Do you over estimate your PSU need?

bigdogchris

Fully [H]
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Feb 19, 2008
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Says I only need 375 watts and I thought I would need a 700 watt.

http://www.extreme.outervision.com/PSUEngine

I've read before that companies (nvidia/ati and others), incredibly overestimate power requirements because they take into consideration that people may have 4 optical drives, 6 HDD's, a bunch of lights and like a dozen cooling fans :rolleyes:

I think the truth is, if you just have the bare minimal, just mean business, that you don't need as much power as you think. But I think everyone can agree this doesn't mean it's OK to start buying cheap power supplies.

Said a core 2 e8500, SLI GTX280's and 4 sticks of DDR is only 550 watts ... (not my system). That's not bad considering most people say 800-1000 is needed.
 
That is probbaly one of the most accurate calculators around actually. And yes, IMO, a lot of people do overestimate their power needs.
 
It has been a while since I checked that calculator, but it seems reasonably accurate.

582W for this rig:

Q6700 @3.5GHz
HD4870 790/1100
2Gb DDR2
2 SATA HDDs
2 36Gb Raptors
1 DVD RW
Antec 900's fans
USB stuff

10% capacitor aging.
 
I always do. It saves me upgrades later on...

My server needs 580W and I got a 750W.
 
They increase the power specs because PSU's age and decrease their max output over time.
The nearer it is to its max output and/or the hotter it is the faster it will wear.
So if you push a PSU near its max it will wear faster, further reducing its max output, therefore making it work even harder, wearing it faster..... pop!
Theres nothing good about a PSU being pushed too hard and going bang.
Gfx card manufacturers get an RMA if the card gets killed.

I'm using a good 630W on an 8800GT.
I dont recommend anything less than a good 500W for the GT but do advise to get higher.
 
I do lol. Thought I needed 650+ but I only need about 502 watts 100% load.

E6550 @ 3.0ghz 1.3625vcore
2x2gb DDR2 800
ATi HD 4850 785/1100
7 case fans
usb stuff
4 hard drives
2 dvd drives.
 
Always do. As others have stated it saves on upgrades later and allows me a little more headroom to feel safe. I could have made due with an 850watt on the system in my sig but I went 1000watts anyways for future use. No telling what video cards will be doing in 2 years or so. ;)

-V
 
I really should be.. but my 500w basiq works pretty well. And who says popping PSUs aren't fun??
 
i have a 750w psu that my backups says im using about 350w under full load but that also includeds all of my stuff to get out to the net.. i plan to get another 4850 so i know i have plenty of room.

 
I just used the calculator for system I know the measured power of. I was surprised it came out within five watts of the measured value.

Yes, I oversize my power supplies for all the reasons given above. Often power supply specs are not quite right. It will run cooler and last longer. Capacitor aging should be accounted for, and the calculator allows for this. And future upgrades may need more power.
 
I do by about 1.5 to 2x.

Like LOCO said, it saves you from worrying about the PSU when the next upgrade comes around and it also keeps the PSU in the lower RPM part of it's fan speed curve.

You don't want to over estimate TOO much because most PSU's are inefficient < 20%, although the difference is only about 2-5% and only accounts for about $2 a year in your electric bill.
 
I always do, with PSU prices being what they are there's really no reason to not overestimate.
 
There's no such thing as "too much". I just recently bought a bunch of equipment that will cap out at roughly 300W of power at peak perfomance. We are talking full bore 100% cpu and video card usage.

I bought a 650W PSU. Why? Cause like JonG above said PSU's can be overstated and inefficent. It may say 650W but you might be lucky to get 500W out of it. It's better to go 30-50% more on it just in case something goes "wrong" or you plan on upgrading to hungrier components in the future.

700W is tons of power for god almost everything you can find unless you are stacking 10 hard drives deep and 2 Nvidia 280s or something ridiculous.
 
Just make this simple for your self. Buy a Ultra X3 1600W with lifetime warranty and be done with it.
 
Q6600 OC'd to 3600 @ 1.4v
HD4870 CrossFire (to mirror a 4870x2 purchase)
2x2GB DDR2
4 SATA drives
1 SATA optical
5x Scythe 120mm fans

I get recommended PSU wattage of... 590w.

Does that mean my Corsair 620HX is no go for 4870x2 considering the whole 20% efficiency?
 
BigDogChris: I always overestimate PSU requirements. An HX620 should have no problem driving a 4870x2 in your rig. I'll be upgrading to a 4870x2, as well. I'm sticking with my HX620 PSU.

E-mail Corsair for a 6+2 power cable. You'll need one and it's free! :)
 
Does that mean my Corsair 620HX is no go for 4870x2 considering the whole 20% efficiency?

He stated 20% inefficiency which translates to 80% efficiency.
It was a bit confusing but he made a valid point that there is a range of power output levels when the PSU operates more efficiently.
The further outside that range, the lower the efficiency.

LocoLaptop mentioned being done with it and using a 1600W PSU.
It will work fine - but for below 500W system (actual use not rated), it is going to lose efficiency for sure.
 
Woah

E6420 @ 3.7Ghz 1.5v
8800GT 512
3 HDs Sata
2 sticks of DDR2
2 DVD-RW
2 120mm fans
3 92mm fans

434w

Guess that if I plan on upgrading to a Q9450 and HD4870 i'm gonna need a new PSU.. :/
 
I'll always overestimate my psu by at less 33%. Who wants to run their psu at near 100% load 24/7?
 
Says mine eats 333 watts and my PSU has 650. Sounds good to me since most PSUs are not meant to be run at 100% usage for more than a split second and I do take my system up to close to 100% load often lol.
Also, never know what video card I will be getting next and how much juice it might eat! what If I suddenly decided I wanted a phenom quadcore overclocked and a 4870x2?
 
