How to install a power supply

Out with the old, in with the new PSU as we guide you through which one to choose for your PC case and how to install a power supply safely

Whether you’re building a gaming PC for the very first time, upgrading, or replacing parts, at some point you’ll need to know how to install a power supply unit (PSU). Don’t let the wiring get you down, though, as it can be a pain-free process. All you’ll need is a screwdriver, easy access to your PC case, and maybe a little patience when it comes to how you manage cables.

PSUs are often an afterthought or at the bottom of a wishlist thanks to their less than flashy nature, but they are the backbone of any gaming PC. Nvidia, AMD, and Intel all try to make their components as efficient as possible, but the best graphics card and best gaming CPU still need a healthy chonk of power to run properly.

If you don’t provide enough juice for your PC to function, that’s when you’ll experience crashes, BSODs, and dreaded short circuiting that risks your expensive parts – or worse. But don’t fret. Just follow our guide on how to install a PSU and you’ll be booted up in no time.

Picking the right power supply unit for your system is half the battle, and it’s much easier than you’d think.

1. Figure out what wattage capacity you need

Each of your components will come branded with the wattage they require on the back of their boxes. But these days most manufacturers offer their own power supply calculators to determine what capacity you will need, meaning you can go straight to the source if you plan to get a Cooler Master, be quiet!, Asus, Seasonic, or EVGA PSU. OuterVision’s calculator shines above the rest, however, with a basic option for beginners and more comprehensive breakdown for experts.

Even in its basic tab, OuterVision takes into account the make and model of your core components, while factoring in your RAM, storage, optical drives, monitors, and how long you use your PC for per day. The expert tab gives you finer control over things, however, taking into account clock speeds and cooling solutions. It’s best to add a few more additional devices even if you don’t use any, as this will give you some more headroom for future upgrades.

Remember to check your current PSU with any of these tools before jumping into another hefty purchase. You might just find that the power supply you have is up to the task after all. If so, fantastic! You don’t need to do a thing. But if not, the next thing to consider is the efficiency rating of the unit.

2. How efficient do you want to be?

The stickers you see on a PSU that claim it to be 80 Plus aren’t just for show. This means it converts the power from your wall socket into power for your PC more efficiently. Less wasted energy means less heat generated as a result.

Power Supply Load 20% 50% 100%
80 Plus 70% 70% 70%
80 Plus Bronze 80% 80% 80%
80 Plus Silver 82% 85% 82%
80 Plus Gold 85% 88% 85%
80 Plus Platinum 90% 92% 89%
80 Plus Titanium 90% 92% 94%

More recently, these categories have been expanded to include 80 Plus Bronze, Silver, Gold, Platinum, and Titanium ratings from least to most efficient. You won’t see Platinum or Titanium PSUs too often, as these are generally higher wattage power supply units that come at a premium price. Bronze, Silver, and Gold are a dime a dozen, however, making it difficult to recommend anything lower.

While not a direct measurement, these ratings are also a testament to a PSU’s reliability. Companies sometimes justify the bump in price with added quality assurance, meaning you’ll likely be able to squeeze more out of a premium model.

3. What is a modular power supply?

Standard PSUs come with all wires pre-built into the device. The problem here is that you rarely need to use all of them unless you’ve packed your system with multiple GPUs and a wealth of additions, condemning many of the wires to hang as an eyesore or live a life squished behind your motherboard.

Modular power supply units are more expensive, but allow you to choose which wires are in use and leave your system’s cable management looking like it belongs on a shop floor. You can even buy more cables from the manufacturer if you find yourself missing one for an especially hungry graphics card, for example. If this is too expensive, then you’re in luck, as there’s a middle ground.

Semi-modular PSUs, pictured above, bridge the gap between modular and standard models, with essential cables hardwired in and others left as optional. These are usually a little kinder to your bank account, too.

4. Find the right fit

The last thing to be mindful of when selecting the right PSU for you is its size compared to your case. Standard ATX power supplies are 100mm wide, but all vary in length. These won’t necessarily fit a Mini ITX or Micro ATX build that requires an 80mm wide fit, otherwise known as a Small Form Factor (SFX) PSU.

Make sure you choose the best PC case for your new build

At the other end of the scale, there are some bigger PSUs to be on the lookout for that would pose a challenge even in some full towers.

Power supply

5. Mounting the power supply unit into the case

After all that deliberation, you should now have a PSU that’s perfect for your needs and can seamlessly fit into your chassis.

If you are trying to upgrade or replace your power supply, you’ll first need to unhook all PSU wires from the motherboard and unscrew the old box from the case. You can leave your motherboard connected to the case and fans to save time, but if you find yourself lacking space to move around, you might want to unplug them and any other intrusive components to avoid unnecessary damage.

Depending on the type of power supply you’ve chosen, it’s preferable to plug in the cables you need before installing the PSU, as this can become difficult to reach later on. Slot the PSU into the case once everything is prepared, securing it with screws.

Learn how to overclock your CPU and GPU

Onto cable management, it’s best to feed the wires through the back of the chassis, behind the motherboard. Case designs vary but often come with their own cable management solutions, allowing you to pull each one through to the corresponding plug via the nearest hole.

Don’t forget to connect your CPU, GPU, Storage, and motherboard, as well as any other additions you might have. You can always consult your motherboard’s instruction manual if you find yourself stuck on what to plug where, but most motherboards now have a standardised layout if that document is long gone. And don’t worry, your PC won’t blow up as a result of a little mis-wiring, so don’t hold back.

If fitting the power supply was just the first step in building your PC, then you’re also going to need to know how to install a graphics card, perform a CPU upgrade, install an SSD, and maybe even optimise your system, giving you an fps boost. Don’t worry, we’ve got you covered on all fronts.