What power supply (in WATTS) to get with my custom built computer?

Question

I'm building a customer PC. I know that I will need to get more then the standard 400 watts that come with the PC Tower. But how exactly do I find that out and figure exactly what I need???

I know I could just post my specs on here and someone will answer is for me... but I want to know for future computers, how do I know?

I have tried looking on video card and CPU specs to see if it lists some kind of energy requirements and I saw none.

Any help on this topic, I would really appreciate it.

Answer 1

Nowadays, the +12V rail or rails is MORE important than TOTAL wattage of power supply. This is because most of the power is now drawn from that rail. These are the loads on the +12V rail:
1. Processor/voltage regulator circuit= Processor could draw 5 to 10 amps depending on model. Core2 Duo usually draws up to 5.4 amps. The regulator circuit could draw a few more.
2. Graphics cards= Budget cards draw less than 3 amperes; mainstream cards, 3 to 6 amps and high end cards 9 amps or higher.
3. All fans and motors of FDD, HDD and DVD/CD

Here's my rough guide on +12V rating needed for cool and stable operation all day long:
1. Simple set up on integrated graphics or a budget video card = 15 amps
2. Gaming set up with a mainstream video card =20 amps or higher
3. Gaming set up with mainstream cards in SLI or a single high end graphics card = 30 amps or higher
4. Gaming set up with high end cards in SLI = 40 amps or higher

Answer 2

Either one will do, the 9600 GT really only requires a 500 watt power supply since it isn't a high end card. The 650 watt PSU is sufficient to run 2 9600 GT's in SLi. The number of hard drives is not a problem. Also, as a suggestion: if this is a gaming-only computer you might want to cut down the RAM to 4 gigabytes and spend the extra cash on getting a better graphics card, for example, a GTX 460 or a Radeon 5850. Games don't require more than 4 GB of RAM.

Answer 3

Don't use Ohm's Law :p

Video Card (sometimes chipset) manufacturer's say what they require for there systems. Even in crossfire or sli.

Most cheaper brands advertise there "MAX" theoretical output. If you notice the more expensive brands have way more amps per rated wattage.

In short, going off of wattage is like sizing up two pickup trucks based on there tires. It actually does work, to a point (i'm a car guy to), but it's not accurate.

I know about wattage and voltage. Ohm's law get's thrown out the window on pc's since power supply wattage's / amperage / efficiency's are so mixed up. Another example: 300hp 2.0L Honda vs. 300hp 7.4L Cummins diesel :p

Check the link for a semi-currnt PSU calculator.

Answer 4

If you are planning on having these items, 2 hard drives, optical drive, mid to high end video card, higher end processor(s) I would plan on at least a 550W power supply. Antec, and Enermax are the two brands of power supplies that I would recommend because I have never had issues with either brand. Look for ones that are certified 80% efficient or higher... that will mean less heat output and a lower overall energy bill.

Answer 5

Ok first off, some companies make a power supply that is "700w". They label it this way because it COULD hit 700w. Go with a well known brand (Thermaltake, Antec) and shoot for 550-650w, make sure it has a decent amperage on "the 12v rail". Anyone who sells good power supplies should know what that means.

Answer 6

Most hardware user reference guides will have the power consumption list. However, on a high-end gaming PC (such as mine), you may want to consider 800W to 1000+W power supplies. Personally, I have 2x750W PSU's (Combined 1500W) which is plenty. Hope this helps.

Answer 7

simple : amps x volts = watts

Example: 5 amps x 12 volts =60 watts