How to Choose A Power Supply

We’ll give you the rundown on how to choose the right power supply.

How to Choose A Power Supply
One of the most difficult components for first-time builders to choose is their power supply. Power supplies won’t improve your framerate and they aren’t really a big part of your system’s aesthetics. However, there is no component more central to your system’s long-term health than your power supply.

If you choose a low-quality power supply, you run the risk of damaging your components.

On the other hand, if you don’t understand how much power you need in order to efficiently power your system, you could end up allocating more of your budget towards your power supply than is necessary.

In this article, we’re going to discuss seven different factors that you should consider before choosing a power supply. Understanding these seven points will help you pick the right power supply for your budget and needs.

Watch: What to Look for in A Power Supply

If you prefer the video format of this guide, you can watch it below, or on our YouTube channel.

1. Form-Factor

Power supplies come in a few different standard sizes. The majority of system builders will use a standard-ATX power supply.

However, if you’re looking to build a mini system, you may need to use a small form-factor PSU.

ATX vs SFX-L vs SFX Size Comparison

The PSU form-factor you need will be determined by your case. So, make sure you check the spec sheet of the case you want to use and see what PSU form-factors it supports.

If it’s a mini-ITX case, it may not fit an ATX PSU. Instead, it may only support an SFX or SFX-L PSU.

2. Figuring Out the Correct Wattage for Your System

Before you choose a power supply, you need to first figure out how much power you will actually need from your power supply in order to run your computer

You can do this in a couple of ways:

  1. Find power draw benchmarks on the components in your system (mainly, your GPU and CPU) and add them together to give you a minimum wattage rating.
  2. Use OuterVision’s power supply calculator.

In my opinion, OuterVision’s power supply calculator is the much easier and less time-consuming method for determining how much power your system will actually need.


All you have to do is use the drop-down menus provided to enter in your components into the calculator and then hit the calculate button to see what the recommended PSU wattage is for your system. With the ‘Expert’ tab you can even account for overclocking on both your CPU and graphics card as well.

OuterVision’s calculator is probably the most accurate calculator out there. Other calculators end up suggesting wattage ratings that are much higher than you actually need. As a good rule of thumb, though, it’s not a bad idea to add some headroom onto the number that OuterVision gives you. So, if it tells you that you need a 450W power supply, going with a 500-550W unit isn’t a bad idea.

3. A High Wattage Rating Doesn’t Equal A Quality Unit

Just because a power supply is listed as a 600W unit (as an example) doesn’t mean it can deliver that amount of power over a long period of time.

A lot of no-name PSU manufacturers list their power supplies at wattage ratings that are much higher than what they can actually deliver over a given period of time. Some first-time PC builders make the mistake of thinking that just because a power supply has a high wattage rating, that means it is a good enough power supply for their needs.

And, because a lot of these low-quality power supplies come in at ridiculously low prices, some make the mistake of thinking they are getting a solid power supply for a great price. The reality, though, is that they are purchasing a very bad unit that has a misleading wattage rating.

So, it’s important to avoid no-name power supply manufacturers and just stick to well-known manufacturers. Here’s a quick list of manufacturers who are known for making quality power supplies:

  • EVGA
  • Corsair
  • Seasonic
  • Antec
  • Cooler Master
  • Silverstone
  • Thermaltake
  • be Quiet!

This, of course, is not an end-all list and it’s important to note that not every power supply from the manufacturers listed above are quality units. So, it’s essential that once you know how much wattage you need, that you do your due diligence in researching what quality units are available in your price range.

The best way to do that is to read expert reviews or check our curated list of quality power supplies in our PSU Buyer’s Guide.

4. The Importance of Expert Reviews on Power Supplies

Testing a power supply is a bit more involved of a process as compared to testing/benchmarking other components. Take a look at the testing methodologies from a site like Tom’s Hardware.

As you can see, a lot of extra equipment is used in their power supply tests. And, some of that equipment is fairly expensive.

And, because the process of testing power supplies is a bit more difficult than testing other components, there aren’t as many power supply reviews out there as there are reviews on other components.

Fortunately, there are a handful of reputable power supply reviewers out there. Here are a few of them:

Before you purchase a power supply, it’s a good idea to check and see if any of the above websites have done a review on it first.

5. Modularity

PSU Modularity

Modularity refers to whether or not you have control over the cables on your power supply.

Fully modular power supplies come with none of the cables pre-connected and, instead, allow you to connect only the cables you need.

Semi-modular power supplies come with the most important power cables pre-connected (24-pin motherboard power & CPU power) and allow you to connect the remaining cables you need.

Non-modular power supplies come with all cables preconnected, whether you want to use them or not. For most builders who have no need of multiple SATA power connections, or molex connections, this will leave a whole bunch of left-over cables that will end up connecting to nothing. This group of cables will take up space in your case and look ugly if they can be seen.

If possible, we recommend that you use a modular power supply in your build. However, modularity comes with a premium and if you’re working with a budget, you may not have the option to get a modular power supply.

Of course, there’s nothing inherently wrong with using a non-modular PSU. It will just make cable management a bit trickier and can hurt the aesthetics of your build.

Also Read: What is A Modular Power Supply? Modular vs Semi-Modular vs Non-Modular

6. Efficiency Ratings

One feature you’ll run into when choosing a power supply is its efficiency rating. The most common of these are the 80 PLUS certification program, which has been around since 2004.

