Calculators VS Kill-A-Watt --REAL Power Consumption

[SirRob]

Question: When I upgrade, do I really need to get another 650+ watt PSU to compensate for inaccurate manufacturing specifications?

I have used many calculators to give me an idea of how much power my computer is using. They all state that my system uses 500 to 650 watts (or they recommend PSU's that will supply that much power).

When I plugged my computer into my Kill-A-Watt to see how much the PSU was drawing from the outlet, it NEVER exceeded 200 watts under load from before it posted through some stress testing! I ran Prime95 on each core and transferred data from a DVD-RW to a HD at the same time. I assume that if I were ripping from all three DVD-RW drives, running prime 95 on each CPU core, and transferring files between all 5 hard drives...etc, I could get it over 200 watts, but probably not by too much.

Knowing that the PSU is not 100% efficient, that tells me that even with a large number of components (but low end video card), my system is pulling well under 200 watts from the PSU. Am I missing something here? I have gone through two 550+ watt PSU's on various builds of this computer over the past 5 years. I use a UPS that does not condition the line. I understand that PSU manufacturers are notorious for overstating power ratings. One of the PSU's that failed was cheap, and the other one was a decent Fortron.

My current system is an Athlon 3800 X2 that has been overclocked at times, but is not currently. I will probably be upgrading to a decent Intel quad core soon. Except for the motherboard and RAM, everything else will stay the same.

Again: Do I really need to get another 650+ watt PSU? Am I missing something here?

 

[MarcVenice]

What videocard do you have? I doubt it's highend, and then the answer would be a simple no. A antec earthwatts 430w will run a qaudcore rig with a mainstream videocard ( single pci-e 6pin connector ) hell, the 380w is prolly powerfull enough as well.

 

[SirRob]

Thanks for the response!

The video card is a Radeon 1300 Pro.


Specs:
Athlon 3800 X2
MSI K8N Neo4
2 Gb RAM
Radeon 1300 Pro
(5) 7200rpm hard drives
8 USB devices
(3) DVD+/-RW drives
(1) 120mm fan
(3) 92mm fans
(2) PCI cards

 

[jdjbuffalo]

I don't know about you only needing 200 watts for everything. That does seem a little too low. But I doubt you are using 500 - 600 watts either.

Your setup is similar to mine (see my sig) but your current motherboard and processor are a few generations behind. If you keep the same type of setup and don't plan on expanding (e.g. no high powered graphics cards (GTX280), SLI setup or adding even more hard drives or PCI cards then a 500 - 550 watt power supply should be plenty. Make sure it's one that has the 80+% rating on it. As you may or maynot be aware you never get 100% of the power the power supply is rated for. You need to take the amount you'll need and add 20% that is the level of power supply you need.

Here is a great website that will help you calculate the estimated power draw: http://extreme.outervision.com/psucalculatorlite.jsp

I used the calculator on the website with the specs you provided and it came back with 350Watt Power Supply recommended. Obviously for the newer system you are looking at you'll want something closer to 500watts. One thing to keep in mind is if you plan on overclocking you will likely need something closer to 600 - 700 watts.

 

[MarcVenice]

jdjbuffalo, you have to read up on PSU efficiency, you don't have to add 20% to it, it's completely unrelated. A PSU could have 50% efficiency, and still be able to put out 500w, thing is, it will be drawing 1000w from the wall, and 500w will be lost in heat. Ouch. But no need to add 20% to your PSU.

Anyways, antec earthwatts 380/430w is plenty of power, or a lower powered seasonic s12 II 330-380w. Make sure it's QAULITY though, I can't vouch for crap units like huntkeys ...

 

[SirRob]

I just found out that APFC can fool Kill-A-Watts into giving abnormally low readings (some times giving better than 100% efficiency). That is probably what is happening in my case.

I am a believer in getting quality PSU's that may be rated lower instead of units that claim great specs but fail.

 

[JEDIYoda]

Kill A Watt`s are not reliable accross the board

 

[jdjbuffalo]

Originally posted by: MarcVenice
jdjbuffalo, you have to read up on PSU efficiency, you don't have to add 20% to it, it's completely unrelated. A PSU could have 50% efficiency, and still be able to put out 500w, thing is, it will be drawing 1000w from the wall, and 500w will be lost in heat. Ouch. But no need to add 20% to your PSU.

Anyways, antec earthwatts 380/430w is plenty of power, or a lower powered seasonic s12 II 330-380w. Make sure it's QAULITY though, I can't vouch for crap units like huntkeys ...

Thank you for correcting me. I had heard this misinformation several times before and never heard anything to the contrary.

For other people who want information about power supplies and the myths surround them check out this link: http://www.pcpower.com/technology/myths/

 

[magreen]

A quality 350-400W psu will be perfect for your needs, OP. No need for 500W and up.

One big reason a cheap unit is a bad idea is they lie about their ratings. Go read the reviews of cheap units on jonnyguru.com. These companies will get a cheap oem to manufacture them a 400W unit, for example, and then they'll slap a label on it saying it's a 600W unit. And it will run somewhere between lousy and ok at loads up to 400W. But run it near its rated capacity and it'll shut down, blow up, or worse yet, keep operating while sending ridiculous power spikes to your components, destroying them and itself in the process.

