When we tested the Corsair SF850L power supply, we noticed that both the box and Corsair's website said it was 80PLUS Gold certified. However, when we checked CLEAResult's database, it was actually rated as Platinum! Naturally, we reached out to Corsair to ask why.
Power Supply Efficiency Rating
But before we dive into Corsair's reasoning, here's a short and efficient overview of power supply ratings. You've likely come around terms like 80PLUS Bronze, Gold, and Platinum, or Cybenetics' Platinum, Titanium, and Diamond ratings. But what do these labels actually mean?
Starting with 80PLUS, this is a widely recognized performance certification for power supplies, managed by CLEAResult, an energy consultancy that supports organizations ranging from cities to transportation agencies. The 80PLUS certification is recognized by ENERGY STAR and the European Union and marks power supplies that achieve at least 80% energy efficiency at 20%, 50%, and 100% loads. CLEAResult's program includes six certifications levels: Standard, Bronze, Silver, Gold, Platinum, and Titanium, each represented by a badge indicating the power supply's efficiency rating.
Screenshot from “80 PLUS certification specifications and ratings | CLEAResult,” www.clearesult.com. https://www.clearesult.com/80plus/program-details
Cybenetics offers a similar certification program known as ETA, which enforces stricter testing criteria than 80PLUS. Cybenetics evaluates additional factors like voltage stability, ripple, power factor, noise, and temperature resilience. Cybenetics also has six efficiency ratings: Bronze, Silver, Gold, Platinum, Titanium, and Diamond, allowing users to assess a power supply's efficiency under more demanding conditions. You can read more about their methodology on the Cybenetics website.
Screenshot from “Cybenetics Labs – PSU Efficiency & Noise Level Certifications - ETA,” Cybenetics.com, 2022. https://www.cybenetics.com/index.php?option=eta_9-51-40
Both of these certifications indicate how efficient a power supply is, but high-rated models typically come at a premium price. In places where electricity costs are high, a more efficient power supply can save you money in the long run. Higher efficiency can also be a benefit in hot climates, as less heat is produced, helping keep the system cool and reducing fan noise.
So, what exactly is power supply efficiency? In simple terms, it's the ratio of power output to power input, usually shown as a percentage. This metric is generally specified at full load and nominal input voltage. Efficiency is calculated as follows, as illustrated by Sunpower Electronics:
Sunpower Electronics further explains,
If a power supply with 50% efficiency is required to provide a 50 W power to a load, it will draw 100 W from the wall. The other 50% gets wasted as heat and other losses. If a 90% efficient supply is used, it will draw 56 W to supply the same load, meaning that it has fewer losses and uses less power from the grid to provide the same output power.
Power supply efficiency isn't constant; it can fluctuate based on factors like load and environmental conditions. Typically, computer/ATX power supplies reach maximum efficiency around 40-50% load. As the certification level goes up, so does the price, but the added efficiency and longevity can justify the investment.
When choosing a power supply, look for one with either 80PLUS and/or Cybenetics certifications, as these validate that the unit meets tested efficiency standards. While neither certification is definitively better than the other, they assure you that the power supply has undergone testing and meets quality standards—a key consideration when aiming to avoid unexpected issues.
Corsair SF850L
Now, back to the Corsair SF850L. We wanted to make sure we had the right power supply model and that the marketing information was accurate. We found that Cybenetics rated this power supply as Platinum as well.
When we reached out to Corsair, they explained that it's not unheard of for power supply models to be marketed with a lower certification than what some units achieve in testing. They have done this before with the CX750 and CX750F. They decide on the certification level, such as Bronze or Gold, early in the design process, even before they send a sample to 80PLUS for testing. Since product packaging needs to be ready before production, Corsair tests dozens of samples and sets a baseline for performance. Although some units might reach higher efficiency levels, like Platinum, they stick with a lower certification, like Gold, because not all units will consistently meet the higher standard.
FSP Group VITA-850GM
Recently, we tested the FSP Group VITA-850GM power supply, which revealed some similarly interesting results. While it's marketed as an 80PLUS Gold unit, CLEAResult actually rated it at 80PLUS Platinum. Our own testing confirmed that the VITA-850GM met all Platinum efficiency standards except when running at a 230V input with a 50% load. It seems FSP Group is conservatively rating the unit as Gold, likely because not all units will consistently achieve Platinum performance.
Why is this significant?
Some manufacturers may send their best "golden samples" for testing, aiming to secure higher ratings. However, with the Corsair and FSP Group examples, it shows that even large companies know that not all units will perform the same, and they'd rather play it safe when it comes to marketing.
When we conduct efficiency tests, we are verifying whether a power supply's marketed claims align with real-world performance. Did the manufacturer send a hand-picked "golden sample", or is it a typical production unit? Even when we receive samples ourselves, there's always a possibility of getting one that performs slightly above average, which is part of the inherent variability in the testing process. Remember, cross-checking ratings with reports directly from organizations like CLEAResult or Cybenetics is a good way to determine if a power supply is actually as efficient as advertised—or if it falls short.
Want to learn more about the Corsair SF850L or the FSP Group VITA-850-GM? Take a look at our product pages for a more in-depth review.
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