
The Corsair SF850L is an 850W fully modular, SFX-L form factor, ATX 3.1 power supply. It offers a single hybrid fan mode and was launched with a MSRP of $179.99 USD. Though the SF850L is now ATX 3.1 compliant, Corsair retained the previous model number and packaging, creating some marketing inconsistencies, as many materials still describe it as ATX 3.0 compliant. The power supply also lacks Under Voltage Protection (UVP), listing Catastrophic Failure Protection (CFP) instead, a standard feature not typically highlighted as a selling point.
While Corsair advertises the SF850L as 80PLUS Gold, it is certified Platinum. Confirmed through a discussion with Corsair, they understand that there can be variance between samples, therefore conservatively marketing this power supply as Gold. Overall, the power supply is solid across the board, with especially high marks for efficiency and load regulation, making it an ideal choice for users focused on compact and efficient builds.
WHAT YOU NEED TO KNOW
THE GOOD
- Load Regulation
The power supply demonstrated very minimal changes in output voltages even with increased load, ensuring consistent performance.
- Efficiency
It borders between 80PLUS Gold and Platinum, offering higher efficiency than its price would suggest.
- Form Factor
As an SFX-L form factor power supply, it is longer than standard SFX models but remains a great choice for compact builds, including an adapter bracket for easy compatibility with ATX-supported cases.
THE BAD
- Marketing Discrepancies
Corsair’s marketing materials for this power supply are inconsistent, leading to some confusion. The SF850L is labeled as ATX 3.1-compliant, but Corsair has only updated select parts of its website to reflect this change.
- Protections
It lacks UVP, relying instead on CFP, which should be a standard rather than a marketed feature.
THE REST
- Overall
The SF850L didn't perform exceptionally in every test but still maintained solid results overall. Its dependable load regulation and high efficiency make it a strong recommendation for users needing a reliable power supply.
The Corsair SF850L's SFX-L form factor makes it slightly longer than typical SFX units but keeps it suitable for tight spaces. In the Box, the unit comes with minimal accessories, such as Zip-Ties, an SFX to ATX Mounting Bracket, and Cables. The moderately flexible cables include a 12V-2x6 connector and use smaller "Corsair Type 5 Gen 1 micro-fit" connectors for compactness.
For cooling a 120 mm Fluid Dynamic Bearing fan ensures effective heat dissipation. The power ratings and specifications are consistent with expectations for this price range. On the Corsair specifications webpage it specifies that the Operating Temperature is up to 40°C, though we cannot verify this through testing.
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Front of the box.
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Power input side of the PSU.

Top of the PSU displaying the fan.

Side of the PSU displaying the specifications.
+12 V | +5 V | +3.3 V | +5 Vsb | -12 V | |
---|---|---|---|---|---|
CURRENT | 70.8 A | 20 A | 20 A | 3 A | N/A |
WATTAGE | 850 W | 150 W | 15 W | N/A | |
850 W |
Please note that the above ratings are manufacturer advertised specifications.
The SF850L includes a single hybrid fan mode, which ensures the fan does not spin until necessary, reducing noise during light loads. This mode, however, is not switchable.
In terms of protections, this unit does not come with the aforementioned UVP, but rather replaces it with CFP. The power supply is backed by a 7-year warranty.
The SF850L delivers solid overall performance, particularly in load regulation, where it shows impressive stability, especially on the 12V rail, with only a 0.073 V drop under full load. Voltage ripple is higher than ideal for 115 V input but is better controlled for 230 V. The peak-to-peak ripple on the fully loaded 12V rail reached 39 mV, while the 5V and 3.3V rails registered 43 mV and 46 mV, respectively.
An interesting aspect was noted during the 1.0 ms excursion tests. Here, the 12V rail displayed minor oscillations, which, while within acceptable limits, are unusual and only appeared at the 180% of rated load excursion. These oscillations did not occur at any other load level, so they are not an issue but are noteworthy given their isolated appearance. The power supply did face challenges with some prolonged excursions but met ATX specifications for all shorter-duration excursions.
The SF850L does not have a -12V rail, therefore there are no results for this rail.
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While marketed as 80PLUS Gold, the SF850L achieved Platinum in our efficiency tests, reaching 92% efficiency at 50% load. It balances between Gold and Platinum but provides above-average efficiency for its price. During brownout tests, it maintained output stability for 19 ms and 18 ms brownouts at 115V and 230V respectively, this is good performance for SFX/SFX-L power supplies.
The OCP triggered at 114% of the rated load, engaging at 140-160% on other rails, and there's no -12V rail. This is lower than similarly rated power supplies ensuring protection of the components but may result in the occasional shutdown during extremely high loads.
