The 5 Best SFX Power Supplies in 2023

Written by Azzief Khaliq
Last updated Feb 10, 2023

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SFX power supplies

Making sure your parts fit is one of the most taxing parts of building a small form factor (SFF) PC. Thankfully, you don’t have to do that with the PSU, as SFX and SFX-L power supplies are designed expressly for these small cases. But that doesn’t make identifying the best SFX power supplies any easier.

Even though there are fewer SFX power supplies on the market, you’re still dealing with varying levels of electrical performance and overall quality. And with SFX power supply prices the way they are, getting the best SFX power supply the first time is crucial if you want to avoid wasting time and money. So we’ve picked out five excellent power supplies for you to choose from. Let’s get started!

Short on Time? The Best SFX Power Supplies at a Glance
  • Best SFX PSU Overall: Corsair SF750 performs brilliantly in almost every important metric and has a great seven-year warranty backing it up.
  • Best SFX PSU Alternative: Corsair SF600 has even better electrical performance than its larger sibling and outclasses every other PSU in this power range.
  • Best High-Wattage SFX PSU: Cooler Master V850 SFX Gold packs a lot of power into a small package and performs solidly while it’s at it.
  • Best Budget SFX PSU: SilverStone ST45SF has decent enough performance and a good sub-$100 price for more modest SFF builds.
  • Best Silent SFX PSU: SilverStone NJ450 is a high-performance SFX power supply with a fanless design for silent operation.

Our Favorite SFX power supplies

Before we start, we should explain some common PSU terminology you’ll encounter on this list. These aren’t the only terms and metrics to pay attention to, but we’ve opted to focus on these to keep our overviews concise. See the full reviews we’ve linked if you need more thorough info.

  • Efficiency refers to how much power the PSU draws from the wall to supply a given amount of power to your components. Higher efficiency means a smaller difference between how much power the PSU draws and how much it outputs. For example, a 50% efficiency PSU pulls 1000 watts from the wall to generate 500 watts. In contrast, a 90% efficiency PSU only needs about 555 watts to generate that same 500 watts. Power supplies are more efficient at 230 volts than at 110 volts.
  • Load regulation measures how consistently the PSU can generate the voltages that a computer needs, regardless of load and what’s going on at either end of the connection. The lower the deviation from the on-paper voltage (12 volts, 5 volts, 3.3 volts), the better for stability.
  • Ripple measures the minute variations in a PSU’s DC voltage rails (the ones that go to your components). All PSUs will have some ripple, but the best ones will keep it well below the recommended limits of 120 mV on the 12-volt rails and 50 mV ripple on the 5-volt, 3.3-volt, and 5VSB rails. High amounts of ripple can shorten component longevity and impact overclocking, so you want as little ripple as possible.

1. Corsair SF750

Best SFX PSU Overall

Wattage 750 Watts
Efficiency80 Plus Platinum
ModularityFully Modular
Form FactorSFX, ATX (with included adapter)

If you need an SFX power supply to power your high-end compact gaming rig, look no further than the Corsair SF750. It’s one of the pricier SFX power supplies on the market, but its rock-solid performance more than justifies the extra cost over its rivals.

The Corsair SF750 excels at almost every metric or measurement you can look at to evaluate a power supply. TechPowerUp’s review shows it’s an incredibly efficient power supply across various loads, especially at 230 volts.

In their testing, the SF750 exceeds 90% efficiency from around 100 watts onwards, never dipping below that throughout the testing range. It even manages to stay above 90% efficiency when hit with an 800-watt load, which is impressive. Efficiency at 115 volts isn’t as impressive, but it’s still solid and overall justifies its Platinum efficiency rating.

Corsair SF750 efficiency

Source: TechPowerUp

Unlike Corsair’s lower-wattage SFX power supplies, you also get enough connectors to take advantage of all that power. You get two EPS, two PCIe, and two SATA power cables on the SF750; you’ll likely run out of wattage before you run out of power connectors for all your devices. The SF750 has enough connectors to power a tricked-out ATX rig, too, and Corsair even includes an SFX-to-ATX adapter if you want to run it in place of an ATX power supply.