Good quality PSU's, like the ones often recommended at [H] are rated for CONTINUOUS power, not split second availability.
 
He stated 20% inefficiency which translates to 80% efficiency.
It was a bit confusing but he made a valid point that there is a range of power output levels when the PSU operates more efficiently.
The further outside that range, the lower the efficiency.

LocoLaptop mentioned being done with it and using a 1600W PSU.
It will work fine - but for below 500W system (actual use not rated), it is going to lose efficiency for sure.

Okay, good to know.

I wanted to run a 4870x2 but man, i am rather hesitant on getting another PSU just because this one cannot suffice, which is sad cuz the 620HX is a champ.

I think I will stick with the 4870x2 and the 620hx, hope for the best, heh. thanks =)
 
This calculator says I need a 750W PSU and I'm running mine on an enermax 620....

Makes me feel a little better about purchasing the 1200 watt I have on the way. Although it is running fine for now?

Well, my old system was 600 watt according to this calculator and I was running the same Liberty 620 watt. I guess I'm stressing the PSU every time I load up the system?
 
Good quality PSU's, like the ones often recommended at [H] are rated for CONTINUOUS power, not split second availability.

Then how come they don't do the torture test at 100%? Theoretically they should be able to handle it right (im sure a few could, but not many lol).
 
I'm getting 527 with my rig:

Q6600
2 sticks DDR 800
1 SATA 7200 hard drive
Nvidia 9800GTX
2 DVDRW
1 250mm fan
3 80mm fans
3 USB devices

I plan to add a sound card, TV tuner and a single ATI 4870x2. Calculating this with just a 4870 raises the estimate to 598. Maybe I'm mistaken to think my HX620 will handle a 4870x2?
 
Then how come they don't do the torture test at 100%? Theoretically they should be able to handle it right (im sure a few could, but not many lol).

Who's "they"? All the PSU torture tests i've seen done at Anandtech always go up to 100% and the ones that pass 100%, they then take them up to 110% of their rating.
 
Who's "they"? All the PSU torture tests i've seen done at Anandtech always go up to 100% and the ones that pass 100%, they then take them up to 110% of their rating.

He's referring to HardOCP. Taken from the recent HardOCP review of the FSP Everest 1010W PSU:
Torture Testing
The final component of our load testing involves our 8 hour torture test. This test is meant to simulate what gaming or hardware enthusiasts might encounter when they use their systems for extended periods of time under stressful conditions such as 3D gaming or long term stability testing and benchmarking. However though, we do not suggest using your power supply at 100% loads for extended periods of time and our torture test does reflect this. We load the PSU being tested to ~80% of its rated capacity for 8 hours at a temperature of 45c. This is outlined in our testing Methodology should you wish to have more information.
 
Well in that case, I don't know why HardOCP doesn't load to 100%. Don't get me wrong, I agree that it isn't a good idea to constantly run your PSU at 100% of it's capacity, BUT they good ones are rated for continuous power output. And while HardOCP may not test to 100%, Anandtech does, and even past 100% if the PSU can manage it.
 
Well in that case, I don't know why HardOCP doesn't load to 100%. Don't get me wrong, I agree that it isn't a good idea to constantly run your PSU at 100% of it's capacity, BUT they good ones are rated for continuous power output. And while HardOCP may not test to 100%, Anandtech does, and even past 100% if the PSU can manage it.

HardOCP does load the PSU to 100%, just not for the Torture testing. If you look at Test 4 of the Load Testing page of most of the [H] PSU reviews, you'll see that they do load the PSU to 100%.
 
yep i overestimate cause sometimes it still aint enough. the room is sometimes 80 right now without trying -- this crappy 400w huntkey from best buy popped running a measly celeron 356 with one sata and dvdrw...
 
Sitting at double the wattage I need according to that calculator, with my Corsair 620 HX. I thought I used a little more power than that, but it was the sort of ratio I was hoping for. *Plenty* of room for upgrades, and not even close to stressing it.
 
I think the biggest overestimate comes from people running SLI. You don't need a 800W PSU to run SLI.

But even though it says I only need 4-500 watts, I wouldn't feel comfortable with using less than my 700Watt.
 
Then how come they don't do the torture test at 100%? Theoretically they should be able to handle it right (im sure a few could, but not many lol).

Who's "they"? All the PSU torture tests i've seen done at Anandtech always go up to 100% and the ones that pass 100%, they then take them up to 110% of their rating.

He's referring to HardOCP. Taken from the recent HardOCP review of the FSP Everest 1010W PSU:

Well in that case, I don't know why HardOCP doesn't load to 100%. Don't get me wrong, I agree that it isn't a good idea to constantly run your PSU at 100% of it's capacity, BUT they good ones are rated for continuous power output. And while HardOCP may not test to 100%, Anandtech does, and even past 100% if the PSU can manage it.

This at the top of EVERY load test page in EVERY review:

http://www.hardocp.com/article.html?art=MTI4OSwsLGhlbnRodXNpYXN0

And at the top of the torture test page it tells you why. Every PSU is schedluled to run for an hour at 100% load.
 
There's no such thing as "too much". I just recently bought a bunch of equipment that will cap out at roughly 300W of power at peak perfomance. We are talking full bore 100% cpu and video card usage.

Power supplies over 1.5kW will exceed the rated 15A for an electrical outlet, so yes, there is such a thing as "too much."
 
I guess the best example of what happens when you buy a psu to *get by* will be apparent pretty quickly once the 4870X2 is released, I expect to see an influx of folks who are learning lessons the [H]ard way.
 
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