How do I know which power supply I need?

How do I know which power supply I need?

Not sure what power supply you need for your PC? Well, we are going to solve your doubt in this article, since we will give you the most important keys to know what features of a source depend on the equipment you have. In other words, we are going to teach you how to choose a source with the correct power, the necessary connectors, and appropriate to your needs.

Power is the need that varies the most depending on your PC

We start strong since we do it talking about the power, which is basically what depends the most on the components that you are going to put, particularly the graphics card and the CPU.

First of all, we want to make it clear to you that if you choose a model that does not lie in its specifications (some do so by taking advantage of misinformation, beware!) the source will be able to provide you with all the power it advertises. Advertised maximum power output is not dependent on efficiency or anything like that! More or less efficiency just means there will be more or less additional waste for the same power output.

In this regard, we are going to assume that a 550W source is usually more than enough for most configurations on the market. This, which may lead some to throw their hands in their heads, is an easy reality to verify simply with our graphics card analysis, where we leave consumption data for the complete equipment.

Another option is to use examples such as our power supply guide by price, where we have specific recommendations for different GPUs, thinking about what they need when accompanied by a mainstream processor. If you are going to put a very high performance CPU, perhaps you should consider increasing the values ​​that we put below by 50 or 100W.

We do not have all the GPUs on the market here, as there have been several releases in the meantime. Although we will update the guide soon, we leave you our comments on the new GPUs from NVIDIA and AMD:

NVIDIA RTX 3080 and 3090 graphics cards 

The new NVIDIA RTX 3080 and 3090 graphics cards have shaken the market for their consumption, breaking the trend of sources consuming less and less power. For this reason, it has become common to recommend 750W or even 850W sources for MonoGPU equipment, and we do so for RTX 3080 and RTX 3090. Not for any inferior graphics. We have an entire article dedicated to consuming these charts . For the 3070, 650W or 750W will be more than enough.

Regarding the AMD RX 6000, there is no detailed information about it yet, but we will boil down to AMD’s recommendations:

  1. 650W for the RX 6800
  2. 750W for the RX 6800 XT
  3. 850W para la RX 6900 XT

Number of connectors needed

Let’s go now with a point quite linked to power. You must ensure that the power supply has a sufficient number of connectors. On the one hand there is a connector that you will have yes or yes, the ATX, and the CPU. Some boards support 2 connectors, but unless you’re running a high-drain Threadripper or Intel X299 you really don’t need them. (1 8-pin CPU socket can handle up to ~380W on its own.)

The one that will undoubtedly be the determining component in this matter is the graphics card. Depending on what you have or plan to have in the future, you will need a specific number of PCI Express connectors. Here the same thing no longer happens with the ATX or the CPU, which are insured, but the source you buy could have 2, 4, 6, 8, 10… or none.

Well, it boils down to checking the number of connectors your graphics card has. You must look for the exact model that you are going to buy. If you are going to put an RX 580, for example, it is not worth looking at just anyone since some will have only 1 PCIe and others will have 2. Neither is it worth the assembler’s brand and that’s it, it has to be the complete model. For example:

  1. The Sapphire Radeon RX 580 Pulse has 1 PCIe connector.
  2. The Sapphire Radeon RX 680 Nitro has 2 PCIe connectors.

Only one word has changed! Once you know how many PCIe it has and how many pins there are (6 or 8), you should check if the source also has them.

You also have to keep in mind that, in certain cases, you have to assess not only the connectors but also how many PCIe cables there are. Let me explain: most power supplies do not have 1 PCIe connector for each cable, but rather 2. This division, which is done to save costs, does not cause problems with most graphics cards. But with the models that consume the most it can be a problem.

Think that you would be putting two PCI connectors but that in reality you have the same current limitation as if you had one (because of the cable band). With an RTX 3080, 3090, a Vega 64, etc, you will have to use 2 different PCIe cables.

Finally, we have the SATA and the Molex:

The installation of a SATA power cable

The amount of SATA depends on the number of disks you have, and all the auxiliary devices that need it. Here it is not only about the quantity, but about its distribution. Imagine that you have a single SATA cable with 3 connectors, and you are going to connect a disk and a liquid cooling that needs it. If they are too far apart, it won’t give you the cable. It’s that simple. In most cases, having 2 SATA strips is enough.

In the case of Molex, don’t worry, you probably won’t be using more than one (or none), so it’s not something we should care about.

Let’s not forget the format

Most PC configurations need a source with ATX format, that is, the standard and known to all. But in other cases, when it comes to ultra-compact PCs or those that are in some very special box, this format may not work.

For this reason, you should consult the power supply support of your box, unless it is a normal and current semi-tower or tower. If your PC has a small form factor, it is very possible that it only supports sources with formats such as SFX, SFX-L or TFX.

In this regard, we have an entire article dedicated to looking at the various form factors of a power supply. There you can find how to get what you need.

As a final point, it could be mentioned that the source supports the input voltage of your country. Today there are two types of power supplies:

“Full range” sources, which accept any input voltage. You should see, at some point, a marking similar to “100-240V”.

Sources 230V only. These only support voltages of 200-240V, used in Europe and some Latin American countries such as Chile, Argentina, Bolivia, Paraguay, or Uruguay. So be very careful if you are from a country whose input voltage is 115V, such as Mexico, Colombia, Venezuela, Ecuador or the US.

Many of you will also know those that had a switch to choose the voltage. Those are no longer around today, except for really bad and outdated models.

Choosing a quality source

Let’s go now with something that does not depend too much on the equipment you have, but not because it is not important, quite the opposite: it is essential that you buy a quality source! If you don’t make the right choice, you could run into problems, which could simply be the source being damaged, but it could also take some component away.

Also, our power guidelines only apply to models that meet a minimum of quality, and those will be the ones that will have no trouble delivering all the power they advertise. If we are talking about a bad source, then it surely has false specifications, and it is obvious that our power recommendations will no longer apply.

There are many ways to determine if a power supply is of quality, but this time we are going to recommend that you use our updated power supply guide , where we leave you very important guidelines to know as well as some tips. If you have questions about a specific model, we invite you to ask us in our hardware forum or in the comments box of this article.

Final words and conclusion on what power supply do I need

In this article we have broken down the most important keys to know which font you need based on the components of your PC.

Within this issue, what has undoubtedly been more important is the power of the source and its number of connectors.

For the first, it is essential that you make a choice adjusted to the needs of your PC, neither oversize nor fall short. Starting from the basis that 550W of quality is more than enough for any mid-range PC, we must take into account all those components that can raise the requirement, mostly a very demanding CPU such as an i9-10900K or a super powerful GPU such as an RTX 3080 or an RX 6800 XT .