Size of Computer Power Supply

The proper computer power supply sizes is determined by the number of components your system has. For modern computers, you will need at least a 300 watt PSU (power supply unit). Note that this is the usual minimum. If you plan on upgrading, get a bigger PSU.

How to Determine the Right PSU

The easiest way to do this is to go online. There are several free PSU calculators you can use. The process involves specifying the hardware you have and then just click “calculate”. The results may differ per site, so check a few. Always go with the highest recommendation given.

Choosing the Right Power Supply

Aside from the wattage, other factors have to be taken into account. For example, you need to be certain the device can fit in your computer. The connectors must also be appropriate.

What the PSU Does

The PSU changes the AC (alternating current) at the plug outlet into direct current (DC). This is the element required by the computer parts to function. Whatever the computer power supply sizes are, it is also responsible for setting the voltage into the proper levels.

Majority of power supplies are equipped with fans. This is necessary to keep the device cool as it operates. There are also fanless systems available.


Power supplies are sold in different form factors (sizes and shapes). Be certain the PSU form factor is compatible with your casing. An over sized form factor will make it impossible to fit the device inside. The most widely used form factor is Advanced Technology Extended (ATX).


The PSU rating is based on watts. As stated earlier, the components inside the computer determines the amount of wattage power needed. Systems with multiple hard drives, high end video cards and powerful CPUs will need a lot of wattage power.

Manufacturers analyze the PSU under diverse conditions. Poorly made PSUs have imprecise ratings. A high rating is recommended as PSUs are most proficient at high loads.


Ensure the connectors are suited for your motherboard. Different motherboards may require unique connectors. Some are modular so many kinds of connectors may be utilized.

A PSU with 80 PLUS certification means it is energy efficient. If saving electricity is a concern, this is something you should take into serious consideration.

The importance of picking the right computer power supply size cannot be overestimated. Choosing the wrong one can damage the whole system.

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