What is a PSU

A PSU is a Power Supply Unit and is one of the most important components within a computer. It converts alternating current from the outlet supply into a direct current that can be used to power all the internal components. The PSU is mounted inside the back of the case and has a fan opening at the back which sends air out of the computer case. This fan is the only part of the PSU that you actually see when it is in the case.


Why do you need a PSU?

To put it bluntly, without a PSU, the internal components of your computer will not work. Therefore, for the computer to run, you need a PSU. Simple.


Choosing the right PSU for your system

The PSU is one of the most important components in the computer system, as it supplies power to all other components. Therefore, it is incredibly important that you choose the right one. Selecting the right PSU can be tricky, as there are lots of factors to consider and choosing the wrong one could cause compatibility issues.


PSU’s come in different sizes called form factors. There are a range of standard sizes, but even these can differ in lengths. It’s important to know which size fits the inside of your computer. If you choose a PSU of the wrong size, it simply won’t fit in the casing of your computer. It’s as simple as that!


Before you buy a PSU, you need to know the wattage of the power supply that you are going to need. To know this, you will need to know the power consumption of all the different hardware components within your computer. To a novice, this might sound complicated. However, there are ways you can do this which make it easy. The main way is by using an online power supply calculator.

This is an important step. If you choose a power supply which has too much power for your components, this could mean you are spending more of your budget on the power supply than is necessary. However, if you choose one that has too little power, it can cause instability issues.

A tip would be to get a PSU that has a slightly higher wattage than you think you might require. This reduces the chance of it being under powered.

PCle connectors

If you have or are planning to get a mid-range to high-range graphics card, make sure the power supply you get comes with at least one 8-pin PCle connector. If the power supply you require for your system is 500W or higher, then it is advised that you get a power supply with 2 8-pin PCle power connectors.

Modular, semi-modular or non-modular

There are 2 different types of power supply: modular and non-modular. Semi-modular is a variant of the modular kind.

Modular: modular power supplies have a detachable cable so that you can add or remove power cables based on what you need in your computer. Semi-modular has one fixed power cable for the motherboard, whilst all other cables are detachable, so that again, you can add or remove them based on your requirements.

Non-modular: all the power supply cables are fixed, so you cannot change the amount. If you go for this option, you need to make sure there are enough cables for your requirements.

Energy efficiency

It is simple, a higher efficiency power supply unit consumes less power. In turn, this means that there is less heat generation and lower electricity bills for you. Win win! The power supply unit will be given a certification rating to show the level of efficiency. If the supply has a higher 80 Plus Certification rating, it will have a higher efficiency.


It is important to consider your budget when choosing a power supply unit. If you have a low budget, you may be tempted to go for a cheaper option, which is possibly unbranded. This is not advisable, as non-branded units could do more harm than good to the system. It is advised that you try and get a decent brand of power supply, to keep the components within the PC safe and working.



Although it might sound like there’s a lot to consider when choosing a PSU, it is important that you take the time to really find out what you need. It could be the difference between your PC working and not. If you are struggling and could so with some expert help, give servers and spares a call. We have a team of people who are experts in the industry and will be able to help  you find out what you need, and will be able to source the right product for you.