How to install a power supply

When building your own PC, installing the power supply is usually one of the last steps. And perhaps as much as the motherboard installation, it’s the one that brings it all together, with power cables latching onto nearly every major component like braided black tendrils. For fun only, no horror.

Power supplies can still be a source of the latter if they fail or, worse, short out the more expensive parts of the build. Fortunately, the installation process is safer than it looks. Much like installing an SSD or installing a new CPU, it’s all about what plugs in where. Lots of “tab A goes in slot A”, rather than any serious electrical engineering.

This guide will walk you through the process and remember that installing a PSU is best done after all the other components – the motherboard, graphics cards, storage, etc. – are already in place.

Which power supply do I need?

More importantly, your power supply should match your case. Most conventional tower-style cases have room for standard ATX power supplies, while compact chassis designs can only fit an SFX-style PSU. Check your case specifications if you are unsure.

Then you’ll need enough watts to make sure the components doing the heaviest lifting are getting enough power – there’s no point investing in the best graphics cards or the best CPUs if they’re not getting enough power . For a very basic gaming PC, 450-500W will suffice, but I would recommend at least 650W for midrange builds. More advanced rigs, especially those with power-hungry GPUs like the RTX 3080 or RTX 3090, should go for at least 750W.

You will also see that the power supplies have ratings such as 80 Plus Bronze, 80 Plus Gold, and 80 Plus Platinum. These basically rate how efficiently a PSU can turn wall power into PC power. Higher ratings (Gold, Platinum and Titanium) are therefore better for your electric bill and should produce less heat, at the cost of being more expensive to purchase. Honestly, Bronze rated PSUs are fine for budget builds, but Gold is a better middle ground.

Finally, you can choose from modular, semi-modular and fixed power supplies. Modular models allow you to attach and detach each individual PSU cable from the PSU itself, so the only cables in the enclosure are the ones you need; Fixed power cables can’t be removed, so they’re cheaper, but can stuff your case with unnecessary wires. Semi-modular power supplies have both a few fixed cables and a few removable cable sockets. Personally, I prefer semi-modular power supplies when buying them for myself, since fixed cables are usually the most essential anyway.

A power supply fully installed inside a gaming PC.

How to install a power supply

Step 1: Start by making sure all the cables you need are connected to the power supply, especially if you have a modular or semi-modular unit. The essentials are the 24-pin motherboard power connector, an 8-pin CPU power connector, and as many GPU/PCIe connectors as your graphics card needs. You may also need one or more SATA power cables, for internal storage or to power some CPU coolers.

A modular PC power supply, out of its case, with several cables connected.

It is a modular power supply, with fully removable cables.

2nd step: With the PSU fan facing down, slide it into the case’s PSU bay. It’s usually on the back and in the bottom of the case, except for very cheap or older cases that have it on the top.

A power supply partially inserted into a PC's power supply bay.

The PSU fan should face directly into a vent, even if it appears upside down.

Some cases allow you to remove a plate from the back and then simply slide in the PSU, which can then be secured by reattaching the plate. On others, as you can see in these photos, the PSU goes in from the side and then bolts directly to the chassis. Either way, secure the PSU in place with the screws that came with the case.

A power supply being secured in position by tightening the PC mounting screws.

PSU screws should look slightly different from any other screws in your case’s accessory pack – they usually have hex heads.

Step 3: It’s cable connection time. There’s no particular order, but trying to avoid criss-crossing the cables will help you organize them later. Also, make sure to use all the routing holes around the motherboard tray.

The chunky 24-pin cable connects directly to the motherboard – it’s hard to miss, but it should almost always be on the right edge of the board – while the 8-pin CPU power cable plugs in top left of the mobo. Some high-end motherboards may have a secondary CPU power connector, but this is really only for extreme overclocking use, and your system will run fine if you only connect the primary connector. That said, graphics cards with multiple PSU slots will still need to populate them all.

A close up of CPU power connectors on the edge of a motherboard.

In this case (hahhhh) we only connect the main 8-pin CPU power connector on the right.

Also, don’t forget the SATA power connectors (the elongated “L” shaped ones). These can plug directly into SATA hard drives or SSDs; some CPU coolers will also have a SATA power connector, either as part of a hub or on a separate cable.

A PSU SATA power cable about to connect to an internal hard drive.

SATA power cables often have multiple identical connectors per cable, so you can use just one to power multiple drives.

Step 4: Tidy! You can usually place most of the cable next to the PSU, but cable ties or even straps built into the cases should be used to keep the rest of the cables tight and compact. It’s not just for aesthetics: a tidy case is easier to clean and easier to manage when you choose to change components in the future. Even if you eventually need to cut ties to access a particular PSU cable, it’s easier than untangling it from a mess of dusty spaghetti.

The interior of a gaming PC, before the cable management.


The interior of a gaming PC, after the cable management.

…and after.

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