EggXpert

Okay this is kind of bugging me -

I'm finalizing my build and was just about to order everything up this morning.  I had used NewEgg's power supply calculator and selected an Antec Earthwatts PSU.   At the last minute I opted for a nicer video card and decided to recalculate my power needs only to find that they shot up around 100 watts! 

The problem is that NewEgg's calculator doesn't include HD 3870 graphics cards so I set it to "HD 2900 Series" figuring that it would be close enough.  I consulted a few other calculators online but they all gave me drastically different results so I figured I'd attempt to actually talk to someone about it.

Is there a calculator that you guys here rely upon with up-to-date component choices?  I just want to hurry up and put in my order but I don't want to overestimate my power needs and end up with some overkill PSU. 

I'll include the specs of the build for some information. 

Thanks for your time!
 

eXtreme Power Supply Calculator is one of the more popular ones.

EDIT: Keep your future upgrade goals in mind. I'm sure you don't want to shell out money for a replacement power supply when a new more powerful card comes out, or if you decide to CF two cards.

Yeah I tried using the eXtreme one but it gave me such a low rating I didn't think it was accurate.  Here are screenshots from both NewEgg and eXtreme:

Since NewEgg doesn't offer much room for specificity, it seems that it should be a little different from eXtreme's more specific calculator, but this is a 300w difference!

Well there ya go, 344watts it is, heh.

Just FYI, the Max draw for the 3870 is 105 watts.....the Max draw on the 2800XT is 215watts.

Also, the Intel Core 2 Duo processors wattage ranges greately.

344 Watts is more reasonable.

Splic:

For the record, I was planning on using a 430w until I saw NewEgg's estimate.

Let me guess the Thermaltake 430watt PSU, If so it would work, even though I'm not crazy about the efficiency (which will get important if you leave your pc on 24/7).  What's your maximum that you'd be willing to spend on a power supply alone?

Actually I was looking at the Antec Earthwatts EA430w (which was great because it had a hefty rebate).  The next step in that lineup is the 500w which is double the price (after rebates), but I'd also like to keep a low profile and save some energy, which it seems the Earthwatts is good at.

Worst case scenario - I get the 430w and end up overloading it - what happens?   

Splic:

Actually I was looking at the Antec Earthwatts EA430w (which was great because it had a hefty rebate).  The next step in that lineup is the 500w which is double the price (after rebates), but I'd also like to keep a low profile and save some energy, which it seems the Earthwatts is good at.

 

Worst case scenario - I get the 430w and end up overloading it - what happens?   

well, it will just turn off.  The Antec Earthwatts line has over power protection, so if you try to pull more power than the power supply can handle, it will just shut off.  

However, with your computer setup, you will definitely not be overloading that power supply.  Here's a quick power estimate, using the max power draw wattages for the components you listed:

CPU: 65watts

 GPU: 105 watts

optical drive: 25watts

hard drive: 10watts

motherboard: 50watts

 RAM, cooling, PCI cards, etc: 50watts

max power draw:  305watts, at max load.  

so, that Antec Earthwatts would work fine for you.   You'll have over 100watts of extra power, in case you decide to add, say, another couple DVD drives or hard drives. 

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lowboy:

Comp Wiz is a WIZ at recommending under powered PSUs. There are many more things to consider than adding those numbers up.

could you elaborate on what these "things" are?  If you add up the max rated power draw of all of the components, you get the total power that the computer can draw(in fact, components rarely actually hit their rated max power, even when running demanding applications).  There's really no way that another 200watts can just disappear. 

This type of calculation has been verified with real world testing.  For example, The Inquirer built a high-end gaming computer a little while ago, using two 8800GTX's in SLI and a high-end Intel-quadcore CPU(I can link the article if you'd like).  This system ran perfectly on a high quality 500watt power supply.  Also, they monitored the power that it was pulling, and the max power draw of the system never exceeded 430watts.  However, I've seen people on these forums recommend 1000watt power supplies for systems with similar components.  If we simply add up the max draw for the components on that system:

CPU: 130watts

GPU: 145watts each

motherboard: 50watts

hard drive: 10watts

fans, RAM, PCI cards, etc: 50watts

we get 530watts.  So, as you can see, actual consumption is usually considerably lower than the amount calculated by my method.  This is because it is really difficult to load components up to 100% load.  Some companies have released special test programs that are made to get the load as high as possible, so you can test your cooling.  But, most programs, even demanding video games, will not push power consumption up to the max rated levels.  Now, you wouldn't want to assume that this will be the case, and subtract watts from the max draw figures to try to get a lower wattage estimate, as some program might just come along and actually need all that power.  But, using the max draw figures will ensure that all of your components can draw their max rated power at the same time without a problem. 

