Forum Announcement

Welcome to the new CNET Forums! Please don't panic. You are not in the Twilight Zone, you are experiencing the new CNET forums platform! Please click here to read the details. Thanks!!

PC Hardware

General discussion

Calculating power Supply needed

by Ifrit24 / May 20, 2008 1:43 PM PDT

So I am planning on upgrading stuff in my computer but I don't know how to figure out if i need to upgrade my powersupply or not. how do i figure it out?
thanks
Ifrit

Post a reply
Discussion is locked
You are posting a reply to: Calculating power Supply needed
The posting of advertisements, profanity, or personal attacks is prohibited. Please refer to our CNET Forums policies for details. All submitted content is subject to our Terms of Use.
Track this discussion and email me when there are updates

If you're asking for technical help, please be sure to include all your system info, including operating system, model number, and any other specifics related to the problem. Also please exercise your best judgment when posting in the forums--revealing personal information such as your e-mail address, telephone number, and address is not recommended.

You are reporting the following post: Calculating power Supply needed
This post has been flagged and will be reviewed by our staff. Thank you for helping us maintain CNET's great community.
Sorry, there was a problem flagging this post. Please try again now or at a later time.
If you believe this post is offensive or violates the CNET Forums' Usage policies, you can report it below (this will not automatically remove the post). Once reported, our moderators will be notified and the post will be reviewed.
Collapse -
Widely documented.
by R. Proffitt Forum moderator / May 20, 2008 9:28 PM PDT

My short version.

20 Watts per drive.
100 Watts for the CPU
40 Watts for the mainboard.
40 Watts for the usual video card
100 Watts for the firebreathing video card.

Add it up and then double it so it lasts for years.
Bob

Collapse -
10,000 RPM hard drive?
by satish_997 / June 17, 2008 2:08 AM PDT
In reply to: Widely documented.

I assume this would use more than the average 5,400 or 7,200 RPM drive.

About how much more power would you say is used by Western Digital's 10,000 RPM Raptor?

Collapse -
go by the recommendation for your video card
by ramarc / May 20, 2008 11:48 PM PDT

if it's not a gaming video card, just get a 400w power supply.

Collapse -
Here is a site that I have found helpful
by CardsFan29 / May 21, 2008 12:22 PM PDT
Collapse -
Thanks for the web site
by Dango517 / May 23, 2008 7:11 PM PDT

I've looked this over several times and this is generally difficult to do. The best I'd determined was that if you purchased a $3,000.00 or less PC then go 500 watts, over $3000.00 then 1000 watts. Seams I was right. My calculations from this site recommended 447 watts for my system.

http://extreme.outervision.com/PSUEngine

I would suggest the originator of this post look for a PS that is at least 80% efficient or better. Also the heavier the PS the better. Yep, heavier by weight. This means the PS has more windings and is of better quality. Also, if your running a SLI video card you will need an SLI Power Supply.

Collapse -
Respectfully disagree....it would be easy to overload a 500
by VAPCMD / May 24, 2008 2:08 AM PDT

watt PSU in a PC (sans monitor) under $3,000. Just a couple of the high-end...not highest-end, video cards; 2-4 HDDs; 2 CD-DVDs; 4GBs RAM; and dual or quad core CPU and you'd be too close or over the 500 watt PSU threshold. If you bump the PSU to 700 watts and lower the threshold to $1,000 or $1,500 that might be closer assuming it was a quality 700 watt PSU.

VAPCMD

Collapse -
hmmmmm
by Dango517 / May 24, 2008 5:13 AM PDT

With up grades I have a $1,200.00 PC. 500 watts would run it well with a little wiggle room. The three thousand dollar mark was for high end multiple (two or more, maybe four) hard drives, more then likely RAID. Two or more Video cards, 4-8 GB RAM, quad processor and water cooling. Certainly this type of PC would need more power. Most PCs are pretty "run of the will" till you pass the 3 grand mark. A system builder might create a $2,000.00 PC that would need a 1000 watt PS but they'd need to be a really shroud shopper. There out there on the net somewhere but the audience here is more mainstream. My comments reflect the audience we deal with here, not the PC gamer elite.

Collapse -
Audience aside, you can spend way under $3,000 and still
by VAPCMD / May 24, 2008 7:21 AM PDT
In reply to: hmmmmm

need a PSU greater than 500 WATT PSU. Said another way...we could probably all agree if you set the dollar threshold much lower.

VAPCMD

Collapse -
(NT) I'm done
by Dango517 / May 24, 2008 10:41 AM PDT
Collapse -
well now
by dturner0528 / October 15, 2012 3:21 AM PDT

well i would hope that if one buys a $3000 computer that it would come WITH a psu, or that the existing psu's wattage would be sufficient enough for the owner to tell the necessary wattage by simply looking at the sticker on it.

Collapse -
A little late. Four years.
by R. Proffitt Forum moderator / October 15, 2012 3:25 AM PDT
In reply to: well now

Thanks for this but I'm finding that not only must I consider Watts but the Amperes on the "rails."

Some power supplies have plenty of Watts but fall short on the Amperes needed for these graphic cards because the +12V rail is not one but many.
Bob

Collapse -
Adding to what others have said....
by VAPCMD / May 21, 2008 12:48 PM PDT

having a higher wattage power supply unit (PSU) is better than a PSU with no reserve or headroom over your minimum requirement. Assuming PSUs with the same efficiency, a 500W PSU uses no more electricity than a 300W PSU in the same system. But in real life, PSUs vary in efficiency....80+ is one of the benchmarks and it's one of the factors to consider when buying a PSU you leave running 24-7.

For example, you might buy an inexpensive 400W PSU for $20 or a higher quality, higher efficiency 400W PSU for $40, $50 or $60 and depending on use, make up the cost difference in efficiency in 4-6 months. Low upfront cost is often not the bargain it appears to be...especially when it comes to reliably powering your system.

If you want to read more about PSUs...do some reading over at http://www.jonnyguru.com/

Good Luck on your search

VAPCMD

Collapse -
Calculating power Supply needed
by rezaulice / October 17, 2012 1:27 PM PDT

20 Watts per drive.
100 Watts for the CPU
40 Watts for the mainboard.
40 Watts for the usual video card
100 Watts for the firebreathing video card.

Popular Forums
icon
Computer Help 47,885 discussions
icon
Computer Newbies 10,322 discussions
icon
iPhones, iPods, & iPads 3,188 discussions
icon
Security 30,333 discussions
icon
TVs & Home Theaters 20,177 discussions
icon
HDTV Picture Setting 1,932 discussions
icon
Phones 15,713 discussions
icon
Windows 7 6,210 discussions
icon
Networking & Wireless 14,510 discussions

Tech Tip

Tired of your tricky Wi-Fi password?

Stop trying to memorize a complicated sequence of numbers and letters. Learn how to change the default password.