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How to choose the perfect power supply for your gaming PC

A non-modular power supply unit for PC
(Image credit: Future)

The power supply is the beating heart of your gaming PC, the part that circulates the vital life-blood of power around your expensive processor, motherboard, and graphics card. The power supply can dictate the limits of your ambitions when it comes to potential PC upgrades, so it's always worth keeping one eye on the future when it comes to picking your next power supply.

Tech tested

Two of the best power supply units for PC gaming from Corsair and Seasonic

(Image credit: Corsair, Seasonic)

Best Power Supply for PC gaming: We've tested the best PSUs around to find the perfect choice for you. 

You have to determine first how many Watts your system, or prospective system consumes, and on top of that, you have to leave enough headroom for future upgrades. Moreover, you should keep in mind that the sweet efficiency spot is usually around 40-50% of the PSU's max-rated capacity. That and the closest a given power supply is to its max load output, the lowest the efficiency. 

So, if your system needs 500W at full load, it's not wise to get a 550W PSU but, at least, a 650W one. That said, most of us won't highly stress our systems all-around the clock unless you somehow have the time to constantly play games. Gaming can be seriously taxing on your PSU since they will generally fully load your graphics card, which is likely the most thirsty part of your setup.

To get an idea of what your system, or dream upgrade, will look like in terms of power draw you can easily enter all the particulars into a handy PSU calculator. We like to use the OuterVision Power Supply Calculator, but there are others available.

The most accurate way to determine your system's power needs is to use a kill-a-watt device and take some readings under full load, that's useful if you want to replace the existing PSU. Note that this procedure will only give you an indicative reading since it doesn't take into account your PSU's efficiency.

The most energy-demanding parts in today's systems are the GPUs with the CPUs following. Unfortunately, the manufacturers do not provide clear information on the actual GPU power consumption, and to make matters worse, you also have to consider possible power spikes that can reboot the system if the PSU isn't strong enough to handle them. 

On top of that, Intel and AMD's official TDP values for their CPUs are not even close to the actual power consumption numbers since they refer to normal and not boost clocks. Under increased frequencies, CPUs draw much more Watts than the official TDP from the PSU, and things get even worse, of course, if you decide to overclock. 

Even at default settings, some high-end CPUs can ask for 300W or more power. Yes, we're looking at you Mr. Core i9 11900K. If you combine this with a high-end GPU's power consumption, you will quickly figure that you need an 850W or even stronger PSU for a high-end gaming system. 

An ATX and SFX power supply side-by-side

(Image credit: Future)

The PSU's dimensions play a role in your next system build. You cannot use a standard ATX12V power supply in a mini-ITX chassis which requires an SFX PSU, for example. Thankfully, the prevalent desktop PSU form factors are restricted to the following

  • ATX12V (PS/2) [reference dimensions: 150mm (W) x 86mm (H) x 140mm (D)]
  • SFX12V 80mm fan [reference dimensions: 100mm (W) x 63.5mm (H) x 125mm (D)]
  • SFX12V Reduced Depth 80mm fan [reference dimensions: 125mm (W) x 63.5mm (H) x 100mm (D)]
  • SFX-L [reference dimensions: 125mm (W) x 63.5mm (H) x 130mm (D)]

The SFX-L is not an official ATX spec format, since it was introduced by Silverstone in 2014 and several other brands subsequently adopted it. It has longer depth than SFX to allow for a stronger platform. 

You've probably heard of Titanium, Platinum, Gold, and other metal ratings in PSUs. These indicate the PSU's efficiency, in other words, how much power the PSU draws from the socket to deliver power to your system. The more efficient the power supply, the better for the environment since it minimizes your carbon footprint. On top of that, you also save money on electricity in the long run. 

Currently, the two efficiency certification agencies use almost the same ratings, which you will find below: 

  • Diamond (Cybenetics)
  • Titanium 
  • Platinum
  • Gold
  • Silver
  • Bronze
  • White (80 PLUS)

Corsair AX1600i power supply opened up

(Image credit: Corsair)

Another significant decision you have to make before you invest in a new PSU is what type of cables do you go for; modular or not? Usually, the higher-end power supplies, which cost more, come with fully modular cables. You will generally only find fixed cables in the budget categories, and somewhere between the middle, you will discover semi-modular PSUs. Many of those also belong to the budget or mid-tier categories. 

If you can deal with fixed cables and need a PSU for a mainstream system, there is no need to pay more for a fully modular unit. But if you're aiming to use the bare minimum cabling, without a huge number of wires floating around your system, then a full or semi-modular setup is the way to go.

More and more people are starting to realise what an impact the PSU has on a system's overall noise output. As weird as it might sound, your power supply can play a significant role in the noise of your PC under load. 

The higher the efficiency, the lower the thermal load, so the PSU's fan doesn't have to spin at high speeds. This means that your best bet for a silent PSU is to buy one with the highest possible efficiency rating. Still, this doesn't mean you will select a dead quiet power supply, so it is good to read some reviews before continuing with the purchase. 

We've noted our own tested noise ratings in our best power supply guide to give you an idea of how the top PSUs sound. Cybenetics offers PSU noise certifications, so with a quick look in the corresponding database, you will find the PSU that meets your acoustic demands. 

The Cybenetics noise ratings are listed below:

  • A++ (<15 dBA)
  • A+ (15 to 20 dBA)
  • A (20 to 25 dBA)
  • (25 to 30 dBA)
  • Standard ++ (30 to 35 dBA)
  • Standard + (35 to 40 dBA)
  • Standard (40 to 45 dBA)

That's all you really need to know about choosing the right power supply as a PC gamer, but if you want to really dig into how a PSU works then we've got some words for you. That's the deep electrical stuff, but wattage, efficiency, cabling, and noise levels are the most important things to think when you're actually looking to buy yourself a new power supply.