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Well, here's my beef with it. Why would you get a PSU that can just barely handle the load? you'll be running it at 100% all of the time (if you game allot like me) and you will blow that PSU out way before its time. Why not go for 25-50% more than you need just so it will not only last longer, but you will still be able to use it if you upgrade any of your components later on.

Just makes more sense dude.

Peace

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I recommend the OCZ GameXStream OCZ700GXSSLI 700W ATX12V Power Supply

If you're going to spend money on new computer parts, you should atleast invest in a GOOD power supply.

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GmsCool:

Well, here's my beef with it. Why would you get a PSU that can just barely handle the load? you'll be running it at 100% all of the time (if you game allot like me) and you will blow that PSU out way before its time. Why not go for 25-50% more than you need just so it will not only last longer, but you will still be able to use it if you upgrade any of your components later on.

As I pointed out in the above post, your computer's components will rarely, if ever, actually hit their max rated wattage, and they probably won't all hit this max draw at the same time.  Just gaming will not push them up to this max draw and hold them there.  So, even if you were to find the exact rated wattage for all of your components and then get a power supply that matches that exactly(which is not something I ever recommend), even while gaming the system would not be sitting at 100% load constantly.  It might peak up near there for brief periods of time if you're running very demanding applications(like running CPU Burn-in while running 3Dmark vantage gpu test while defragging your hard drive and burning a CD), but during normal usage, you'll never reach the max draw wattage of your computer. 

And, if you look back at all my posts here, you'll see that I never recommend getting a power supply that exactly matches my max power draw estimate.  I always recommend getting something with somewhat more wattage.  What I have a problem with is when people recommend power supplies that have double the wattage required.  These power supplies tend to cost considerably more, and really will never be used fully.  The chance of someone upgrading their computer to the point that it draws double the original wattage is really low.  Most people just add a few hard drives and possibly another optical drive.  Looking at posts on here, people who would be doubling their power requirements, like upgrading to a high-end Intel CPU, and adding a couple very high-end graphics cards, realize that they'll need more power, and with a purchase of that size, the cost of a higher wattage power supply is fairly insignificant.  It just isn't financially viable for most people to buy a power supply that can handle any future upgrades that it would be possible for them to make.  If they think that they may get another graphics card and run SLI in the future, or any other upgrade they're planning on doing, I always incorporate that into my wattage calculations.
 

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specialist:

I recommend the OCZ GameXStream OCZ700GXSSLI 700W ATX12V Power Supply

If you're going to spend money on new computer parts, you should atleast invest in a GOOD power supply.

seeing as the max rated power draw of his computer is only 305watts, I think a better power supply to get is the OCZ GameXStream 600watt power supply, currently on sale for $45.  The GameXStream 700watt power supply that you linked costs $95.  Paying over double the cost just to get an extra 100watts(that you most certainly do not need in this case) is probably not a good idea.  Plus, testing of the OCZ 600watt power supply at Hardware Secrets showed that their 600watt power supply can actually put out 729watts of power without a problem. 

Of course, the Antec Earthwatts 430watt power supply is an even better deal.  It could even run the computer with another ATI 3870 graphics card in crossfire, but that would be getting a bit close to the max wattage of the power supply.  If you do think that you'll be running crossfire in the future(or putting in a GeForce 280 GTX), I'd recommend spending $15 more to get the OCZ GameXStream 600watt power supply, but otherwise, save a bit and get the Antec Earthwatts PSU.  As I said above, you'll have over 100watts power more than you'll need, so adding a couple hard drives or optical drives won't be a problem. 

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Sheesh..I can blow those figures out as even extreme PSU cal. shows 473 Watts when used correctly.

I agree with gmsCool: Why would you get a PSU that can just barely handle the load? you'll be running it at 100% all of the time (if you game allot like me) and you will blow that PSU out way before its time. Why not go for 25-50% more than you need just so it will not only last longer, but you will still be able to use it if you upgrade any of your components later on.

