I've built many computers over the years, and picking the best PSU can make or break the experience. Every little bit of space matters for small form factor (SFF) builds, so finding a slim power supply and prioritizing a modular setup is critical. Compared to your average ATX PSU, SFX power supplies are tiny but not necessarily cheaper if you don't search far and wide enough.
Luckily, I've already worked to round up the best SFX PSU to fit your next slim build. They still fit inside most full-tower desktop cases, offering more versatility if you need to power multiple machines with the same unit. Naturally, you'll need to match the total potential wattage on your chosen PSU with whatever components will be inside your new PC, so consider the power draw of each part and pick a suitable equivalent.
It's always wiser to go a little higher than you need, future-proofing any updates you might not have considered yet. Here are my picks for the best small form factor power supplies, suitable for various budgets and wattage requirements.
Best overall
Impressing in our SilverStone SX700-PT review, this PSU proved perfect for mid-range GPUs within a compact case. At 700W, it'll handle most builds, but it's also available in 750W and 1000W variants if you're going higher.
Runner-up
Still one of the most popular SFX power supplies, the Corsair SF range is a fantastic alternative. Boasting a seven-year warranty should leave you with no reservations about whether Corsair believes in the quality of its products. It comes in a range of wattage variants, all slim and compact.
Third alternative
Coming in at a close third is the slim SFX PSU from FSP, similarly impressing in Rich Edmond's Dagger Pro 850W review. Performing a little louder than its counterparts, it uses quality components and won't stand out as noisy during normal operation.
Budget-friendly
Another with a seven-year warranty, the SuperNOVA GM includes an SFX to ATX bracket should you want to fit this PSU into a larger case. EVGA keeps the fan noise low and the price down with this hugely affordable SFX power supply.
Budget substitute
Closely matched at its price to the budget choice but operating a little louder, the Ion SFX range is a fantastic alternative for saving money. Includes a free SFX to ATX bracket and 80+ Gold-rated efficiency.
Cool and quiet
Yet another fully modular choice for the SFX form factor, the FOCUS SGX includes a free ATX adapter mount and a massive 10-year warranty, generous indeed. Pushing the cost up a little from our budget choices but well worth the jump considering its high-quality construction.
How much wattage do I need?
Each component inside your PC draws a certain amount of power from your PSU, and you'll need to provide at least the minimum wattage required to keep things running smoothly. Popular websites like the PCPartPicker builder offer a rough calculation based on the parts you select, but it isn't a guaranteed result. Still, it's better than nothing and should give you an idea of where to start. When in doubt, go 100-150W above your calculated total.
Choosing the best SFX PSU for your compact PC
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Just because they're smaller, it doesn't mean SFX power supplies are necessarily weaker than their full-sized ATX variants. Generally designed for more compact cases, it is possible to mount an SFX PSU with an adapter into an ATX case. Besides their physical size, they do the same job: provide your components power at whatever total wattage they need. It's worth double-checking your case requirements because SFX power supplies are usually only ever selected for the tiniest builds.
Once you've decided which PSU standard is best for your PC, you can choose which is best for you. Our collection of SFX styles is well suited for a small form factor PC, and there are plenty of other size choices when looking for the best power supply in general.
