Should you install your PSU facing up or down?

Deciding on whether to mount your PSU either facing up or down depends entirely on a few factors, namely case design, airflow with other fans, and the power supply unit itself. The answer is an easy one, should you have enough room between the intake and the floor (and your case has a grill on the bottom for a PSU fan to draw air) you'll want to have your PSU facing downwards.


This will aid in the unit drawing in much-needed cool air when under load. Granted, a PSU will rarely be under much stress in everyday use — in fact, many units today have an ECO mode that disables the fan unless temperatures and load hit certain levels — but it's best practice to aim for optimal performance. That said, if you want to install your PSU facing up, that's perfectly fine too.

Why is it important to have the PSU facing a cold air intake, if your case has one available?

It's all about maximizing available cool air and not having to rely on keeping the inside of the case lower to account for more components to cool. With the PSU taking in its own supply and exhausting it out the rear of the case, it creates a separate system that's not critical for operation but ideal to prolong the life of the unit.

Core P5 PSU

Core P5

Should you own carpeted flooring, it's not the end of the world, but this does hold the potential to cause issues when you've failed to sit the case on an elevated surface. Invest in a dust filter if one is not already attached to the grill for the PSU and pick up a small piece of wood or other material to sit the computer on. This should help reduce the risk of suffocating the unit or worse, ingesting extra fluff.

There's just one thing to note when it comes to your PSU and installing it inside a chassis. Never have the fan facing a plate of metal. Should the PSU intake be facing towards the case itself with little room to suck in cold air, you're likely going to have a bad time down the line. And the last thing you want to do is replace the PSU.

Best Power Supplies for your PC

Rich Edmonds
Senior Editor, PC Build

Rich Edmonds was formerly a Senior Editor of PC hardware at Windows Central, covering everything related to PC components and NAS. He's been involved in technology for more than a decade and knows a thing or two about the magic inside a PC chassis. You can follow him on Twitter at @RichEdmonds.

  • I've never seen my PSU fan spin. It's a RM450. Powering an i5-6500 and 1060(3G)
  • Ditto. I've got an RM850X running a 4690K and an RX480... I may never have the fan spin lol.
  • Bottom and face up only (no, it's not a sex position): it takes less heat and less dust. The fan noise, when running, is also weakened by being inside the case.
  • not the best solution because hot air from the whole PC will be sucked into the PSU. The best possible solution is to install the PSU on the bottom with an open window + dust filter
  • Warm air goes up, inside the case it is the coolest position, for a RM850x it's not a big deal. (well it's not a big deal for most PSU at all). Dust filters only stop macro-dust agglomarates and hairs.
  • Yeah, I can see the logic in having the PSU draw from outside the case, especially in a smaller rig. But personally I'm still using my old Antec 900, so not only does it not have an external PSU grill but there's never any warm air inside the case anyway!
  • Warm air will warm the entire box making it warmer than the outside air. It's not an issue with my case because it's a LAN box I've converted for PC use and so the power supply is separated from all the heat generating components. But in standard cases, the power supply will still be sucking in warm air if you have it pulling from inside the case. It doesn't matter either way, but it is still pulling warm air even if it is on the bottom.
  • That's precisely what the PSU intake fan is designed to do. Take in the warm air from the case and expel it out the back. It's not just to cool the PSU itself. If you have other fans in the case, then you may not neeed the PSU to do also aid in airflow of the main part of the case, but that is an "advanced" configuration that should not be recommended to novice PC builders.
  • If I install mine fan down, there will be no air flow since the p/s is on the bottom in my case.
  • What exactly do you think a PSU is?
  • Had the same issue with my last 2 builds due to case design. I'm actually OK with it due to the fact that on these last 2 builds the case had at least 5 places to mount fans and most were already populated.
  • How many places to mount the PSU?
  • Usually, when a case has its PSU located at the bottom there will also be vents under the case that will allow the PSU air to draw air from the bottom.  The case should also have rubber feet of some kind to lift it off the ground.  This is how all of the computer cases that I have worked with are designed.
  • Is there any good passive PSU?
  • You mean a fanless one?  I don't know of any.  If you ever put any serious load on your machine, you probably don't want to take the chance on a passive PSU.  Unless, of course, you already have plenty of other fans in the unit and your room is kept cool all the time.  The bottom line is that the cooler you can keep things the longer the hardware will survive.
  • I'm not talking about a heavy gaming or workstation PC. I know that there were some passive PSUs ten years ago but I haven't seen any new.
  • This PSU from Seasonic  $136 from Amazon. I normanly use the non-Passive Seasonic PSU. My current Pc i5 4690k @ 4.3 GHz, GTX 980 Ti, and even with playing 4k games The Witcher 3 and similar type games the Seasonic 650w 80+Platinum the fan very, very rarely runs.
  • Yep. I have the 520, i7 and GTX 1080 and zero issues.
  • My PSU is 8 years old. Just like GPU. And it's pretty loud. Didn't knew that newer PSUs are quiet. Good to know. Thanks.
  • I personally use the Antec TruePower Classic 750 watt PSU and it's pretty quiet even though the fan spins usually. I've heard that Corsair makes some pretty good modular and semi-modular ones but I can't comment on their noise output since I've never used them.
  • A lot of good PSU's operate without the fan... but it's wise to have one if things warm up (you really don't want a meltdown there). I have a Corsair AX1200i and the fan has never turned on in the 6 months I've owned it... and the max temp ever reached is 38 C. But it was kinda overkill for my system so the load is kept quite low.
  • I have a Seasonic platinum 520w as I recall (I'm not at home). It is fanless and never had a problem. I have an i7 3770k stock and a GTX 1080 stock and no issues. If I were to overclock maybe. I chose that PSU for silence as the rest of the rig is very quiet with some very low noise fans moving the air. The case is also an OTC form factor.
  • As others have mentioned, the Seasonic fanless PSU's are a very good choice.  Seasonic also has another type of PSU that has "hybrid fan" operation.  I've been using one for the past 5 years.  Basically it runs in fanless operation until it gets to a threshold then turns on the fan when needed.
  • Depending on your needs, many small form-factor PCs (like mini-itx and the intel NUC) can use external brick-style power supplies, which are often fanless.
  • My PSU is an old thermaltake, the fan is on all the time as far as I know.  it is facing down at the bottom of the cfase, drawing air in from below, but the case is on a stand, so is a good distance off the floor. I did check the dust filter a few weeks ago, it was ok really to be honest, since the machine have not been moved for nearly a year.  
  • I found this to be a really weirdly/poorly written article. Up/Down is entirely dependent on the design of the case and positioning of the power supply within it. Most consumer cases I've seen still have the power supply positioned at the traditional top of the case, so the info in this article is wrong for them. The "real" question is "should the power supply's intake fan be positioned towards the motherboard (to draw in the hot air from the CPU & other components) or towards the end of the case? (to draw in fresh air)" Not all cases have an intake grille in the right spot, so if there's no intake grille to draw in fresh air, then the power supply has to be mounted to draw in air from the case insides. The article gets this right, but phrases it in a way that would be confusing to most users.
    If the rest of the case has sufficient fans, then making the power supply take in fresh air can have cooling benefits, but only if you know what you are doing. However, most cases ship with very few fans, if any, and so in most stock situations, the power supply _has_ to be pointed to draw air in from the motherboard area in order to expel it out the back of the case, otherwise that hot air from the CPU, GPU, etc. has nowhere to go.
    If you don't know 100% that it can work the other way, point the intake fan towards the motherboard. That's how it was designed t be used, and how PCs have been done for decades. If you really know what you are doing, then you can point the power supply in the other direction.