How many watts do you actually need?

Small guide to power requirements

| Source: OC3D Author: James Riley

Introduction

A lot of the time over on the forums, we see people list their systems with far larger power supplies than they'll ever actually need. The majority of single graphics card systems we see will rarely ever even require over 400 watts of power, despite a lot of graphics card manufacturers claiming you need more. Even an Intel 4670k with an Nvidia 780 Ti will run perfectly fine on a decent quality 450 watt power supply.

Today, we're showing you just how much power a decent high end system will consume, which may just put your mind at ease when planning your next build.

Specifications

Intel 4670K

Asus Maximus VI Gene

Asus ROG Front Base

Asus ROG Front Base Corsair Vengeance Pro 16GB 2400MHz

Corsair H100i

Asus GTX 780 Ti DirectCU II

240GB Corsair Neutron SSD

1TB Western Digital Green

Corsair RM450

Conclusion

As we can see in the video our system runs completely normally even on a small power supply such as the Corsair RM450. Of course, we'd always recommend a high quality unit regardless of which system you were running, and the price differences between a high quality 450w unit and a low quality 750w+ unit is pretty negligible. With a lot of people under the delusion that they need to spend so much extra money on a larger power supply, with the money they could save, they could put that towards upgrading other parts of the system. This could actually end up meaning a choice between a GTX 770 with a high wattage power supply, or getting by with a lower watt unit and being able to afford a GTX 780 Ti or an R9 290X.

A lot of the high quality power supplies these days have a silent operation mode when the system is requiring less than 20% of its maximum output. This is actually a reason why some people, even when they know their system won't draw much power, still opt for a higher wattage power supply in order to benefit from the silent fan operation. However, as we can see in the video, during idle periods, our system only requires around 90w of power which is still well within the limits of the idle fan mode of the RM450.

Now, once we've gone into more intensive programs such as a game, our system still only pulls between 350w and 400w, so it still has a fair amount of headroom before fully maxing out our RM450. Of course, there are many other decent power units you can choose, and some of the lower wattage units are completely fan-less too. As long as the PSU you're using is from a quality brand such as Corsair, you shouldn't have any problems.

When we stressed the processor on its own, we only saw our system pulling around 175w from the wall. This shows that even if you're using your system for mainly CPU intensive tasks such as photoshop or rendering, the PSU isn't going to be struggling much at all.

We have also tested various other systems for maximum power consumption. One of our rigs with a 3960X overclocked to 4.6GHz, with an AMD 280X only pulled a maximum of 434w from the wall, and numerous other lower end systems which only pulled around the 200-300w mark.

Recently, hardware has been getting more and more power efficient and so in the future, we expect results such as this to be possible on even lower wattage power supplies. Having said that, obviously if you plan on upgrading to an SLI or Crossfire set up in the future, it's pointless buying a 450w power supply and then changing it a couple of months later. This does prove itself as a very good demonstration of just how much power your system is likely to need. You may want to go for something slightly bigger in order to get a little more headroom so your power supply isn't running close to full capacity all the time, but this still may make you wonder just how much your own system requires.

So our final thought is if it means spending the same amount of money on a higher quality lower wattage unit then do it. Don't fall in to the trap of thinking a £60 800w power supply is going to be better for your rig than a £60 high quality 450 watter.

We'd love to hear your thoughts and opinions over on the OC3D Forums.

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