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How To Choose A Power Supply

Conceptualizing and putting together your dream PC is no straightforward task, but fortunately getting a few basics right puts you in good stead for the rest of the build. The best place to start is the power supply unit, and there’s no better way to choose a PSU than by focusing on the features covered in our guide.

Unlike other components, the power supply is not something you want to skimp on especially if you’ve spent an arm and a leg on a top of the line GPU. Power is performance. Let’s dive in.

The Importance Of Wattage

Pc Power Supply

If there’s one overarching rule when it comes to choosing the right power supply, it’s ensuring a PSU meets the wattage requirements of your graphics card, processor, and other hardware.

To break it down, every component in a computer requires a certain amount of watts from the power supply to function correctly. Under-power a machine and it at best struggles, and worse might not even start up. GPUs and CPU are generally the most power hungry components and therefore go a long way towards dictating how much energy is required.

Fortunately, when it comes to graphics cards and processors, manufacturers often provide the ideal amount of power supply wattage as an indicator for what to look for, either in thermal design power (TDP) or maximum power consumption. However, the value is only useful when considered within the context of a computer as a whole. Merely buying a PSU with enough power for your graphics card or processor will lead to an underpowered system.

How To Choose A Power Supply

In that sense, it’s worth making a tally of all the components in a computer and establishing a baseline wattage. You’d be excused for thinking that buying a 350 watt PSU for a machine requiring a total of say 345 watts is perfect. However, in reality, a PSU runs at maximum efficiency when the wattage draw is about 50% to 80% of its total output. Power supplies hate too much heat, and the best way to raise the temperature is by gobbling up all its power.

We would, therefore, recommend not pushing the PSU to 100% usage under any circumstance. Once you’ve tallied your wattage needs, aim for a power supply with a wattage output twice as high as what’s required. Not only will the power supply function better, but it also allows some leeway for future upgrades, overclocking, and expansion such as a better GPU.

The 80PLUS Rating System

Choosing A Power Supply

In this age of looming climate disaster and rising energy costs, you can save quite a bit of money by paying a little more for a power supply with a better efficiency rating than a lower priced competitor. The 80PLUS certification system grades PSUs based on efficiency.

Though the certification is voluntary, it indicates how well a power supply converts power from your standard wall socket to the lower voltage required by internal components. In essence, it comes down to how much energy is wasted as it is converted, i.e., how much heat it produces.

How To Pick A Power Supply

The certification is only available for PSUs that waste 20% or less of their power, hence the 80PLUS certification name. Most power supply units are stamped with a rating measured according to a sliding scale of familiar precious metals.

The classification runs from 80PLUS, through bronze, silver, gold, to platinum and titanium. In general, gold is the ideal middle ground for home users. The platinum and titanium units are usually reserved for high capacity server farms where managing heat is imperative.

Understanding Rails

How To Choose Power Supply

If you’ve been on the hunt for a PSU, you’ll more than likely have come across ‘+12V rails’ or a variant of some description. Other than having a seemingly confusing name, this feature determines how many rails feed power to different components in a computer.

A rail is a printed circuit board pathway through which the unit draws power. A PSU with a single rail has – you guessed it – one rail, while multi-rail systems distribute the power among multiple rails. Both setups have their benefits.

Single rail power supplies feed the full power of a unit from one rail to all the parts connected to it, ensuring every component is sourced with enough juice to work correctly. However, this does put the hardware at risk in the event of a power surge or malfunction as a big old spark of current can be blasted into every last nook and cranny of a PC frying it to oblivion.

On the other hand, a multi-rail unit is ideal for power surges as it will close off the power supply thanks to an inbuilt overcurrent and short current protection system in each rail. Conversely, multi-rail units don’t allow the even distribution of power across each rail. Instead, each one is assigned a maximum capacity and cannot breach this wattage threshold.

The feature isn’t in itself an issue if you ensure power hungry components like the GPU are fed power from an equally high powered rail. Manufacturers do an excellent job on jotting down power distribution among rails on the PSU casing or in user manuals.

Pin Connectors

How To Tell What Psu You Have

When choosing a power supply unit, you’ll want to ensure the model in question offers the correct connector type for your graphics card and other components.

Power supply units generally come with one of three connectors. The first is a 6-pin cable (75W), the second an 8-pin cable (150W), and finally the third a 6+2-pin, connected to either a 6 or 8-pin input thanks to two additional, detachable pins.

In general, graphics cards need a combination of either a 6 or 8-pin or even one of each. Research before purchasing is a must to avoid any issues.

Next up, we need to consider what connectors the motherboard needs to power the processor. Motherboards typically have one of four connectors; 24-pin, 20-pin, 8-pin, and 4-pin.

As with graphics cards, it’s all about ensuring the power supply provides the right connector. Most modern motherboards, especially boards targeted at gaming setups utilize 20 or 24-pin power.


Choose A Power Supply

An increasingly popular feature for PSUs is modularity, whereby connector cables can be attached to and removed from the back of the unit depending on the power needs of the PC’s components.

The main benefit is that modularity limits the number of unused, errant cables (or even cables that are too long or too short) clogging up precious space in the case, which simplifies cable management and by extension air flow. The PC runs cooler, therefore, prolonging lifespan and performance.

A small price premium is associated with modularity, but in our eyes, it is well worth the investment.


To summarize, check your wattage needs, get an efficient PSU to save power and money, and ensure you’ve got the right cabling and connectors to suit your build.

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