How to Choose the Best PC Power Supply

Tech gadgets today are sprawled all over – both in our home and workplace. And our reliance on tech is at an all time high; as our lives become even more technology dependent by the day. In fact, any unplanned downtime with our devices would send most of us into a complete frenzy; especially when it comes to our computers! And that is why the power supply is one of the most important devices within our tech arsenal when it comes to computers. It’s thus critical to purchase a quality power supply, as the consequences of a cheap power supply can wreak havoc on both your computer system and files.

To find out which power supply is best for you, let’s go over three factors that you need to consider when looking to purchase your device:

  • Power Output
  • Efficiency
  • Modularity and Cables

Power Output

On average, your computer consumes approximately 275 watts of power at full load; depending on the type of computer system you have purchased or assembled. Thus, we will use this 275 watt figure in our example below when going over how to select the best power supply size by using two important variables.

Variable #1 – Headroom

The first variable is the headroom. If your computer consumes 275 watts of power, you don’t want to purchase a 300 watt power supply. A 300 watt power supply will overheat while its lifespan decreases, since it will constantly be running at approximately 90% load. Instead, you want to go with a 500 or 600 watt power supply, in order to ensure your power supply works properly when you need it the most.

Using a high rated power supply will not lead to greater power consumption, however. Rather, it gives the power supply greater headroom as your computer system advances (is upgraded). As a result, the power supply can still be used in the future and be protected under unpredictable circumstances, while remaining efficient in operation. Therefore, it’s important to remember that if your computer system draws 275 watts in consumption, then both a 300 watt and 600 watt power supply will both consume the same amount of power.

Variable #2 – Voltage Rails

A voltage rail refers to one single voltage provided by the power supply. Related to a computer, the voltage rails are the different voltages from the power supply that supply different components within a computer. More specifically, we are interested in the power given to each rail. As an example, the +12V rail has significant importance because this rail supplies power to a computer’s graphics card. Your graphics card is typically the most expensive component inside your computer, thus, you want to ensure that it remains protected with an adequate supply of power.

When selecting the +12V rails, we must consider two types: single and multi. A power supply with a single +12V rail will provide uninterrupted power to the device that it is backing up. The other type is a power supply with a multi rail, where each rail has a max power output limit. With a multi rail power supply, you must be careful over which components are plugged into each rail, otherwise you can overload and shutdown the power supply. For example, if you have a computer component that draws 50 amps, you must be sure that the rail providing the power is rated for at least 50 amps.

Multi rail versus single rail power supplies

Both the single and multi rail types are good power supplies – performance wise; yet, the single rail is the best option in most cases.


Higher efficiency rated power supplies are simply better quality builds. With power supplies, the 80 plus certification program is used to showcase efficient energy use. What this means is that a power supply that is 80 plus certified will have more than 80% energy efficiency at 20%, 50% and 100% rated load. These certified units will waste 20% or less electric energy as heat at the given rated load levels, and in turn lowering electricity usage. Thus, your monthly electric bill will be reduced, compared to using less efficient power supplies. Now that’s always a win!

The takeaway here is that the higher the efficiency rating, the better quality power supply you will be receiving. See the table below for the 80 plus efficiency detailed breakdown for reference.

Power supply 80 Plus Certification comparison chart

In reviewing the table, we can see that at 50% load, power supplies have the greatest efficiency. This circles back to why the headroom factor, which we discussed earlier, is so important. Having your power supply at approximately double the rating of your computer system requirements will keep your system less heated and will create less noise.

The 80 plus certification comes in six tiers:

  • 80 Plus
  • 80 Plus Bronze
  • 80 Plus Silver
  • 80 Plus Gold
  • 80 plus Platinum
  • 80 Plus Titanium

Note: for consumer level units, the 80 Plus Gold is typically the best choice.

With increased inefficiency, the outputted power decreases with more dissipated heat.

Power converter efficiency - input and output

Modularity and Cables

Not as important compared to power output and efficiency, yet, for some, modularity can be a deal breaker. When a power supply is described as modular, it simply means that some of the cables that run between the power supply and computer can be taken out when not in use.

The modulatory of a power supply is generally classified under three categories:

Non-modular power supply – the power cables for the motherboard, hard drive, and PCI Express are hard wired to the PSU.

Full modular power supply – you can remove and replace every single cable that is within the power supply.

Semi-modular power supply – this falls in-between the two options above. Typically, the motherboard power connector is hardwired; yet, the hard drive and PCI Express power cable can be removed and replaced.

The choice in modularity helps keep an organized and tidy work area, and allows you to use your own more descriptive or stylish colored or braided cables. However, it’s very important that you never mix modular power supply cables between brands or even models – as you are risking component damage.

There you have it!

First, find out how much power your computer system consumes, and then purchase a power supply rated twice your system power requirements. For example, if your system requirement is 300 watts, then purchase a power supply rated at 600 watts. As well, be sure the power supply is 80 plus certified. These certified units will be more expensive; however, they will have an extended life and will better protect your computer when you need it the most.

There you have it! Look through power supplies with ease the next time you’re shopping, and find one that is safe and reliable for your use.

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