Some interesting power information

[Whisperfang]

My UPS allows me to hook it to my computer via USB and then feeds my computer wattage data about how much it's using.

Quick specs of comp:
Corsair 620HX
3GB DDR2 (2x1gb, 2x512mb)
Intel Q9450 @ stock
Nvidia GTX 280 @ stock
BenQ G2400WD 24" LCD

Idle, sitting at desktop: 205w being supplied by the UPS (keep in mind, my 24" LCD *is* plugged into the battery side of the UPS)
all 4 cores at 100%: ~260w
all 4 cores at 100% & video card at 100%: 470w

My video card sucks an extra 210w at full load. The neat thing is, this proves to me that most people do NOT need 500+ watt PSU's. There is nothing out there that can possibly stress all 4 cores + video card other than pure benchmarking software, or maybe some really high end rendering software or something like that. Bottom line is that my computer is already faster than probably 90% of the computers out there and it's only drawing 470w max. And that's coming from the UPS which means it takes into account the loss of efficiency from the PSU. So in reality my system is drawing about 385w (assuming ~82% efficiency) at full load and that's including a 24" LCD.

 

[Tigerbiten]

If you run Folding on your computer then you can easily run 100% load on both your CPU and Vid cards.
The one I'm on now, Dual 5450's and single 9800GTX+, pulls 400 watts from the wall, sans monitor, and thats under half the power draw of my top folding box, Quad 9800GX2's.

But I agree, most computer don't need +500 watt PSU's.

Luck ..............

 

[Whisperfang]

Addendum, i turned off my speakers and monitor and took a screenshot, with just the computer taking power, it uses 140w at idle.

 

[Zero82z]

So if your PC itself uses 140W at idle and with your speakers and monitor uses 260W, that means you have an overhead of ~120W for those two components. That basically puts your PC's real wall draw at around 350W, which comes out to ~290W DC once power efficiency is factored in. So your PC really draws about 290W of power at maximum load. I bet that's quite a bit less than you originally assumed .

 

[JonGerow]

The neat thing is, this proves to me that most people do NOT need 500+ watt PSU's. There is nothing out there that can possibly stress all 4 cores + video card other than pure benchmarking software, or maybe some really high end rendering software or something like that.

How much of this load is on the +12V rail? Seriously. If you had a 500W power supply with 75% of it's capability on the +12V rail and you actually loaded up the +12V rail to 400W, power supply fall down go boom.

And I've often measured higher numbers doing simpler things. For example: 600W from the wall just running Vantage on a pair of GTX 280's. No Fut or Prime or folding. Also only one HDD, water cooling, etc. Very basic build outside of the dual GPU's.

It is true that the whole 1000W, 1200W, 1600W craze has gotten out of hand. You only need a 1000W+ if you're running three way SLI. Even if you have 4+ drive RAID arrays. But devices like your UPS, Kill-A-Watt, etc. aren't very accurate unless you have a static load (almost impossible to do unless you're using a load tester) and even then they are often tricked into showing lower numbers by APFC circuitry. They can't measure transients loads either because the sample rate at which they measure is too slow.

That said, your 620W is a perfect fit for a single GTX 280. I'd dare say you could probably pull off two. I just wanted to make sure it was clear that you can't just assume that a < 550W PSU would be adequate just because your UPS says you're using only 470W. In fact, I bet if you put a 400W in your system, you'd lock up or reboot running the same tests, and your UPS would still say you were only pulling 470W from the wall under full load.

 

[Whisperfang]

After doing my testing, i've actually come to a conclusion that i may need to upgrade my UPS. It's only rated to deliver max of 540w and if a full load test is 470w, that's bumping too close for my comfort. I wasn't doing anything related to cdrom drives, sound, or super memory intensive. All that would take extra power. I would think that if i was able to completely max the system as best as i could, i'd be drawing close to 500w. My UPS software was already complaining about the 470w load (my UPS would only be able to supply that much current for 4 minutes).

 

[Whisperfang]

So if your PC itself uses 140W at idle and with your speakers and monitor uses 260W, that means you have an overhead of ~120W for those two components. That basically puts your PC's real wall draw at around 350W, which comes out to ~290W DC once power efficiency is factored in. So your PC really draws about 290W of power at maximum load. I bet that's quite a bit less than you originally assumed .

I recalculated everything, full load my computer itself would only use about 330w with most of that on the 12v rail. This means my PSU would be fully capable of supporting GTX 280 SLI. And it is an SLI certified PSU after all.

 

[Zero82z]

After doing my testing, i've actually come to a conclusion that i may need to upgrade my UPS. It's only rated to deliver max of 540w and if a full load test is 470w, that's bumping too close for my comfort. I wasn't doing anything related to cdrom drives, sound, or super memory intensive. All that would take extra power. I would think that if i was able to completely max the system as best as i could, i'd be drawing close to 500w. My UPS software was already complaining about the 470w load (my UPS would only be able to supply that much current for 4 minutes).

As long as you don't try to play Crysis while running off of battery power, I think you'd be fine with your current UPS (unless you want to play Crysis while running off battery power ).