Best Seasonic SFX power supply units reviewed and compared

Seasonic is one of the leading brands in the SFX power supply segment thanks to several key advantages. First, we’ve been making high-quality PSUs for ourselves and other brands (like Corsair) for 50 years. We guarantee the high reliability of all Seasonis PSUs series and pay great attention to every detail while designing them. As a result, you get a powerful engine that brings your PC’s performance to the highest level.

Second, we guarantee high-quality components and use innovative technologies to create PSUs. To do this, we use high-end Japanese capacitors, hybrid (Silent/Hybrid) cooling systems, and multi-level protection against failures. Next, we offer the longest warranty periods on the market – 12 years for the PRIME and VERTEX series, 10 years for the FOCUS series, and 7 years for the CORE series.

The high-quality SFX models (SPX and SGX) got high ratings in user reviews. With the hybrid mode, you don’t have to worry about noise at low loads. The power supply is stable under high loads, thanks to 80 PLUS® Platinum certification.  

What are the key features of Seasonic’s latest SFX and SFX-L models?

The latest SFX and SFX-L models in Seasonic’s FOCUS series (SPX and SGX) stand out in the market for one simple but essential reason. They live up to Seasonic’s consistently high quality standards. Add some details. 

Seasonic Focus SPX (750 W and 650 W, SFX form factor)
Designed for compact but powerful builds. These fully modular PSUs come in a small package (125 × 100 × 63.5 mm). The Silent Hybrid Fan Control system operates in three stages: the fan stays off at low loads, runs quietly at mid-load, and ramps up only when needed under full load. Full control to bring you joy while working or gaming on PC. You also get 80 PLUS® Platinum efficiency, precise voltage regulation, and an SFX-to-ATX bracket for wider case compatibility.

Seasonic Focus SGX (750–550 W, SFX-L form factor)
A slightly larger form factor (125 × 125 × 63.5 mm) allows this model to include a 120 mm fan for even better airflow. Like the SPX, it features the same hybrid cooling, full modularity, and a 10-year warranty. It’s 80 PLUS® Gold certified and offers tight voltage regulation (±0.5%). All these make it a reliable choice even for demanding systems.

How do Seasonic SFX units compare in terms of efficiency and certification?

Seasonic FOCUS SPX (650W and 750W, SFX format) is certified to the 80 PLUS® Platinum standard. This means it delivers approximately 92–94% efficiency at 50% system load. For example, during long-term operation, overclocking, or gaming. When it’s the highest system load, it provides 90% efficiency. Impressive result for compact PC power supply. 

Seasonic FOCUS SGX (450–750 W, SFX-L format) is 80 PLUS® Gold certified. This certification guarantees at least 90% efficiency at 50% load and up to 87% at maximum load. The FOCUS SGX-650, with the same certification as the SGX-750, provides up to 92.5% efficiency at average load and about 90.5% at full load.

The key difference between the two models is the certification level. Platinum for the SPX vs. Gold for the SGX. The real-life tests prove that the SPX consumes less energy and emits less heat, especially at medium loads.

Which Seasonic SFX PSU is best for high-performance mini-ITX builds?

For high-performance mini-ITX builds, there are two best SFX power supply options from Seasonic. The FOCUS SPX-750 (750W, standard SFX) or the FOCUS SGX-650 (650W, SFX-L format). Make it clear about their features. 

The Seasonic FOCUS SPX-750 is fully modular and has a sleek, compact design. It has 80 PLUS® Platinum efficiency. Reviews note its excellent voltage stability and fast transient response, which is important for powerful CPUs/GPUs, and a 10-year warranty. Thanks to these specs, it is still a highly effective, powerful, and stable solution for compact, high-performance systems.

The Seasonic FOCUS SGX-650 has also received 5-star reviews for its combination of power, fully modular design, quiet 120 mm fan, and a 10-year warranty. We recommend choosing this option if your case allows for a deeper unit. It is an excellent choice with a quieter fan and a smaller size.  

What are the noise and cooling characteristics of Seasonic SFX PSUs?

Seasonic SFX/SFX-L computer PSUs have an effective hybrid cooling system. Quiet under medium loads, but becoming noticeably louder (40–45 dB) under heavy loads. 

The Seasonic FOCUS SPX-750 with a 92 mm fan has a more aggressive noise profile (~40 dB at ~250 W), while the FOCUS SGX-650 with a 120 mm fan provides quieter operation up to 340 W.

The key idea here is: If you need the quietest system possible, choose a model with a larger fan ( SGX) and pay attention to the case and cooling in your build. Everything should fit your PC perfectly to ensure maximum performance during working or game sessions. 

Are Seasonic SFX power supplies compatible with 12VHPWR and modern GPUs?

Yes, Seasonic SFX power supplies are compatible with today’s graphics cards that use the 12VHPWR (PCIe 5.0) standard. But only if you meet certain conditions.

Seasonic offers official 12VHPWR cables (straight and 90° angled) designed for connection to high-performance GPUs (up to 600W). To use them, the power supply must have at least two free 8-pin PCIe connectors with a power rating of 650 W or more. In this case, the PRIME, VERTEX, and FOCUS series models are perfectly fitted. 

Additionally, note that some models in the FOCUS (SPX/SGX) line have only one PCIe connector. Therefore, you need two separate outputs to work with 12VHPWR cables. This option is available in the larger FOCUS GX/GM/ATX models.

What do real users and pc builders say about Seasonic SFX reliability?

Here’s what PC community users and system builders think of Seasonic SFX power supplies.

• The SPX/SGX series receives high marks for stable performance in powerful configurations. Users highlight Seasonic SFX power supplies for their quiet operation and reliable performance under heavy loads. 
• Communities respond positively to the up to 12-year warranty, which makes the brand a trusted choice as well.  

Which Seasonic SFX power supply offers the best value for money in 2025?

The FOCUS SGX-650 PSU is considered to be the best value for money in the 2025 Seasonic SFX lineup. It costs around $120.

For this price, you get a fully modular power supply, built-in hybrid cooling, a 120 mm fan, an 80 PLUS® Gold rating, and a 10-year warranty from Seasonic. Reviews (RelaxedTech) call it “an affordable and quiet solution for compact systems.”

Conclusions

If you plan to buy a high-performance and reliable PSU that handles all your tasks, Seasonic has a lot of options to offer. All Seasonic SFX PSUs have 80 PLUS® certifications, meet all the tech standards, and have already proven their excellence in real-world tasks. Explore all the products at the Seasonic website and choose the power unit that will be with you for a long time.