Computers dont use as much electricity as some may claim

So today I wanted to figure out what the absolute maximum amount of electricity I could get my computer in my signature to use. According to the following site, each of my GTX 275s have a max TDP of 219W.

http://www.hwcompare.com/13381/geforce-gtx-275-vs-geforce-gtx-660/

However, GPUBoss.com says that cards have a total electrical consumption of about 40% above the TDP, so about 305W each. Then we have to consider my cards are overclocked as well. Then of course we have the CPU, which is also overclocked significantly, my three hard drives, six fans, PCI card, yada, yada, yada. Well theoretically, I should be pulling over 600W for the GPUs alone. So with everything, I should max out my 750W PSU, right?

Well, I wanted to find out. So I ran Prime95 to max out my CPU, and I ran Heaven Benchmark at the same time to max out my GPUs. I opened the resource monitor and Precision to make sure my CPU and GPUs were maxed. Then I used a KILL A WATT to measure the electrical consumption. The results?

With everything redlined, all the fans maxed, and everything overclcoked, the highest I saw the KILL A WATT read in the 60-second test was 505W. On average, it pinged around 450 - 470W, and when you take into consideration the inefficiency of the PSU (maybe 80% efficient), that means the computer components were actually using under 430W the entire time, and the GPUs likely never used more than 175W each at any given time. So where do they come up with this 305W per card for stock speeds crap? I dont think the cards even hit the official TDP of 219W. If they did, that would have meant the cards used 438W alone, leaving about 10W for the rest of the computer, which is just silly. So where do they come up with these numbers...? The only power consumption estimator I have found to match my real-world test is the following:

http://extreme.outervision.com/psucalculatorlite.jsp

Which also puts the electrical consumption of the GPUs way below the official TDP rating.

This is actually well known in these here parts.

Note, your PSU is 80+ BRONZE level. At the loads you are pulling you are around 85% efficient. So that peak value is around 429W actual use.

But yeah, I run a 290x Lightning and a 4.4Ghz 4930K on a 560W PSU with zero issues. I ran a GTX 690 and a 3570K @ 4.5Ghz on the same PSU which flips people's lids sometimes. People woefully overbuy PSU wattage in a lot of cases.

As far as your particular questions. I have no idea on that series of GPU how they are saying 305W each. There are no power limits on those cards, like modern ones, but that may have been with added voltage and an overclock? No idea.

Anyway, good to see on paper such things...

I'm betting the 305w was to include system wattage not just the card?

Janus67 said:

I'm betting the 305w was to include system wattage not just the card?

Click to expand...

This. It's always the intention to mark it as "you need this much power from your psu for the whole system for this".

I think that even accounts for the 80plus system.

Look at this link:

http://gpuboss.com/gpus/GeForce-GTX-760-vs-GeForce-GTX-660

It says the TDP of the GTX 660 is 170W. Then it says the "load power consumption" is 336W. This is the value I am talking about, and I have no idea where they are getting it, but I think it is false. The GTX 275s use more power than the GTX 660s, and according to this site the 660s would use nearly 700W for two.

that's full system load

Higher wattage/high efficiency PSUs are good idea if price is still reasonable as they are usually running at lower temps and fan is quiet. There is no way to make PSU quiet when it's 80+ bronze and is constantly running at 50%+ load ( or you have some magical series ).
Actually most that counts is what parts are in this PSU, not total wattage on the label. On the other hand you can't expect that 90% Platinum PSU will be cheap so sometimes it's better to get higher wattage 80+ bronze unit in lower price.
I have 1200W PCP&P that I got quite cheap and I'm using it in rigs that barely pass 450W but fan is not spinning for about 95% time.

TDP in computer parts is usually specified as max possible and it rarely hits value described by manufacturer.
Like Intel's 2 and 4 core CPUs have often the same TDP. I think that TDP is counted as max for worst batch as manufacturers won't tell you what voltage has CPU/GPU. In some series it's +/- 0.1V difference between the same products. In almost the same way you see graphics card voltage in software but when you measure it with multimeter then values are totally different. There you can have even 20W difference.

agreed, most systems never even go past 500w cept crossfire setups... err cough cough AMD FX systems jk

but for me a 4.9ghz 2500k and a 6950 overvolted and oc'd passed 6970 speeds barely pulled 400w from the wall on a bronze psu havent tested with my 280x yet but it has a very small overclock on it.

think a majority of systems could be handled fine by a quality 500w psu and i agree that most people would be surprised to see their actual power consumption.