Guide: Power Supply Features

Power supplies are simple to understand but play the primary role in determine what parts and features you can use, as well as effecting general reliability. There are only a few things that you need to look at when choosing your power supply, but it is important to check them to ensure that the power supply will meet your needs.

Wattage: Ensure that the power supply's rated wattage meets the power needs of your computer. It's okay to purchase a power supply rated higher than what you need as well. This would give you more upgrade options in the future.

12v Amperage (And other amperages): The rail amperages are the maximum amperages any given rail can deliver. In some cases the amperage may be split between multiple rails for a single voltage. This shouldn't be an issue so long as you choose a reputable brand. Because the main power hungry components of a PC are 12v dependent, it is important to ensure that the power supply is capable of delivering most of it's wattage as 12v.

For example a Corsair CX 430 is rated for 32A on it's 12v line. This works out to 384w and is a fairly good ratio (about 90%).

On the other hand a Logisys PS550 is only rated for 25A on it's 12v line. This is only 300w (ratio is about 55%), which is less than the CX430.

Because the PS550 delivers less 12v wattage it is functionally worse than the CX430 despite being rated at 550w

Efficiency: Some power supplies are more efficient at converting AC power to the DC power your computer uses. more efficient power supplies generally are marked with the "80 plus" certification. This does two things for your computer. First and the most obvious is that it reduces your power bill. The second is that it reduces waste heat. In general "80 plus" and "80 plus bronze" are adequate for most builds, with the savings from a "80 plus gold" PSU often never being able to pay off their much higher price point.

Brand quality: This generally ties in with 12v amperage ratio and efficiency, but also effects reliablity and build quality as well. If you choose a reputable brand and product line, you generally don't even need to look at the amperage because you can  reply on them to be sufficient. Reputable brands include Corsair, NZXT, OCZ, Seasonic, and Antec. Brands that have some less than stellar product lines mixed in with good product lines include Cooler Master, Rosewill, and others. Pay attention to reviews to get an idea how reputable a brand or product line is.