A power supply unit (more commonly referred to as a PSU) is an internal hardware component located in a computer that supplies the machine with power. A PSU converts a 110 – 115 or 220 – 230 volt alternating current (AC) into a steady low voltage direct current (DC) that the computer can safely use. A PSU is rated by the number of watts of energy it creates. A standard power supply unit can deliver about 350 watts of power. The more components you have on your computers, the more power it is going to need from the power supply. For example, if your computer contains CD and DVD drives, tape drives and ventilation fans, you are going to need a more powerful power supply unit. By utilizing a PSU that delivers more power than is necessary, you won’t be running at full capacity, which means that you lengthen the life of your unit by reducing the heat damage to the PSUs internal components during longer periods of use.

But, which type of power supply unit should you get? To help making the process of purchasing the best one for your needs, we assembled this handy buyer’s guide, which is full of valuable information pertaining to the purchase of a PSU.

Types of Power Supply Units

There are five different types of PSU units, including:

The Basic PSU

The basic PSU comes bundled with a computer case. It has several power cables, which come out and terminate different asymmetrical connectors, which ensure that they are properly orientated when they are inserted into the device. These cables have specific terminators that plug into the motherboard, disk drives and video cars. There are also ATX and BTX varieties; BTX PSUs are installed in the bottom of a BTX case, which ATX PSUs are installed at the top of a case.

Modular PSUs

Modular PSUs are outfitted with detachable cables, which allows you to remove any cables that you don’t need, which is very convenient, especially if you don’t want to leave those extra cables hanging out and risk being put into a dangerous situation.

Sleeved Cable PSUs

Some PSUs come with sleeved cables, or a flexible netting, which consolidates the cables. Sleeved cable PSU is a good compromise when you aren’t using a modular PSU. The netting also helps to conceal the cables, making them less noticeable and less of an eyesore.

High Performance PSU

For those who use their computer a lot, a high performance PSU is a great option. These PSUs are made in a different shape than other PSUs, which helps to maintain the temperature of the device. Because electrical flow is decreased when temperature increases, the unique shape also helps to increase the efficiency of the power that the PSU provides. The internal fan has more room, which gives the device better air flow, which is good for power management and for high performance; however, this also means that this type of PSU may not fit into smaller computer cases.

Laptop PSUs

Laptops, as well as netbooks, use an external PSU, which does not feature a fan. This type of PSU is a large block, which is encased in thick plastic or rubber. They tend to be cheaper than internal PSUs, and they supply less wattage, which is fine, because laptops and netbooks don’t need as power power as a desktop PC.

Factors to Consider When Purchasing a Power Supply Unit

There are a few important factors that you should take into consideration when buying a power supply unit. These factors will not only ensure that your device gets the proper amount of power that it needs to run, but it will also ensure safety. The PSU is the heart of your PC or laptop because it provides the energy to every component, which means that you definitely don’t want to ignore these considerations. If you do, you could end up dealing with expensive, annoying and even dangerous consequences.

The Wattage

The first factor that you should consider when choosing a PSU is the total wattage you will need. You can find plenty of power supply calculators online, which you can use to easily find how much wattage you need for your device. Once you determine the total wattage you need, you should take into account the total power, as well as a 20% buffer for safety purposes and any future proofing that you may need to do. Adding that extra 20% buffer will allow you to avoid having to buy a new PSU in the future if you decide to install upgrades later on.

The Efficiency

Power supply units can use a lot of energy, which can push up the cost of your energy bill significantly. If you want to make sure that your power supply unit won’t be a drag on your energy, then make sure you shop for one that has received a high efficiency rating.

Active Power Factor Corrector

The goal of an active power factor corrector is to ensure that the apparent power is equal to the true power. Also known as an APFC, this device corrects reactive loading from the wall outlet to the PSU, which helps to prevent energy from being wasted from the power supplier to the consumer, providing the device with greater efficiency. It also helps to provide the PSU with better voltage regulation while running at a slightly cooler temperature, allowing the PC to perform at a level that is as stable as possible.


You also want to make sure that you find out what type of modularity you need before you start shopping for a power supply unit. There are three modularity options:

The Price

You also want to make sure that you consider the amount that you want to spend on your PSU. These components can vary significantly in price and you don’t want to end up purchasing something that will overextend your budget.

Features of Power Supply Units

Power supply units can also offer different features. These features are intended to improve the ease of use, making them a better fit for your computer and your needs. However, do note that some features will drive up the price of the power supply unit, so if you don’t need them, you should probably shy away from PSUs that offer certain features, as you don’t want to end up spending more money than you actually want or need to.

Flat Cables

Some PSUs feature flat cables. When the cables are flat, it makes routing the cables underneath the motherboard, behind the motherboard tray and behind the drive bays much easier. Flat cables also allow for a more organized build and better airflow.

Industrial Grade Components

If you are going to be using your PC a lot, it’s going to generate a high temperature. A PSU that features industrial grade components will improve the safety of the unit when it operates at high temperatures. These components also help to prevent complications with performance and durability.

Fanless Modes

Some PSUs feature fanless modes. Their internal fans won’t run until they reach a certain internal temperature. This feature allows the PSU to operate at a much quieter level.

Thermal Control

This feature alters the fan speed based on the load on, as well as the internal temperature of, the power supply. The power supply is almost silent when it operates at low speeds, and during heavier loads, the fan speed slowly increases, helping to keep the power supply and temperature of the system low.

Best Power Supply Unit Brands

There are a lot of companies that manufacture PSUs, which can make finding the best one for your specific needs a challenge. We researched the various manufacturers and tested their PSUs, and we have determined that the following PSU brands are the best of the best.

Seasonic Prime

Seasonic is a known producer of components for computers. Their offer a wide range of PSUs, which are designed with the most cutting edge technologies and are based on the latest research findings. We liked how easy their PSUs were to set up, and how much power they delivered.


Corsair is another well known name in the computer component industry. Their PSUs are high quality and are made with exceptional craftsmanship. We also found that this manufacturer offers a wide range of PSUs to meet the needs of any user.


The PSUs designed by EVGA are known for offer high tolerance to extreme conditions. They are also known for being highly efficient and completely modular. We enjoyed how easy EVGA PSUs were to set up and use, which is why we think that they are the best of the best. We also liked that this company manufactures a wide range of PSUs to meet the needs of any user.