Corsair SF850L SFX-L PSU Review – The BEST SFX-L PSU


The Corsair SF850L is the performance king in the small form factor categories, taking the lead from its more powerful brother, the SF1000L, which achieves second place. With only 20 dollars price difference between these units, it will be a tough decision, but I will make it easier for you. In essence, the SF850L is an SF1000L unit with 150W less. The fan speed profile is identical at up to 850W load in both models, but the stronger unit provides you with 150W more should you need it. The SF1000L also has a slightly better transient response at 200% load, but it loses overall performance because of its higher capacity, which is the limiting factor in all tests. Generally, when you have two identical platforms, you can expect higher overall performance from the lower-power one because it has less road to cover. Imagine it like this, we put two runners sharing the same capabilities to cover two distances, a longer and a shorter one, so it is easy to guess the winner. In my overall performance calculation algorithm, I consider the PSU’s capacity, of course, else lower capacity units would score top places, but still, in some cases, the higher performance in other sections overcovers it. In this case, the SF850L achieves notably better load regulation than the SF1000L, and it has a longer hold-up time, higher efficiency, and lower vampire power.

With a less aggressive fan speed profile, the SF850L will be even better, but this has to be done correctly, as not to affect the platform’s reliability at increased operating temperatures. Usually, OEMs have a tough time tuning fan speed profiles since they don’t follow the proper testing approach as they do in Cybenetics, where they apply thousands of different load combinations to extract the complete noise map.

If 850W are enough for your system, the Corsair SF850L is the ideal PSU unless you need a dead silent product. I would go for the SF1000L to have more headroom and an extra dedicated 6+2 pin PCIe cable since the price difference is slight at 20 dollars.


To check all alternative PSU offerings, read my Best ATX v3.0 PSUs article before investing in a new power supply. You help me a lot by using my affiliate links, which don’t increase the product’s price. I get a commission from Amazon every time you do it, which can make a difference for me, especially now that I am on my own, working exclusively for my media and not for someone else.





  • Top performance
  • Top build quality
  • Good price
  • ATX v3.0 and PCIe 5.0 ready
  • Top transient response
  • Properly configured OCP at 12V and OPP
  • Efficient
  • Highly efficient 5VSB rail
  • Tight load regulation
  • Goold ripple suppression
  • Long hold-up time
  • Accurate power ok signal
  • Low vampire power
  • Alternative Low Power Mode (ALPM) compatible
  • Fully modular
  • Enough connectors, including a 12VHPWR (600W)
  • Fluid dynamic bearing fan
  • SFX-to-ATX adapter bracket provided
  • Seven-year warranty
  • Noisy at above moderate and at high loads
  • High OCP triggering points on the minor rails
  • PF readings could be higher



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6 thoughts on “Corsair SF850L SFX-L PSU Review – The BEST SFX-L PSU

  1. Is the included 12VHPWR cable sufficient/safe for powering an RTX 4090 FE or should a 3×8 cable/adapter still be used? If it is sufficient and totally safe, does the manual specify which ports to use or doesn’t that matter?

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