How to know how much wattage?

[Scottagecheeze]

So I am putting together a build and I was wondering if there are any tips for figuring out how much wattage I will need?

Thanks

[UberFefa]

www.pcpartpicker.com

Make a build, it will tell you what it thinks. Then add like 30%.

eg. 300W system == 300*1.3 = 390W

If you plan on SLI/CrossFire, do the same thing, except add the second card.

[Dragon_Cannon]

Once you know what the total wattage is add some head room so that you can add other things into your computer later or if you keep the power supply for a long time it will start to not be able to provide the total wattage as it gets older.

[Guest]

http://extreme.outervision.com/psucalculator.jsp semi reliable :) most systems with a single high power GPU only use a max of about 600. Two GPU's and a bit of serious overclocking and I'd look into 7-850. Three way SLI/Crossfire then you're up into 1.2kw territory

[crispy345]

Use a PSU calculator, and remember to take the ratings with a grain of salt.

[killerx525]

In reality for my setup, 2 6950s plus a OCed 1090T only has peak draw of 527W for which i have a 750W power supply. So Windspeed's statement is pretty accurate.

[Dave :)]

I don't really trust PSU calculators, they seem very hit and miss. Sometimes they're very accurate, other times, not so much. Nevertheless they are still useful at times. Also, you can run most latest gen cards in SLI / Crossfire with a decent 650W PSU no problem, power consumption is forever decreasing with these cards and CPUs, so really, in the next few years, wattage will become alot lower for everyday users.

[Draex]

Plan for the life of the system when picking the PSU, any planned system upgrades such as SLI or Crossfire. Except 5-10% (Depending on the quality of the PSU) loss of capacity per year, regardless of how often the machine is on (Electrolytic Capacitor's have a finite lifespan regardless of how much actual usage they receive) Don't exceed 80% of the maximum output of the PSU if you can avoid it.