Can you use an SFX power supply (PSU) inside an ATX PC case?

What's unique about an SFX PSU?

If you're wondering how to fit an SFX PSU in an ATX case, you should know what makes this form factor unique. SFX PSUs are compressed versions of normal power supplies, or ATX PS/2s. An SFX PSU is smaller in size and made to fit into tiny cases. Otherwise, it's electrically the same. You won't have to worry about your components not getting enough power.

That said, there can be some differences that could matter depending on how you want to set up your build. The smaller size might open up some breathing room for components, but it can introduce some complications as you try to install it.

How to fit an SFX PSU in an ATX case

Here's where things get tricky to explain. How well a SFX PSU fits into an ATX PC case comes down to what the case recommends or supports. Generally it should fit, but you might need an adapter that lets it screw in as a normal PSU would. These aren't expensive or anything, but they can be a burden to get if you already have your build ready to go. Make sure to check whether your SFX PSU comes with one or not.

Some cases come with this support by default. You'll have to check what the case can handle. For the most part, if it's a big ATX case, versus an ITX one, you should be able to fit anything in there. PSUs don't get bigger than that. If it is indeed a smaller case, it should slot in without an adapter as that is what these types of PSUs are made for. One you have that though, it should perform just as well as any other PSU like the NZXT C650.

The SFX PSU cable problem

One sort of hidden feature with SFX PSUs is that they have shorter cable lengths. This is largely because in small form factor cases, you want everything to be clean and efficient. You don't want cable nests to stop airflow in an already tight situation. Of course, this is a problem in a big case where your components are spread out.

SFX PSUs will sometimes require cable extensions to properly work inside of an ATX PC case. It's a minor annoyance, not an expensive one. You might only need extra cable length for a few components, but it's worth checking before you fully commit to your build. Obviously if you're building in a smaller case it isn't an issue. It's always good to check the dimensions of your case though.