 

[dangman4ever]

Just an FYI, Paul Johnson of HardOCP made this reply to the OP's question (Most of it confirming what has been said here so far):
http://hardforum.com/showpost....1033326881&postcount=5

 

[SirRob]

You are correct. I have also been reading up at http://www.jonnyguru.com

From what I have read, it seems like a 500 watt power supply from: Antec, Corsair, PC P&C, Etasis, Silverstone, or BFG would do the job. That list came from the forums at jonnyguru (http://www.jonnyguru.com/forums/showthread.php?t=4985). I am keeping the upgrade to a quad core in mind. I have been using 550 to 650 watt power supplies for about 8 years now and it is hard mentally to go under 500 watts when so many have failed on me. I understand the quality of the PSU makes all of the difference in the world, but I do not think that I could ever go back to a 350 watt PSU powering 5 hard drives, 3 optical drives, and a quad core CPU. I do not want to be using it at capacity, but maybe up to 65% of maximum load.

Am I on the right path or am I still overshooting what I really need?

 

[magreen]

LOL...from what you said, you probably weren't running a 650W psu before now either... just one with a sticker that said 650W

Yeah, it's a fine idea to not run it so near its capacity, if you're so inclined to spend the $$ to get a higher wattage unit and not sacrifice on quality. That way it stays cool and quiet and the fan doesn't have to run at full speed.

Edit: COOL, my 666th post. I should get a special title just for while I'm at 666... like Satanic Member or something like that.

 

[bob4432]

here is what i found w/ my handy kill-a-watt -
http://forums.anandtech.com/me...id=27&threadid=2140807

i still need to upgrade it since i swapped psus again on system 7 and moved up to 1920x1200 lcd, so should pull more than 315W....

 

[frostedflakes]

Originally posted by: SirRob
I just found out that APFC can fool Kill-A-Watts into giving abnormally low readings (some times giving better than 100% efficiency). That is probably what is happening in my case.

I am a believer in getting quality PSU's that may be rated lower instead of units that claim great specs but fail.

I've never heard of that, but I'll have to look into it.

200w load sounds about right for your system, though, I doubt it's giving low readings. CPU is probably 50w or so load, and drives roughly 10w each. Then add the rest of the components and PSU losses. You can find online measurements of DC power consumption for CPUs and video cards that is helpful for calculating power usage. Xbit Labs has a really awesome setup for measuring DC power draw for their video cards.

 

[jonnyGURU]

Originally posted by: jdjbuffalo

For other people who want information about power supplies and the myths surround them check out this link: http://www.pcpower.com/technology/myths/

No.

That's where you go to find out about what "myths" need to be busted because they contradict PC Power's marketing.

 

[jonnyGURU]

Originally posted by: frostedflakes

Originally posted by: SirRob
I just found out that APFC can fool Kill-A-Watts into giving abnormally low readings (some times giving better than 100% efficiency). That is probably what is happening in my case.

I am a believer in getting quality PSU's that may be rated lower instead of units that claim great specs but fail.

I've never heard of that, but I'll have to look into it.

http://img.photobucket.com/alb...e_c_t_r_e/100_2710.jpg

215W AC from the wall according to the Kill-A-Watt. 219W DC load. Impossible.

The Kill-A-Watt is about 75W off in this picture.

That's why Paul @ HardOCP (the one who took that picture) now uses a more reliable Brand meter.

 

[bob4432]

Originally posted by: jonnyGURU

Originally posted by: frostedflakes

Originally posted by: SirRob
I just found out that APFC can fool Kill-A-Watts into giving abnormally low readings (some times giving better than 100% efficiency). That is probably what is happening in my case.

I am a believer in getting quality PSU's that may be rated lower instead of units that claim great specs but fail.

I've never heard of that, but I'll have to look into it.

http://img.photobucket.com/alb...e_c_t_r_e/100_2710.jpg

215W AC from the wall according to the Kill-A-Watt. 219W DC load. Impossible.

The Kill-A-Watt is about 75W off in this picture.

That's why Paul @ HardOCP (the one who took that picture) now uses a more reliable Brand meter.

wow, what do the brand meters run? or a reliable meter - nothing fancy, basically kill-a-watt functionality but accurate....

 

[SirRob]

There are some power supplies that have a digital readout that displays actual wattage. Any idea if those are accurate or just a gimmick?

 

[dangman4ever]

Originally posted by: bob4432
wow, what do the brand meters run? or a reliable meter - nothing fancy, basically kill-a-watt functionality but accurate....

Roughly $150 for the basic Brand Meter.

@ SirRob
Just a gimmick

 

[Concillian]

.

 

[jonnyGURU]

Originally posted by: SirRob
There are some power supplies that have a digital readout that displays actual wattage. Any idea if those are accurate or just a gimmick?

It's not "actual wattage". They're measuring at the wall like a Kill-A-Watt. Then they assume an efficiency (but not at a curve, so it's going to be less accurate depending on load) and then display the result of the calaculation.

Totally marketing.

 

[SirRob]

Thanks for the replies. So, I guess that I will just go back to doing educated guesses on how much my system will likely pull from the PSU and get a good PSU that can handle that load with room to spare.