by If you’re building your own gaming PC, you may have wondered what type of power supply unit (PSU) you need.
Depending on the system you’re building and the components you’re including, there are some complexities around things like the power needed and even the cables required.
We’re here to help you with an explanation of everything you need to know before you start. Getting this right is important as the power supply is the beating heart of your computer and failure can be catastrophic. Don’t worry though as things will become clear soon.
How much power do you need?
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A common problem people encounter when building a PC is calculating how much power they need. Power supplies are sold based on the wattage they can deliver. The more components you use, the more power you need to power your system.
If you’re running high-end components like the latest CPUs and graphics cards, you probably need even more performance than a lower-budget or mid-range device.
So you might just think that buying the biggest PSU is the best course of action, but that’s not always the case as it’s wasteful in terms of both money spent and power consumption. In addition, there may also be problems with the case you have chosen.
On the other hand, it might also be tempting to save money by buying a cheaper power supply. Saving can also be an issue as a poor quality power supply can potentially short out, overload, or just plain wreck your entire PC.
So how do you know which power supply to buy?
Start by calculating the wattage
The easiest thing to do first is to figure out how many watts you need to adequately power your PC. It’s actually easier than you might think.
There’s a handy PSU calculator that you can use to work out how many watts you need based on the components you’re using.
Use this tool by simply typing in all the different components that you will include in your build. We recommend doing this before you even start buying parts so you can figure out what you need in advance. If you have a shopping list of parts in mind, this tool is ideal for identifying your needs.
It’s also useful to ensure that you don’t buy a power supply that doesn’t meet the needs of your system, thereby avoiding problems that might otherwise arise if you buy based on price alone.
Go through the tool and fill in all the things you need and then see what it recommends.
What about your case?
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Some cases require a different type of power supply. You will find that small form factor cases often require a matching small form factor power supply.
You may find that Mini-ITX, Micro-ATX, and even some mid-tower ATX cases require a smaller power supply. It’s important to check the specs of your case before purchasing it or the power supply you need to power your computer to ensure the two will work seamlessly together.
Some smaller cases will require an SFX power supply as they are smaller and don’t take up as much space but can still provide enough power for your system. However, it’s worth noting that it’s not often that you can get a high-wattage power supply in a small form factor design. So don’t expect to fit a high-end gaming system into a tiny chassis.
Likewise, the larger power supplies, 1,000 watts and above, are often larger and may not fit all cases. Even some mid-tower cases might struggle with some of the larger PSUs. Therefore, it’s important to check the specs of your preferred case before committing to the different parts.
Nvidia GeForce RTX 40 series requirements
With the introduction of Nvidia’s RTX 40 series graphics cards came a new set of performance requirements that may seem complex at first.
The good news, however, is that you don’t have to worry for the most part when shopping for the latest graphics cards from Nvidia. Older PSUs will continue to work with the RTX 40 series GPUs provided they have enough wattage to meet the recommendations.
However, there are a few things to consider:
- The Nvidia GeForce RTX 4090 requires 450 watts of TGP (total graphics power), which means you’ll need at least an 850 watt power supply (more if you have a lot of components).
- The Nvidia GeForce RTX 4080 requires 320 watt TGP, which means you need a PSU with at least 750 watts
Not only do these new graphics cards use more power, they also require slightly different power connections on your power supply.
Each new GPU comes with a new adapter that allows you to connect to your current power supply using existing 8-pin PCIe connectors.
The reason for this is that Nvidia is introducing the new PCIe 5.0 power connector (12VHPWR) for its GPUs. In the future, this means you can purchase an ATX 3.0 power supply. This one features a dedicated PCIe Gen 5 connection, so you can get a single cable to connect from the PSU to the GPU.
MSI is one of the first companies to introduce one of these PCIe Gen 5 compatible power supplies, but they’re not commonplace just yet.
Meanwhile, the standard adapter is a bit messy as it requires three or four 8-pin PCIe power cables to connect the power supply to the adapter and then to the graphics card.
Nvidia has an explanation that goes a bit in-depth here, as well as this handy chart:
Nvidia also says that:
“PSUs typically only provide up to 2 x 8-pin PCIe connectors per output cable. RTX 4090 and RTX 4080 16GB require at least 3 x 8-pin PCIe connectors or a 450W or larger PCIe Gen 5 connector.”
Alternate cables
If you don’t like the look of the official Nvidia adapters, there are a few alternatives. Corsair has a 600W PCIe 5.0 12V HPWR Type 4 PSU power cord that can be used instead. This is designed to work with all Corsair Type 4 power supplies and give you a much easier connection to Nvidia RTX 40 series graphics cards.
If you’re not sure, Corsair also has a compatibility chart so you can check that your chosen cables and power supply will work well together.
