How Much Power Does Your Graphics Card Need?

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Calculating Power Supply Performance

Ideally, you’re not going to get close to the absolute limit of the power supply under constant load; the optimal range lies between 65% and 85% load. If load goes over 85%, the temperature regulation fan will run at full speed and you have to live with the louder noise. The next table shows the areas where brand name power supplies are at ease; those who aim for this region won’t have problems with the increased current flow at start-up from having multiple hard drives.

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Ideal Range--Power Supply Performance Class65% Load85% Load
300195255
350228298
400260340
450293383
500325425
550358468
600390510
650423553
700455595
750488638
850453723

Checklist:

1. Identify the graphics card and take note of the actual power consumption (in watts) under full load.

2. Identify the power consumption of the remaining components and add it.

3. Ideally, the area from 65% to 85% constant load determines the power supply class.

4. Maximum current level on the 12 V line is calculated and compared to the performance data from the power supply.

Formula: current (amps) = power (watts) / voltage (volts)

5. Check the required power connectors for the graphics card, and choose a matching power supply or allow for adapters.

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129 Comments Comment from the forums
  • Inktfish
    Could you please add the Radeon 4830? :)
    Reply
  • sepuko
    Took the words right out of my mouth.
    Reply
  • since Core i7 920 has TDP = 130W, how can it consume 85W only?
    Reply
  • 1.21 Jigawatts !!!
    Reply
  • nukemaster
    This article was due. No more you need an 800 watt psu for the 4870 , core2 quad ad 1 hard drive anymore :p

    Guest11since Core i7 920 has TDP = 130W, how can it consume 85W only?The TDP is more of a design thing. Almost all of Intels initial Core2 line had a TDP of 65 watts yet many took much less power. Intel gives a worst case of that type number and does not measure every cpu.

    AMD does the same thing. They listed almost all the initial Athlon 64's at 89 watts yet many did not take that or give off that amount.

    zxv9511.21 Jigawatts !!!You act like you would need a small fusion reactor or maybe a bolt of lightning to get that?
    Reply
  • neiroatopelcc
    So my system actually has a too big power supply to be effective?
    I'm running a 3,4ghz c2d with 5x500gb sata drives, a dvdrw and a 4870 on a p35 board.
    According to the article that's not going to draw the ~400W needed to get within effective range of my corsair 620 ....
    Reply
  • cynewulf
    There's a mistake in the power under load for the 3870X2. It shows the same as the idle consumption. If only that were true! :D
    Reply
  • Inneandar
    The TDP (thermal design power) is meant to be a guideline for the cooling solution, not the power consumption. To qualify for a cpu with a TDP of 120W, a cooler must be able to dissipate 120W. Practically, of course, this means it is an upper bound to (sensible) power consumption.

    also small note: Is it just me or is it strange to see the 260 SLI consume more than the 280 SLI. maybe in need of a beefier test scene...
    Reply
  • zodiacfml
    nice collection of data. i hope many learn from this and avoid recommending too powerful supplies.
    Reply
  • roofus
    better off with too much power supply than not enough. at least if you over-spec the power supply you leave some breathing room for any additional components.
    Reply