GOOD sound advice.

lowboy:

CompWiz quote:seeing as the max rated power draw of his computer is only 305watts,

Sheesh..I can blow those figures out as even extreme PSU cal. shows 473 Watts when used correctly.

I'm curious as to what you mean by "used correctly", as from the wattage that you got, it would seem that you used it incorrectly.  Yes, you can change some of the more obscure settings there and get a dramatically higher wattage than what is realistic, but that's not using it "correctly".  

lowboy:

I agree with gmsCool: Why would you get a PSU that can just barely handle the load? you'll be running it at 100% all of the time (if you game allot like me) and you will blow that PSU out way before its time. Why not go for 25-50% more than you need just so it will not only last longer, but you will still be able to use it if you upgrade any of your components later on.

As I said in response to gmsCool's response, I would never recommend a power supply that would be running at 100% capacity to handle a computer's max load, or be just barely able to handle the load.  In fact, the power supply that I recommended would have over 100watts more power than the computer needs, even if the computer was loaded up to full load. 

Also, a computer rarely ever hits its max rated load, even if you are gaming.  The only way to hit the max rated wattage on your computer, is to run special programs to completely load each component.  Like CPU Burn-in to load the CPU(one instance for each core), the ATI GPU-test program to load the GPU, some windows-based memory program to load the RAM, a defragmenter to load the hard drive, and burn a CD to load down the optical drive.  That's not something that just gaming will do. 

another power supply deal just came out that you may be interested in.  The OCZ StealthXStream 500watt power supply is currently on sale for $30 at newegg, with free shipping. Use the coupon code EMCAGCGBD to get the $30 price.  That's a high quality power supply with about 200watts of power more than your computer needs.  So, you could definitely upgrade to two ATI Radeon 3870's in SLI, or add a few of hard drives and optical drives, without stressing the power supply. 

The OCZ StealthXStream was recently reviewed at Hardware Secrets, with very positive results, if you'd like to read more about it.   

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Where Newegg's and the one linked to above ask for motherboard type, it has a choice of regular and high-end. What is the difference(for the purposes of the calculators)? Or What's the definition of each? I doesn't seem to make a signifcant difference in the calculation but I'd like to know anyway.

I just did the systyem I'm building (2.8GHZ dual core CPU, 2GB RAM, 1 HD 1, CD-ROM drive, 1 DVD writer, onboard video only, PCI ide controller) in the eXtreme  calculator and it says 188W. That can't be right can it? NewEggs says twice that. What's with the discrepency?

 eXtreme's doesn't have a selection for on-board video. I guess yo have to choose the model of the integrated GPU?

heat84:

Where Newegg's and the one linked to above ask for motherboard type, it has a choice of regular and high-end. What is the difference(for the purposes of the calculators)? Or What's the definition of each? I doesn't seem to make a signifcant difference in the calculation but I'd like to know anyway.

I just did the systyem I'm building (2.8GHZ dual core CPU, 2GB RAM, 1 HD 1, CD-ROM drive, 1 DVD writer, onboard video only, PCI ide controller) in the eXtreme  calculator and it says 188W. That can't be right can it? NewEggs says twice that. What's with the discrepency?

 eXtreme's doesn't have a selection for on-board video. I guess yo have to choose the model of the integrated GPU?

 Well, you've just listed out a few of the reasons why I don't like these wattage calculators.  Essentially, you're feeding information into a black box, and at the end, it comes up with a number.  You have no idea how accurate that number is, or what some of the more obscure settings(capacitor aging, motherboard type) actually do to the final wattage. 

It's really more accurate if you calculate the wattage yourself.  It's not hard to find wattages for most of the higher wattage components of your computer(like CPU's, GPU's), and other common components can just be added in(like hard drives: 10watts each, optical drives: 25watts each).  Then, put in 50watts for your motherboard and another 50watts to cover cooling, pci-cards, and RAM(only accounts for a few watts).  Usually that second 50watts is a little overkill, but it's better to be a little on the high side.  Also, the motherboard wattage is an estimate, I have yet to see an article measure motherboard power draw.  So, if the actual motherboard power draw is a little higher than 50watts, the second 50watts added in should cover for that. 

If you could list your components here, I can walk you through a max power draw estimate.  

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