PSU fan direction doesn’t really matter. Your internal components will run at similar temperatures no matter where you point your power supply unit’s fan. However, having the fan facing downward is optimal as it reduces PSU temperatures slightly.
Keeping heat-generating components cool is one of the core tenets of PC airflow. However, many of us tend to forget the power supply unit (or PSU). The PSU is a heat-generating component like your CPU and GPU, but does it matter whether you orient your PSU fan up or down? Well, that’s what we’re here to find out.
Does PSU Fan Direction Matter?
Generally speaking, PSU fan direction doesn’t matter, although a fan-down (i.e., drawing air from outside) orientation is optimal.
Linus Tech Tips tested both orientations and found the only noticeable difference was in PSU temperature. Pointing the fan downwards (in other words, allowing the PSU to draw in cool air from outside) dropped temperatures four degrees down to 35 degrees Celsius vs. 39 degrees with the fan pointing up.
However, other components ran at the same temperatures regardless of whether the PSU drew air from in or outside the case. In this situation—a case without a PSU shroud and a standard blower-style GPU cooler—the power supply fan direction doesn’t matter. While some PC builders advocate having the PSU fan facing up so it functions as an exhaust fan to “suck hot air from the inside of the case,” real-world testing doesn’t bear this idea out.
Having the fan pointed downward and working as an intake fan drops PSU temps noticeably, so it’s the orientation we recommend. But the differences are small enough that we’re confident you’ll be fine either way. Thirty-nine degrees, for example, is still well within the safe zone for even a lower-quality budget PSU, so there isn’t much to worry about here.
Overall, your PSU’s fan direction won’t change too much as far as temperatures go, especially not for your main heat-generating components like the CPU and graphics card. But let’s look a bit more at both orientations, discussing why you may want to go with one or the other.
Why Point the PSU Fan Down?
Almost all modern PC cases will have ventilation holes in the bottom of the case, explicitly designed to let your PSU draw in cool air from outside. If your case has these, you should take advantage of them and orient your fan downwards for optimal temperatures.
Of course, as we’ve shown earlier, the difference between fan-up and fan-down orientations isn’t huge. You’ll be lucky to see more than a five-degree Celsius difference between the two. While that isn’t a lot, especially not for a PSU, we believe it’s always optimal to keep temps as low as possible for component longevity.
So if you don’t have any pressing need to orient the fan upwards, you might as well have the PSU fan facing donward to draw cool air in through the bottom of the case and keep your PSU cool.
Most modern PC cases will come with dust filters for the bottom intakes, so you won’t have to worry too much about the intake fan pulling dust into your PSU. Sure, you’ll have to clean the filter regularly to ensure it doesn’t get too clogged up, but that’ll only add a minute or so to your cleaning routine.
If you’re running a case with a PSU shroud, note that you may be forced to install the PSU pointing downward. Many older computer cases have solid shrouds with no ventilation grilles above the PSU area. These will obviously block the fan, which is the only situation where you must not install your PSU facing up.
Thankfully, many modern computer cases (like the Fractal Pop Air) now have ventilated PSU shrouds that let you install your PSU pointing up. Which brings us nicely to why you’d want to do that, which we’ll discuss in the next section.
Why Point the PSU Fan Up?
If you’re worried about PSU temperature and longevity, you’ll want to install your PSU facing down. The differences will be minor, yes, but every little bit counts for a component’s longevity. However, there are some situations where you may want to flip it and have it pull hot air from inside your case.
The main reason to flip your PSU is if your PC is sitting on a thick carpet that can potentially block your case’s bottom intakes, depriving your PSU of fresh air. While we recommend avoiding carpets wherever possible, we understand that that’s not always possible. So if you have to keep it on the carpet (and don’t want to place your PC on a PC stand), installing your fan upwards is vital to ensure it doesn’t overheat.
You’ll also want to point your power supply unit upwards if you’re using an older case that doesn’t have vents at the bottom of the case. These are becoming increasingly rare (if not nonexistent), but it’s worth pointing out in case you happen to be using one. If you don’t have bottom vents, point the PSU up.
You may also encounter the odd PSU with labels that only look right with the PSU installed facing up. However, most PSUs accommodate both orientations by having one label oriented for fan-up installations and another for fan-down installations.
Corsair, for example, does this for all its PSUs (including the RM850x, one of our favorite 850-watt power supplies). You get one sticker that looks right when you install it with the fan up, and the other sticker looks right when you install it with the fan down. So it’ll look right no matter your favored orientation.
However, as we pointed out earlier, there’s no performance- or temperature-related reason to have the PSU fan facing upward. Your other fans should be able to handle the job of sucking hot air out of your case without needing your PSU to do some of the work.
What About Top-Mounted PSUs?
We’ve focused on bottom-mounted PSUs, as the vast majority of modern PC cases have a PSU chamber in the bottom. However, there are always exceptions, like the Fractal Torrent and its top-mounted PSU. While it’s currently the only big-name PC case that does this (to our knowledge), we wouldn’t be surprised if other manufacturers follow suit due to how well it worked in the Torrent.
For a top-mounted PSU, simply reverse the directions we discussed earlier. In other words, point your PSU fan up to draw air from outside or down to pull air from inside the case. In the Torrent’s case, you have to point the fan downwards and have it work as an exhaust fan, as the top panel doesn’t have any ventilation. Sucking hot air into your PSU isn’t ideal for PSU temps, but it’s fine and won’t wreck your PSU.
So there you have it: PSU fan direction doesn’t matter hugely in a conventional case. Component temperatures are similar (if not identical) between the two orientations, with only a minor PSU temperature delta separating fan-up and fan-down setups.
If you want to keep PSU temps as low as possible, have your PSU draw air in from the outside (in other words, pointing downwards for a bottom-mounted PSU). But there’s no harm in pointing it upward, either. But not every airflow decision is this inconsequential; head over to our PC airflow guide for tips on keeping your CPU and GPU cool.