has long annoyed me tbh. People go around spouting so called figures yet don't understand the actual costs involved, which usually turn out to be pennies rather than pounds.

 

Wouldn't a more valid comparison be between two PSUs of equivalent power but different efficiency?

For example, the £59 Corsair TX550M vs the £85 be quiet! BN198 Straight Power E9

Both have roughly the same power capabilities, but the Corsair is 85% efficient and the be quiet! is 93.2%, on paper. That's a much bigger gap than the two PSUs you compare, but with half the price difference.

Nice work, anyway, it made a good read.

 

Well I went to a 850 when 400 would have been enough for 2 reasons, size and noise. the model I got doesn't turn on fan under 50% load and it was one of the few PSUs that fit in my case.

TBH: Mostly got a large PSU so no matter what I do in the future I do not need to buy a new one.

 

It is a good write up Gareth. What I think is equally as interesting is how people calculate their loads prior to purchasing a PSU.

For example, if I were using my rig for benching/mining/folding 24/7 I would want a PSU which was as efficient as possible at the load level. It wouldn't bother me what the percentage load on the PSU was, just the efficiency at said load.

But I'm not that guy - I game a bit, casually. I still consider myself an enthusiast in the sense that I have a self-built reasonably priced ITX PC capable of HD gaming, but I'm definitely not hardcore.

I have an in-line power meter with the extension powering my sig rig, monitor & speakers plugged in. The exact contents of my rig which can draw power from the socket are as follows:

• Dell U2311H
• Creative T6060 5.1 Speakers
• Logitech G500
• Corsair K70
• Bitfenix Recon
• Corsair SP120 x 1
• Corsair AF140 x 1
• 2 x 1TB 7200rpm HDD
• 1 x SSD
• EVGA GTX770 SC
• Asrock Z77E-ITX
• 16GB Corsair Vengeance (2 x 8GB)
• Corsair H55 (wearing the SP120 above)
• i5 2500K (usually at 4.2 but happy up to 5GHz)

These are all plugged in to a Corsair CX500M - not the greatest PSU in history by any means, but it cost me £40 new with 3 years warranty, and it's more than suitable for my needs.

Now here's the thing - as I said above, I don't bench, fold or mine. I play games at max settings for a few hours a day on average. I have never managed to get my rig to pull more than 330W from the wall socket when gaming.

Case in point, when I run the Metro: Last Light benchmark at the settings detailed in this thread I get an average of 55fps for a total draw of 321W, although in reality it varies between 200 - 310W. For the whole rig, screen and speakers, playing one of the most graphically intensive games there is at basically max settings at 1080p.

If I turn my speakers (at a sensible volume) and monitor off I lose around 45W from that total bringing me down to 276W from the wall. Time for fun facts:

• The PSU fan is spinning at ~800rpm at this load (inaudible to all intents and purposes)
• The current-gen CX500M is around 87% efficient at 50% load, based on a couple of reviews I've seen
• I'm pulling 276W from the wall to supply 240W to my rig, playing a maxed out graphically demanding game
• The same workload using an SF-1000F-14MP would pull around 262W to produce the same amount of power

The bottom line for me was that whilst I could have spent more money for extra warranty and slight efficiency savings, the reality is that it would have been money wasted based on my usage patterns. When my warranty expires in 3 years I could buy another and still have change from what an AX760 would have cost me. I have also concluded that for a single card gaming rig, anything over 500W is likely to be overkill. I'm sure that's the general consensus anyway, but I do see an awful lot of 700-1000W PSUs in signatures here and elsewhere which are completely wasted based upon the other components listed. Not that I'm questioning people's choices at all, but the less knowledgeable system builder might well believe the hype that more is better.

Relevant article.

TL;DR I was jealous of Gareth's wall of text so I wrote one too.

 

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<3 UNICODE

 

I agree with that - the only reason I have a 1kw psu in my server is because I went down to 650 on my main rig which left me with a psu spare. My server is mostly cobbled together out of old bits so it's the nature of the beast. 650 on my main rig is probably still overkill - but i saw it on the marketplace here for what I thought was a bargain price, as is the driving force behind most of my purchases. I rarely ever buy anything new, and I buy things if I see them for a good price, kind of dictates my upgrades and the frequency of them

 

Oh fo' sho' - if you get a deal on a big PSU then it's a no-brainer!

 

Okay, fair enough!

 

Great read Gareth!

 

Interesting read, good stuff. Unfortunately I, like many tend to overspec the PSU in my builds to "leave some headroom" for future potentially power-hungry upgrades, multiple graphics cards or even to last the next couple of complete system upgrades.

At least that was my thinking when I bought my PSU (in sig) nearly 5 years ago - at the time I had a single 5770 and a C2D not C2Q. I think I may have misjudged things slightly.