Computer Power Supply Guide

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Computer Power Supply Guide

A proper power supply is an essential part of anyone's computer. With a failing power supply, the computer may end up crashing, causing you to lose valuable work and time. With this in mind, it's important to replace your computer power supply for your own peace of mind.


Form Factor

Finding a power unit for your computer in online stores is easy if you know your computer's form factor. Form factor will help you determine the type of power unit that should be purchased for your computer. The term refers to the specifications of the motherboard, including dimensions, power supply type, number of ports on the back panel, and the location of mounting holes.

It may be possible to find your computer's form factor on the manufacturer's website; if not, it can be determined by contacting the manufacturer directly. Today there are two main types of form factors: the ATX form factor and the BTX form factor.

ATX Form Factor

ATX is the most common form factor found in power supply units. Typically, an ATX model runs about 14 centimeters deep, depending on the wattage that it offers. ATX offers backwards compatibility and increased drive locations.

BTX Form Factor

The BTX form factor is less common than the ATX form factor, but it's often found in Dell computers. The BTX form factor is known for its superior cooling capabilities. The BTX is essentially the ATX flipped upside down, which directs the coolest air straight into the processor.


Factors to Consider When Replacing A Power Supply

While looking for a computer power supply, three valuable features to keep in mind are its power output, rails, and efficiency.


Desktop power supplies typically have an output rating that spans from 300 watts to 800 watts, depending on the specific model. In an ideal situation, the power supply will deliver the desired amount of power to the computer's programs and have extra left over in the case that further components need to be added on. When you select your power supply, you'll want to assess how many components and programs you typically use while on your computer. Keep in mind that power supplies usually reach their peak efficiency levels when they are being used at 40 to 70 percent of capacity.

It's also important to remember that power supplies with higher wattage do not consume more power than ones with lower wattage. A system's components are what dictate its power consumption. If there are 600 watts worth of components in the system, it will consume 600 watts whether the system has a 600 watt supply or a 100 watt supply.


A power supply's efficiency rating refers to the percentage of wattage that powers your system and is not lost as heat. The ideal efficiency rating is at least 80 percent, meaning that 80 percent of the wattage is used to power the system while just 20 percent is lost as heat.


Power supplies are either single rail or multi rail. As the name implies, a single rail power supply has one rail to bring power to your computer's system components. A muti rail power supply divides the output between more than one rail.

Both models have advantages and disadvantages. With single rail designs, all the power is available for any component connected to the computer, no matter which cable is used. Should the power fail, however, a single rail power unit can potentially overshoot power into your components and cause problems. Multi rail units cannot share power between their different rails, which can sometimes be an inconvenience.

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