Which power supply do I need? – Complete Guide

When it comes to choosing a power supply for your computer, it can be a daunting task. With so many different types and sizes of power supplies available, it can be difficult to know which one is right for your system. In this article, we will discuss how many watts do I need?.

How many watts do I need?

This question is asked by everyone who wants to assemble their own PC or is looking for a replacement power supply. However, there is no general answer to this question. Of course, this depends on the type and number of components installed.

A high-end gaming PC requires significantly more power than a normal, simple office PC. Many tend to reach for unnecessarily “large” power supplies without thinking twice. The superstition that a power supply draws as much power as it can deliver power is definitely wrong.

A power supply basically draws as much current as it needs. You should make sure that the consumption of the power supply is in the range between 20% and 80% utilization of the total capacity since this is where the efficiency is highest.

But more on that later. A power supply unit with a maximum of 250-300 watts is sufficient for an office PC without a dedicated graphics card. A multimedia PC with a dedicated graphics card, which is not designed for games, needs about 300 watts. Gaming PCs require the most performance.

When using several graphics cards (SLI or Crossfire systems) at the same time, you can quickly reach 1000 watts. The stated consumption values are for guidance only and cannot be taken as a general rule for PCs in this category.

Straight to the recommendations Here is a small table that roughly shows the consumption of the most important components (under full load!) in the PC: To determine the required power supply, you can also use various power supply calculators, such as the power supply calculator from be quiet, online.

If you also want to overclock, the power consumption of the CPU and GPU can quickly increase. For this purpose, you should plan a corresponding reserver for the power supply unit.

Energy efficiency: save on electricity and not on quality

PC power supplies offer more and more features and, above all, power-saving technologies. The 80Plus seal of approval should be mentioned here as a well-known certificate. It describes the efficiency of the power supplies.

Starting with 80Plus for PSUs with 80% efficiency (at 50% load and measured at 115 VAC), through 80Plus Bronze with 85%, 80Plus Silver with 88%, 80Plus Gold with 90%, 80Plus Platinum with 92%, to the latest seal, the 80Plus Titanium with 94% efficiency.

Source: PLUG LOAD solution Let’s look at a small example at this point: Since the voltage of the socket is 230V, the power pack has to convert the voltage into 12V and 5V rails. The conversion does not work lossless.

This means that a little more power is drawn from the socket than is actually necessary for the PC. Our PC should now be an average gaming PC with the following equipment: an Intel i5 with a boxed cooler, 8GB RAM (2 modules), a hard drive, an SSD, a DVD drive, a mainboard, a power supply, and a powerful gaming graphics card.

So if we take the consumption values from the table above, we get 369 watts under full load. Even if the PC only rarely reaches this maximum, let’s keep counting on it. In general, you should be well served with a 450-500 watt power supply.

However, let’s now differentiate between different efficiencies: With a component consumption of 369 watts, an 80Plus power supply unit draws a total of 461 watts from the socket, an 80Plus Bronze power supply unit 434 watts, an 80Plus Silver power supply unit 420 watts, and an 80Plus Gold power supply unit draws 410 watts, an 80Plus Platinum PSU 401 watts and an 80Plus Titanium PSU 393 watts.

If we convert this to annual consumption for eight hours a day, we arrive at the following values: The table shows that the annual price differences are not as large as one might have expected. It should be noted that our calculation is based on the fact that the PC is operated under full load for eight hours every day of the year.

It really makes no sense to buy an 80Plus power supply or even worse. Here you should start looking for 80Plus Bronze or 85% efficiency. Good power supplies are available here for as little as €35.

But even expensive 80Plus Titanium power supplies only pay off after years of use. You are best served with 80Plus Bronze to 80Plus Gold models.

Connections: Where is all this going?

Of course, the connections provided are also very important for choosing the right power supply unit. Does the power supply have the required number of SATA power connectors? Do I still need 4-pin mole plugs? Does my graphics card need a separate power connector, or even two?

So let’s first introduce the different power plugs: The 20 + 4 pin ATX connector is responsible for the mainboard’s power supply. This connection is part of the basic equipment of every power supply unit. The 4 + 4 ATX/EPS connector is also available with every Netzteil at least in a simple version and supplies the CPU with power.

SATA cables ensure the power supply for all drives and hard disks in the PC. The number of available plugs varies depending on the power supply manufacturer and the product. The 4-pin Molex connector used to be used as a power connection for drives. 

But today it is mostly only required for fans or other additional components. The PCI-Express power connector, PCIe connector for short, supplies the graphics card with power.

Particularly powerful cards even need two connections with the additional 2-pin connector (6+2pin). Therefore, you should also make sure that the power supply provides the appropriate connections.

Many power supplies offer the “cable management” feature. Sounds a bit strange at first glance, but it makes perfect sense. Power supplies with cable management only have the obligatory cables for connecting to the mainboard permanently installed.

