Many people who are building a PC for the first time are not sure whether to get an ATX or SFX power supply. In this article, I will compare the two types of power supplies and help you decide which one is right for you.
ATX and SFX are the two most common types of power supplies for desktop computers. ATX power supplies are larger and more powerful, while SFX power supplies are smaller and less powerful.
Brief Comparison Between ATX & SFX PSUs
Here, I have compared ATX and SFX power supplies based on six different factors:
Form Factor Comparison (Physical Dimensions)
ATX and SFX are the two popular PSU form factors, and they have different physical dimensions.
| Form Factor | Width (mm) | Height (mm) | Depth (mm) |
| ATX | 150 | 86 | 140 |
| SFX | 125 | 63.5 | 100 |
You can see in the table above that SFX power supplies are smaller than ATX power supplies.
If you are building a traditional ATX PC, then get an ATX power supply. But if you’re building a smaller PC (SFF), you’ll need to buy an SFX power supply.
Wattage & Efficiency Of ATX & SFX PSU
There is no significant difference in efficiency ratings between ATX and SFX power supplies. Both form factors can achieve 80+ Platinum or even Titanium efficiency ratings.
However, the ATX PSUs are available between 300 to 2000 wattage range, whereas the SFX PSUs are available between 300 to 1000 wattage range.
Additionally, SFX power supplies have fewer connectors than ATX power supplies. So, if you have a lot of components to power, then you may need to use adapters with an SFX power supply.
Space Consideration
Compared to the physical dimensions of the ATX Power Supplies, the SFX Power Supply is about 20% smaller in terms of volume.
ATX power supplies are bigger, so you need a bigger PC case to install them. SFX power supplies are smaller, so you can use them in smaller PC cases.
Cooling & Noise
Compared to the SFX Power Supplies, the ATX PSUs have large fans, and therefore, they can move more air and keep the Power Supply cooler.
Additionally, the ATX Power Supplies are also quiet compared to SFX PSUs because they have larger fans that can spin at slower speeds while still moving the same amount of air.
ATX power supplies are better at cooling and are usually quieter than SFX power supplies. But SFX power supplies are smaller and more compact, so they are good for small computers.
Compatibility With Components
Both ATX & SFX Power Supplies are compatible with the same motherboards, graphics cards, and storage devices.
The only difference is that some SFX Power Supplies have fewer connectors compared to ATX PSUs; therefore, you may need to use adapters to connect all of your components. However, most SFX power supplies come with all of the necessary connectors.
Additionally, if you want to use RGB lights or extra fans, then it’s better to use an ATX Power Supply.
Price
SFX PSUs are typically more expensive than ATX PSUs due to their smaller size and more complex manufacturing process.
However, the price difference has narrowed in recent years as SFX PSUs have become more popular and more manufacturers have entered the market.
Here’s a price comparison of a few popular ATX and SFX PSUs from different manufacturers:
| Power Supply | Wattage | Form Factor | Price |
| Corsair RM750x | 750W | ATX | 100$ |
| be quiet! Pure Power 11 FM | 750W | ATX | 120$ |
| Silverstone SX700-G | 750W | SFX | 140$ |
| Corsair SF750 | 750W | SFX | 140$ |
Pros & Cons Of ATX And SFX Power Supplies
Here is a table that clearly explains the distinctions between ATX and SFX power supplies, along with their pros and cons.
| Feature | ATX PSU | SFX PSU |
| Size | Larger | Smaller |
| Weight | Heavier | Lighter |
| Wattage Options | Wider Range | Narrower Range |
| Compatibility | More Widely Compatible | Less widely compatible |
| Price | Generally less expensive | Generally more expensive |
| Noise | Can be noisy under load | Generally quieter than ATX PSUs |
| Efficiency | Less efficient under load | Can be noisy under a load |
Should You Choose An ATX Or SFX PSU?
Whether you should choose ATX or SFX Power Supply depends on the size of the PC Case. ATX power supplies are the most common type and are compatible with most PC cases.
On the other hand, SFX power supplies are smaller and are designed for smaller, more compact PC cases.
| PC Case Types | Compatible PSU Types |
| Full Tower | ATX |
| Mid Tower | ATX |
| Mini Tower | ATX and SFX |
| SFF (Small Form Factor) | SFX |
If you have a Full Tower or Mid-Tower PC Case, then go for an ATX power supply. However, if you have an SFF PC Case, then you should choose an SFX Power Supply.
Only a Mini-Tower PC Case can fit both ATX and SFX Power Supplies without any issues.
If you want to install an SFX PSU in larger PC cases like Full-Tower or Mid-Tower, you will need an adapter or bracket. Read this article to know how you can install SFX PSU in ATX PC Cases.
However, if you prefer a smaller and lighter power supply with more portability, then you should opt for the SFX Power Supply.
If you’re looking for a budget-friendly power supply with more power, extra connectors, and improved cooling, then you should go with an ATX PSU.
Also, if you’re using different types of power supplies, such as TFX or Flex ATX, and you’re wondering which PC cases will work with these power supplies, then check out this article to find out which PSU fits in which PC cases.
If you have any more questions about building a PC or PC hardware, please ask me in the comments below.