The SF750’s load regulation is also outstanding. The 12-volt rail only deviated by 0.12% during testing, with only the 5VSB rail breaking past the 1% mark. The SF750 is in a class of its own here, with only Corsair’s other SFX power supply units keeping it company. For context, SilverStone’s SX700-G, still a decent SFX power supply, recorded deviations of 1.17% and 2.77% in the same tests.

Corsair SF750 Platinum load regulation

Source: TechPowerUp

Ripple control on the SF750 is also top-notch, generally staying at less than 30% of the recommended limits on all measurable rails. Ripple increases noticeably at 100% and 110% load, but it’s still well below 50%. That said, if you expect to hit your power supply with 700-750-watt loads regularly, you should probably be considering 850-watt or higher power supplies instead.

The Corsair SF750 is a semi-passive PSU, so it’ll run silently during low-load situations. The fan kicks in at about 40% (300 watts) and ramps up steadily from there. The SF750’s 92-mm fan won’t be audible above your case’s other fans in most situations, although high (> 40° Celsius) ambients may push it above 40 dBA at near-maximum loads.

Overall, there’s really no competition here: the Corsair SF750 is the best SFX power supply if you need a lot of power. Its roughly $190 MSRP is expensive for a PSU, but there’s no denying that you get what you pay for and then some. And if the performance wasn’t good enough, Corsair also backs it with a great seven-year warranty for peace of mind.

2. Corsair SF600

Best SFX PSU Alternative

Wattage 600 Watts
Efficiency80 Plus Platinum
ModularityFully Modular
Form FactorSFX, ATX (with included adapter)

Corsair’s SF750 rules the roost for high-watt SFX power supplies, so it’s not surprising that its little brother, the SF600, does the same in the ~600-watt bracket. If you’re building an upper-mid-range rig and want a high-quality PSU, the Corsair SF600 is the unit to get.

The Corsair SF600’s strengths are mostly identical to its bigger brother, the SF750. You get good efficiency befitting its 80 Plus Platinum rating, strong load regulation, excellent ripple suppression, and generally strong performance elsewhere.

Tom’s Hardware tested the SF600 at both 115 and 230 volts and recorded solid efficiency numbers at both voltages. The SF600 performs better at 230 volts, staying above 90% efficiency throughout the standard test range starting from 100 watts. It’s slightly less impressive at 115 volts but offers more than 90% efficiency for most of the range, only dipping under that mark at 500 watts and higher.

Sub-100-watt efficiency is solid too, with the SF600 hitting 88% efficiency at an 80-watt load and a still-impressive 82.6% efficiency at 40 watts. Most manufacturers focus on efficiency within the standard 80 Plus test range (which starts at 100 watts), so it’s great to see that Corsair hasn’t ignored idle power efficiency.

Load regulation is excellent, besting even the SF750. The SF600 offers less than 0.5% deviation on the 12, 5, and 3.3-volt rails. The SF600’s 0.12% deviation on the 12-volt rail and 0.10% deviation on the 5-volt rail is particularly impressive and beats out other similar-wattage units without issue.

Ripple suppression is much the same, with maximum ripple staying below 25% of the recommended maximums of 120 mV on 12-volt rails and 50 mV on 5-volt, 3.3-volt, and 5VSB rails. The 12-volt rail is particularly impressive, only significantly exceeding 25 mV of ripple at 110% of maximum load.

If you’re building a mid-powered SFF rig, there really isn’t a better power supply choice than the Corsair SF600. No, it’s not perfect, but it’s still the best SFX power supply in this wattage range. If you want an SFX power supply that’s almost guaranteed to run safely and reliably, get this.