However, Aris Mpitziopoulos—a popular power supply reviewer who has written reviews for Tom’s Hardware and TechPowerUP—has recently launched a new PSU certification program called Cybenetics.

To understand these rating systems, you first need to understand a little bit of how a computer power supply works.

Your computer’s components use DC (direct current) power. However, the power coming from the outlet that your computer is plugged into delivers AC (alternating current) power.

Your power supply is responsible for converting the AC power from the wall into the DC power that your components need to operate.

During this conversion, there is some loss of power to heat. So, 100% of the AC power drawn from the wall does not get converted into DC power. A decent power supply will convert at least 80% of the AC power it draws from the wall into DC power.

A really good power supply will convert 90% or more.

These rating programs basically tell you how efficient a power supply is at converting AC power into DC power. But, it goes a little deeper than that, as the rating systems judge a power supply’s efficiency when it is under specific loads.

80 Plus

In order to earn one of the 80 Plus badges, a power supply must maintain a specific level of efficiency when it is under 20%, 50%, and 100% load. (The newest 80 Plus rating, Titanium, considers a power supplies efficiency when it is under 10% load.)

Also Read: 80 PLUS Bronze vs Gold vs Platinum vs Titanium: Which PSU Rating do you Need?

Here’s a table that breaks down each of the different 80 Plus ratings and what efficiency level it needs to reach in order to qualify for that specific rating:

80 Plus Rating Levels 115v non-redundant
% of rated load 10% 20% 50% 100%
80 Plus 80% 80% 80%
80 Plus Bronze 82% 85% 82%
80 Plus Silver 85% 88% 85%
80 Plus Gold 87% 90% 87%
80 Plus Platinum 90% 92% 89%
80 Plus Titanium 90% 92% 94% 90%

It’s important to note that the 80 Plus rating system isn’t perfect and doesn’t necessarily indicate that a power supply is a quality unit. And, therefore, it shouldn’t be used as the main determining factor in the quality of a power supply.

However, it is true that power supplies that achieve the higher spectrum of 80 Plus ratings (Gold, Platinum, and Titanium) are generally well-built and quality units. But, just note that, if you are in the market for a power supply, it’s a good idea to consider the 80 Plus rating system of a unit in conjunction with in-depth reviews on that same unit.

Cybenetics PSU Certifications

Just like the 80 PLUS program, Cybenetics seeks to provide consumers with information on how efficient a particular power supply is. However, Cybenetics was started because of inefficiencies they felt existing in the 80 PLUS program.

The main difference between the 80 PLUS program and Cybenetics’s testing is that where the 80 PLUS program measures efficiency across four different load levels, Cybenetics tests units across thousands of load levels.

Cybenetics also offers a rating specifically for noise levels as well. So, if you’re looking for a quiet PSU, you can use their rating system to help you choose the right option.

Browsing through the Cybenetics’ PSU database will tell you how in-depth their program is. The program also offers a 15-page PDF report for each unit that contains all of the results from their tests.

The program is still young and is not widely adopted, but it’s only a matter of time before PSU companies start sharing their Cybenetics rating in their marketing materials—either alongside, or in place of, their 80 PLUS rating.

The bottom line is that, where the 80 PLUS rating system will overrate some units, the Cybenetics rating system won’t.

So, we before you choose a power supply for your build, we recommend checking Cybenetics database to see if they have tested the unit and, if so, what rating they have given it.

7. A Quick Note on Power Supply Aesthetics

For a large portion of people who build their own computers, aesthetics play an important role in the component selection process. However, power supplies are one component where aesthetics usually doesn’t play a large role.

Yes, there are RGB power supplies out there. And, there are power supplies that look better than others.

However, for me, the main thing I look for in a power supply in terms of aesthetics is mainly its cabling/sleeving.

You can spend a lot of time ensuring that your other components are color-coordinated and you can have the cleanest cable management around and you can show it all off inside of a case with a nice full-glass side panel.

However, if your power supplies cables look like this…

multi-colored cabling

…the multi-colored cabling is going to take away from the aesthetics of your build and your system won’t look as nice as if your power supply came with all black cabling like this…

black cabling

If you don’t care about aesthetics, obviously you don’t need to worry about the color of a unit’s cabling. And, if you are purchasing a modular unit, you can always swap the cabling out for custom sleeving, too.

However, if you are budget-oriented, but you still want to build a nice-looking build, just know that of the more affordable power supplies out there, there are some units that will have all-black cabling that won’t take away from your build.

So, while aesthetics aren’t a major thing to consider when buying a power supply—especially at the higher end of the market—the cabling, to me, is an important aspect that you might want to consider if you are looking to build a clean-looking system.

Choosing the Right Power Supply

While power supplies might not be the sexiest components in PC builds, they are one of the most important. In this post, we’ve given you five things to consider when choosing a power supply for your build.

If you take these five factors into consideration, you’ll have a much easier time choosing the right PSU for your needs.

Hey, I’m Brent. I’ve been building PCs and writing about building PCs for a long time. Through, I've helped thousands of people learn how to build their own computers. I’m an avid gamer and tech enthusiast, too. On YouTube, I build PCs, review laptops, components, and peripherals, and hold giveaways.

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