SFX vs SFX-L Power Supplies
SFX-L is SFX made 30 mm deeper. Width and height are identical at 125 by 63.5 mm, and the mounting holes are the same, so the only question is whether your case has room for the extra depth. That depth exists for one reason: it fits a 120 mm fan instead of an 80 or 92 mm one, which is why SFX-L units are generally the quieter of the two.
If the case takes SFX-L, take SFX-L: the larger fan is the single most effective thing you can do about noise in a small build, and the price gap is usually small. If the case is SFX only, that settles it, and modern SFX units at a good noise grade are perfectly liveable. Always check the case specification, because plenty of compact cases accept only the shorter unit.
The physical difference
These are fixed standards, the same for every unit of that size.
Will it fit your case?
Two things the standard alone does not tell you.
The clearance figure is a second number
Your case names a power supply standard and, separately, a maximum depth. The standard says what can mount; the clearance figure says how deep a unit may actually be once the cable run and the drive cage are in the way. Both come from the case maker, and depth is the one people skip.
Cable length matters in small builds
Small-form-factor units ship with shorter cables because that is what a compact case needs. If you put one in a full-size case, check that the motherboard and CPU cables reach, since those two runs are the longest in any build.
The difference in practice
How the two actually differ across units you can buy today, rather than what the standard permits. Measured across 29 SFX and 13 SFX-L units with a live offer at the retailers we track, and updated daily.
Where we track fewer than 15 units on a side, the exact count is shown instead of a percentage: a rate off a handful of units would read as more certain than it is. Depth and noise are quoted against their own samples because neither is published for every unit, and assuming a figure for the ones that do not publish one would change the answer.
The picks on each side
The cheapest unit on each side, and the cheapest one that clears a bar worth clearing: at least 40 of 100 on the quality score. Recalculated daily from live prices.
SFX
SFX-L
Best all-round
$144.99 · 750W · the cheapest unit here already clears the bar
Affiliate disclosure: Some links on this page are affiliate links — MaxMyBuild may earn a commission at no extra cost to you if you buy through them. As an Amazon Associate, MaxMyBuild earns from qualifying purchases. For Amazon, current price and availability are shown on the Amazon product page; product prices and availability are accurate as of the date and time of purchase and are subject to change. Prices shown for other retailers are approximate and may differ at checkout. “Search” links are non-affiliate and provided for convenience only.
Common questions
Will an SFX-L PSU fit in an SFX case?
Only if the case explicitly lists SFX-L support or quotes at least 130 mm of clearance. The mounting holes line up, so it can look like it fits right up until the extra depth fouls a cable run or a drive cage.
Is SFX-L quieter than SFX?
Generally yes, because the extra depth makes room for a 120 mm fan rather than an 80 or 92 mm one. A larger fan moves the same air at a lower speed, which is quieter. The measured noise grade for the specific unit is still the number to check.
Can I use SFX-L in an ATX case?
Yes, with the same adapter bracket SFX units use. In a full-size case there is rarely a reason to, since an ATX unit will be cheaper per watt, but it works if you are reusing a unit from a previous build.
Keep going
Browse SFX units or SFX-L units with every filter, read up on how much wattage you need, or start from the power supply comparison hub.