3. Cooler Master V850 SFX Gold

Best High-Wattage SFX PSU

Wattage 850 Watts
Efficiency80 Plus Gold
ModularityFully Modular
Form FactorSFX, ATX (with included adapter)

Our top pick should have more than enough power for most SFF rigs, especially considering the usual space constraints of a Mini-ITX case. However, if you’re cramming some power-hungry hardware and need a little extra juice, Cooler Master’s V850 SFX Gold should have you covered.

The V850 is “only” an 80 Plus Gold PSU, as opposed to the 80 Plus Platinum of Corsair’s SFX power supplies. That bears out in the testing: The FPS Review tested the V850 at 120 volts and recorded efficiency percentages ranging from 90.12% (50% load) at best to 87.07% (roughly 100% load) at worst. Acceptable performance for a Gold-rated PSU, although nothing to shout about in a market populated by Platinum-rated SFX power supplies.

Load regulation is solid, with relatively minor deviations detected on the 12, 5, and 3.3-volt rails. The deviations are generally in the 1.5% range, which is perfectly fine. We would love to see sub-1% results here, but these numbers won’t pose any threat to your hardware. It’s a stable power supply that you won’t have to worry about.

The V850 fared noticeably better in The FPS Review’s ripple testing, with ripple on all measurable rails sitting at 30% or less of the ATX standard. The V850 managed to keep the 12-volt rail’s ripple below 25 mV, which is great. The 5-volt and 3.3-volt rails fared equally well, with roughly 15 and 10 mV of ripple, respectively.

Cooler Master V850 SFX Gold SFX PSU

A Cooler Master V850 SFX Gold PSU. Source: Cooler Master

Like many modern PSUs, the V850 has a semi-passive design that keeps the fan off below 15% load. This eliminates fan noise when idle or when you’re doing simple tasks like browsing the internet. The fan will become noticeably audible once you hit 75% load or higher, but that’s par for the course with such small fans.

The Cooler Master V850 SFX Gold isn’t necessarily the best SFX power supply unit out there, but its good performance and ten-year warranty make it a wonderful option if you need a seriously powerful SFX power supply The V850 SFX Gold is also available in white.

4. SilverStone ST45SF

Best Budget SFX PSU

Wattage 450 Watts
Efficiency80 Plus Bronze
Form FactorSFX, ATX (with included adapter)

High-wattage SFX power supplies are impressive, but not everyone needs one. They’re total overkill if you’re building a more modest and budget-oriented SFF rig. Whether a living-room HTPC or a simple dorm room rig for low-end gaming, SilverStone’s ST45SF has enough power and performance to cover most budget SFF builders’ needs.

The ST45SF is a 450-watt, non-modular power supply with an 80 Plus Bronze rating, giving you a good idea of what to expect here. It won’t impress anyone with its efficiency or ripple suppression, but it’ll do a decent job at a wallet-friendly price. If you’re on a budget, that matters more than outright electrical performance.

Tom’s Hardware’s testing shows that efficiency is under 90% across the range, regardless of input voltage, and dips noticeably the closer you get to maximum output. It barely makes the 80 Plus Bronze grade at 115 volts, but that’s not a massive issue unless you live somewhere with brutal electricity costs. However, it reflects the ST45SF’s budget nature, which carries through to the other power supply metrics such as load regulation and ripple.

Load regulation is mediocre but decent enough for the price. The 12-volt rail performs decently enough, with only a 1.22% deviation, but the minor rails fare noticeably worse. The 3.3-volt rail’s 2.46% deviation and the 5VSB rail’s 3.19% deviation are particularly unimpressive. Still, neither is critical enough to pose any danger to your rig.

The ST45SF’s ripple protection is decent, staying around or under 50% of ATX spec on all rails through most of the PSU’s output range. The only major issue is the 3.3-volt rail, which hits a peak of 41.4 mV of ripple (just shy of the 50 mV allowed) at 90% load.