Any additional cables required are then additionally connected as required. This saves space in the case and also a lot of time that you would otherwise need to store the remaining cables neatly in the case. Of course, this feature also costs a little more.

But if you like things tidy on your PC, you should consider a power supply unit with cable management. In most cases, power supplies in the higher price segment offer significantly more connections than cheaper products. It also applies: the more watts a power supply offers, the more connections are available.

After all, what’s the use of a 600-watt power supply with only one plug each? In our price comparison, you can also conveniently filter according to the desired number of plugs.

Purchase recommendation: Watt now?

As already mentioned, the power supply is actually the most important part of the PC. The entire power supply runs through it. Consequently, it is immensely important that the individual components are supplied with sufficient and, above all, stable power.

Inexpensive power supplies in particular have problems keeping the voltages stable over a longer period of time. In the worst case, the result would be a defect in the PC, and in the best case, a computer that regularly crashes. The processing also usually falls by the wayside with supposedly cheap power supplies.

In many cases, inferior (cheap) components are used here. Inexpensive power supplies also come up with only very sparse equipment and can drive the buyer to despair with loud fans or cables that are too short. Cheap power supplies often cannot even deliver the performance for which they are declared, as this test shows.

In order to prevent this from happening in the first place, you should rely on a good quality power supply from the outset. And a good power supply definitely does not have to be expensive. Starting at €35 up to well over a hundred euros, the range of good power supplies is huge and confusing. Here are our recommendations for three example systems:

Office PC

Such a PC is used for office work and the Internet. The requirements for the power supply are in particular stability, low volume, and endurance. Be Quiet! 450W be quiet! System Power 10 ATX 2.52 power supply, (BN326) 2 more prices and providers Be-Quiet! PURE POWER 11 400W (BN292) Best offer of:71.98€incl.

Shipping 7 more prizes and providers Seasonic CORE GC Series 500W (SSR-500LC) 1 more prize The small Be-Quiet System Power 10 is extremely inexpensive, offers good efficiency with 80Plus Bronze, and is sufficiently dimensioned for most office computers with 450 watts. If you need a little more efficiency, the 400-watt Pure Power 11 from Be-Quiet with 80Plus Gold certification is the best choice.

Seasonic, also a well-known power supply manufacturer, has launched the new Core series of cost-effective and energy-saving power supplies with an 80Plus Gold certificate. Reason enough to include the 500 models in our recommendations. Can’t find the right power supply? All power supplies up to 450 watts

Multimedia PC

We call a multimedia PC a PC that is mainly used for watching movies and listening to music. But also one or the other small game should be playable with it. Be Quiet! SYSTEM POWER 9 400W CM (BN300) Best offer of:49.49€incl. Shipping 34 other prices and providers Seasonic G12 GC series 550W (G12-GC-550) Best offer from: 69.85 € incl.

Shipping 8 other prices and providers Seasonic FOCUS GX 550W 80-Plus Gold (FOCUS-GX-550) Best offer from:93.85€incl. Shipping 17 more prices and providers The System Power 9 from be quiet is ideal for a small budget without having to forego good quality and equipment.

The Seasonic G12 550 with 80 Plus Gold is very reliable, energy-saving, and inexpensive. Seasonic’s Focus Plus GX 550 W also has 80Plus Gold, on customers always give positive reviews in tests, is modular and also very good in terms of value for money thanks to DC-DC technology. All power supplies up to 550 watts

Gaming PC

We call a gaming PC a PC that is designed to display current games smoothly. Can’t find the right power supply? All power supplies from 500 watts

Power supplies with 16-pin PCIe power connector

With the new Nvidia RTX 4000 series graphics cards, a new standard for graphics card power connectors has been introduced. The 12+4 or 16-pin PCIe 5.0 connector, also known as 12V HPWR, can carry significantly more power to the graphics card than the conventional 6+2 or 8-pin power connector.

In most cases, a single 16-pin power connector is sufficient to operate the new high-end graphics cards from Nvidia. All power supplies with 16-pin PCIe power connector

SFX format

More and more cases, mainly compact mini-ITX towers, only offer space for a power supply unit in SFX format due to the limited space available. All SFX power supplies in price comparison


In summary, it can be said that THE power supply does not exist. You look for the power supply according to the area of application, connections, and desired efficiency. Certificates like 80Plus Titanium sound great, but only pay off after several years of use.

If you buy one for the sake of the environment, you get the highest quality at a premium price. However, as our calculations show, power supply units with 80Plus Bronze and 80Plus Gold are optimal and therefore particularly recommended when it comes to the best price-performance ratio.

The relationship between efficiency, costs, and equipment is right here. What do you think: do you prefer to save on the power supply or on the energy? And how far do you go for the sake of the environment: does 80Plus Titanium justify the extra charge?

Leave a Reply