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Get the Most Power From Your PC: A Guide to Computer Power Supply Units

Introduction to Computer Power Supply Units

Computer power supply units (PSUs) play an important role in the building and operation of any computer system. They act as the primary source of electrical power for a system, providing the necessary power for components like the motherboard, processor, memory, storage drives, and peripherals. Without a PSU, a system simply won’t work.

A PSU comes in various shapes and sizes, and there are several types of power supplies available on the market. Each type of power supply serves a different purpose and the type of PSU you choose will depend largely on the size of your system and what components you plan to install. This guide will explain the different types of PSUs, how to size them correctly, their connections, installation instructions, basic troubleshooting technique and more.

Types of Computer Power Supply Units

Choosing a power supply unit (PSU) for your computer can be overwhelming, as there are several types to choose from. Different types of PSU offer different advantages and disadvantages that will depend on the purpose and system of your computer. In this section, we’ll look at the main types of PSU, and discuss their benefits and drawbacks.

  • ATX – ATX is the most widely used and accepted type of power supply in the PC industry, and is the standard type used in consumer-grade computers. This type of PSU offers a great balance between quality, performance, and cost.
  • SFX – SFX is a smaller form factor than ATX, which makes it more suitable for tight spaces or small form factor builds. Although less powerful than ATX, it still provides enough wattage for a decent gaming PC, and is more energy efficient.
  • Modular – Modular PSUs have become increasingly popular due to their neat wiring and improved cable management. Cables are only connected when necessary, reducing the amount of clutter in the case. These PSUs are also more energy efficient than older models.
  • Non-Modular – Non-modular PSUs are cheaper than modular ones, but can lead to more cable clutter in the case, and they are generally less efficient.

Each type of power supply has its own set of advantages and drawbacks, depending on the specific needs of the user. It is important to know what type of PSU works best for your system in order to get the most out of your money. For example, if you are building a gaming PC with a small form factor, then an SFX PSU would be a better choice than an ATX PSU.

Sizing Guide

When it comes to selecting a power supply for your computer, the most important factor is picking one that is properly sized for your system. The size of a power supply is determined by the wattage rating listed on the unit. That wattage rating is also sometimes called the power draw, or power output, of the unit.

The power requirements of your system are determined by the components you choose, including the type and number of internal components as well as any external peripherals. Every PC component has an associated power draw, and these need to be added together to determine the total power draw for the system. Once this is determined, you can select a power supply with a wattage rating just above the total power draw of the system.

It is important to note that not all power supplies are created equal. Some units are more efficient than others, meaning they require lower wattages to reach the same total power draw of your system. This efficiency rating should always be taken into account when selecting your power supply.

The size of a power supply also determines the number and type of connectors available on the unit. Most computer power supply units will feature four or five main power connectors as well as a variety of additional connectors for devices. Depending on the size of your power supply, you may have more or fewer connectors than necessary to connect all of your components.

When sizing a power supply for your computer, it is important to consider both the wattage of the unit and the types of connectors available on the unit. A unit that is too large may be overkill for your system, while one that is too small may not be able to power all of your components. Properly sizing your power supply will ensure that your computer always has the power it needs to run smoothly.


When setting up a computer system, it is important to understand the different types of connections required between the power supply unit (PSU) and the rest of the system. To ensure that your system runs as efficiently as possible, you’ll need to know which types of connections are best suited for your particular needs.

The main type of connection used for a PSU is a 20- or 24-pin connector. This connects the PSU to the motherboard, and is typically located at the back end of the PSU. Other connections include 4-pin Molex connectors, which connect components such as hard drives and optical drives to the PSU, and SATA connectors, which are used to connect newer components such as SSDs and HDDs. In addition to these connections, some PSUs also feature PCIe connectors, which provide dedicated power to graphics cards.

It is important to ensure that the PSU you select has the necessary connections to accommodate all of your system’s components. Otherwise, you may find yourself having to use adapters or other workarounds in order to connect your components to the PSU.

When selecting your PSU, it is also important to consider the wattage of the unit, as this will determine how many components the PSU can handle. Generally speaking, the higher the wattage, the more components the PSU can handle.

Installing a Computer Power Supply Unit

Installing a computer power supply unit is an important part of any computer build. Ensuring that it is set up properly and securely will provide the stability and performance required for reliable operation of your computer system. Follow this step-by-step guide to ensure the best results.

  • Step 1: Acquire the necessary components. You will need the PSU, screws, and other mounting hardware specific to your computer case.
  • Step 2: Identify the power slot in your computer case. It will typically be at the back of the case near the top.
  • Step 3: Secure the power supply unit to your computer case with the provided screws. Make sure that all four corners are securely fastened in order to prevent the PSU from slipping or vibrating during operation.
  • Step 4: Plug in the power cables to the motherboard and all other components requiring power. Start with the 24-pin ATX cable, then plug in the remaining connectors, such as SATA and PCI-E cables.
  • Step 5: Connect the power cord from the power supply into a wall outlet or power strip. Make sure that the outlet is rated for the amount of power the PSU is drawing.
  • Step 6: Test the power supply before booting your computer. Flip the power switch on the back of the power supply and make sure that the fan starts spinning. If not, you may need to reset the power supply or replace it.

Once the installation is complete, your computer should be ready to start up. Make sure that all connections are secure before powering on your computer for the first time after installation.


When things don’t work right with your computer power supply unit, it’s important to take the correct steps to diagnose and fix the problem. The first step is to make sure that the power supply is firmly plugged into a working outlet – check the circuit breaker if there is an issue with the wall connection. Once you’ve made sure that the power supply is getting power, check the fan speed on the power supply. If the fan is not moving at all, then there could be an issue with the internal components of the power supply. If the fan is running too quickly, it might indicate that it is overheating.

It’s important to check the connections between the power supply unit and other hardware components in the computer. If any of the connections are loose or disconnected, then this could be the cause of the problem. Make sure that the power supply cables are firmly connected to the motherboard, as well as other components like the CPU. Also, be sure to check the power switch on the power supply and make sure that it is set to the ‘ON’ position.

If these troubleshooting steps do not help to resolve the issue, then it could be indicative of a more serious problem with the power supply itself. In this case, you may need to contact an expert technician who can help to diagnose and repair the issue. Alternatively, you could replace the power supply with a new one.


This guide has provided an overview of the basics of computer power supply units, including types, sizing, connections, installation and troubleshooting. Now that readers understand the ins and outs of computer power supplies, they can make an informed decision when selecting one for their build.

Computer power supplies are an important part of any PC build, and having a reliable one is key to a successful system. Knowing the basics of PSU selection and installation will help ensure that readers have a stable and reliable computer experience.

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