Two ways PSU noise gets rated
Either the maker prints decibels, as be quiet! and SilverStone do, or the unit carries a noise grade from Cybenetics, an independent lab.
be quiet! and SilverStone print numbers
Every be quiet! unit comes with a four point curve: dB(A) at 10%, 20%, 50% and 100% load. No other category we have covered discloses as much, because the curve tells you what the thing sounds like at the load your machine actually sits at. SilverStone prints single numbers instead, "0 dBA" for its fanless units or "18 dBA min." for the Attis 750x.
Cybenetics grades convert to decibel bands
Seasonic, Corsair, ASUS, FSP and XPG print a letter from Cybenetics, which measures noise across the load range and averages it; Corsair explains the method on its pages. Because the scale is published, the letter converts to a band. FSP reprints it in full beside its grade:
| Grade | Average noise |
|---|
| A++ | under 15 dB(A) |
| A+ | 15 to under 20 |
| A | 20 to under 25 |
| A- | 25 to under 30 |
| Standard++ | 30 to under 35 |
| Standard+ | 35 to under 40 |
| Standard | 40 to under 45 |
A graded unit therefore gives you a band, measured by someone who is not selling it. Set against a bare maker number with no distance and no load point, that is a decent trade.
The name on the box is not the grade
Corsair sells the SF1000L as a "Low-Noise SFX Power Supply", and it is the loudest graded unit in this guide. Its Cybenetics grade is Standard+. That is at least 35 dB(A) and under 40. No other unit here has "low noise" in its product name.
Cooler Master's X Silent Edge Platinum 850 makes the same point from the other side. The name promises silence; the specification table publishes neither a decibel figure nor a grade.
Read the grade or the number, never the name.
Is a higher wattage power supply louder?
At full load in be quiet!'s range, yes. The 550W Pure Power 13 M publishes 14 dB(A) at 100% load, and the 1300W Dark Power Pro 13 publishes 23.2. The first is the cheapest unit here and the second the most expensive.
The big unit is not faulty. A 1300W supply at full load moves far more heat than a 550W one, and it holds 10.2 dB(A) all the way from 10% to 50% load, which is where a real machine spends most of its time. A larger unit does spend more of its life at low load, and that helps. Still, buying more wattage than you need does not automatically buy quiet, and at the top of the curve it buys the opposite.
Is a fanless power supply silent?
No. Coil whine and transformer buzz remain, and the two fanless makers here describe their units very differently.
Seasonic's PRIME Fanless TX-700 carries a Cybenetics A++ noise grade. A unit with no fan still gets measured, because the lab picks up those electrical sounds, and A++ means the average came in under 15 dB(A).
SilverStone's Nightjar NJ700 publishes "Noise Level 0 dBA" with no load point, no distance, no ambient temperature and no standard. Taken literally, that says the unit emits no sound at all.
Nothing does.
Both are fanless, and only Seasonic's figure was measured. A fully passive build needs a passive CPU cooler too, and our CPU cooler guide includes a fanless heatsink.
The noise rows on Corsair's PSU pages belong to its coolers
Corsair publishes no decibel figure for any PSU in its range. Its power supply pages do, however, embed cross-sell blocks for its coolers, and those blocks carry their own "Noise Level" rows, such as "10 - 36 dBA". Read quickly, or scraped automatically, that number looks like it belongs to the power supply. It does not.