However, it’s worth noting that Tom’s Hardware tested the ST45SF with a 46° C ambient temperature. It’s on the high side and not ideal for a cheaper power supply like the ST45SF. It’s still safe, of course, but it’ll likely fare better in a cooler, better-ventilated case.

Overall, the SilverStone ST45SF is a decent, if unspectacular, SFX power supply designed for one thing: reliable power delivery at a low price. It can’t compete with the best SFX power supplies, but the ST45SF will do a good job and is probably the best SFX power supply under $100.

5. SilverStone NJ450

Best Silent SFX PSU

Wattage 450 Watts
Efficiency80 Plus Platinum
ModularityFully Modular
Form FactorSFX-L

SFF PCs are perfect for living-room rigs due to their small size, but a living-room HTPC has different requirements than the average gaming rig. One of the main criteria is silent (or near-silent) operation, which is where a passive PSU like the SilverStone NJ450 comes into its own.

The SilverStone NJ700 is a fully passive, 450-watt SFX power supply with an 80 Plus Platinum rating. It’s an impressive unit, not least because SilverStone managed to pull off a reasonably powerful passive PSU in this constrained form factor. It’s not necessarily a home run, but it gets a lot of things right.

Silverstone NJ450 efficiency

Source: KitGuru

Efficiency is great here, mostly meeting the 80 Plus Platinum requirements at 115 and 230 volts, based on KitGuru’s testing. They recorded an average efficiency of 90.63% at 115 volts and 91.74% at 230 volts, making this one of the most efficient 450-watt SFX power supplies you can buy.

Load regulation is also solid, with the 12-volt rail and all minor rails staying relatively close to their nominal values. Deviation on the 12-volt rail is particularly impressive, sitting at 0.28%. The minor rails don’t fare quite as well, but 1.21% and 1.81% on the 5- and 3.3-volt rails, respectively, are still great and above average.

SilverStone NJ450 load regulation

Source: KitGuru

The NJ450 has excellent ripple control. The worst-case measurement of ~18 mV on the 12-volt rail stays well below the ATX specification limit, while the 5- and 3.3-volt rails also showed solid ripple suppression. Ripple only increased noticeably once KitGuru pushed the NJ450 to 100% and 110% load, which shouldn’t happen in daily use. You’ll be safe here.

Overall, the SilverStone NJ450 is an impressive SFX power supply with good electrical performance and zero noise. The value proposition is a bit problematic considering its $200 asking price and short three-year warranty, but those seeking absolute silence from their SFX power supply won’t have much choice.

Before You Buy

Shopping for an SFX power supply is complicated, but no more complicated than buying a power supply unit in general. So if you’re curious about how to choose a power supply unit, you can check our guide to choosing a PSU. Here, we’ll stick to discussing an SFX-specific topic, namely the minor differences between SFX and SFX-L PSUs.

ATX, SFX-L, and SFX PSUs side-by-side

There are two compact power supply form factors, SFX and SFX-L. As the shared naming suggests, the two are more similar than they are different. Both are 4.92 inches wide and 2.5 inches tall but differ in length. SFX power supplies are 3.93 inches long, while an SFX-L power supply will be 4.92 inches long.

Generally, most compact cases will support SFX and SFX-L power supplies, with the choice between the two entirely up to you. However, some ultra-compact mITX cases, like the SGPC K49, only have room for SFX power supplies. So, check and double-check before buying your PSU, especially if you’re building in a small Mini-ITX case.

Closing Thoughts

Just because you’re forced to use an SFX power supply in a small form factor rig doesn’t mean you should settle for any old PSU and just slam it in there. Sure, you may have fewer options, but looking for the best SFX power supplies is much like any standard PSU: pay attention to the electrical performance, efficiency, and wattage, and you should be set.

If you need a lot of power, there’s no looking past the Corsair SF750. It’s likely the best SFX power supply out there, and comes with one of the better warranties too. If you don’t need that much power, the SF600 is equally good and a strong candidate for mid-power builds.

All the best!

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