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Power Supply Unit (PSU) buyers Guide


     When buying any computer component it is important to make sure you are getting exactly what you want. This is even more important when dealing with a Power Supply Unit. The Power Supply Unit or PSU is most likely one of the least thought about computer part when making a purchase but buying the wrong PSU can be disastrous not to mention expensive in the long run. It is hard to know exactly what you need without over spending so here are a few tips to make that purchase a little easier.


     The first thing you need to find out when buying a PSU is what are you requirements. TO find this out make a list of the components you are planning on putting in the PC including extra fans and extra peripherals like hard drives CD-ROMs USB devices anything that has a power plug or draws power. After you make your list find out if the perspective PSU has the number of physical plugs and type of plugs you will need. Example: 4-pin Molex 12v, SATA 12v 3-pin 3.3v, 4pin 5v and so on.


Standard 4-Pin 12v / Floppy / Serial ATA / Aux Power / Molex Connection

     Next is the power requirements take the minimum specs on the motherboard for example is it a 20 or 24 pin is there an extra 4 pin 12v connector for the Southbridge and so on. When you r list is complete then you need to decide what Wattage would work best for you. Take the minimum needed for the board and CPU generally stay around 250 to 300 Watts with 939 socket or older. Then take all the extras and add them together so for example I am using 4 SATA hard drives using 12v power Two DVD ROMs using 4 pin 12v power three extra 3.3v case fans and USB extras like a Printer and Digital camera. My rule of thumb when adding these devices together is for every 12v device or 2 3.3v / 5v device that draws .5 to 1 amp you add 20 Watts from your base now the Base is generally the Motherboard One IDE or SATA Hard drive and one IDE or SATA CD plus video and One Case Fan so in my situation above there are 3 extra hard drives one extra DVD and add 2 case fans so that is 4 devices extra or 80Watts over the base of 250 to 300 Watts making a minimum of 330 to 380Watts add in a few for USB devices and it is easily 400Watts. Now this is how I try and even things out I am sure there is an equation that an electrician can explain but these rules of thumb have always kept my systems running with ample power.

 More information on wiring and hook PSU hook up.

     The next step once you have the connection type and Wattage taken care of is the take into consideration future compatibility or do you plan on expanding at all. It is generally a good Idea to just add 10 to 20 percent onto what ever you end up figuring your requirements are in my situation 400 Watts is a good starting point for the hardware being installed and 10 % or 400 is 40 so to be on the safe side lets use 20 % or 80 Watts so I am at 480 Watts.



     Now that you know the range (Wattage) and you have an idea of physical connection next is deciding what one to buy. Your choices consist of Silent Radiant (fan less), Adjustable fan speeds models, removable power connections and so on. Oh at this point Price comes into play. Make sure you shop around. Here are a couple considerations for the final decisions on what PSU to buy.


     For a fan run Power supply make sure the fans are reliable see if the manufacturer gives information as to the life expectance. This is extremely important when buying a basic CompUSA special or Generic PSU. The reason is simple the number one failure in a PSU is heat. Heat can cause not only the PSU but the components inside the PC to fail as well. So a good fan can be the difference between a 1year unit and a 5year unit and in some situations a hole new PC. Second thing to consider with a Fan PSU is location are you going to be cleaning this unit routinely or is it going to be in a corner with poor airflow this can cause a fan to die prematurely so location or proper maintenance could be a factor.


     As for the Radiant units or the fan less power supplies obviously you are going to pay more and in general they run a little hotter but have a better life expectancy due to the durability. Also make sure it is an aluminum case unit they cost more but if going the fan less rout price should not be a consideration.


      The Adjustable fan speed models have a wide range what sets these apart from your stock 80mm models are two factors one generally there is a second fan ranging from 80mm to 120mm and in most situation there is an adjustable speed to allow the consumer to control the noise and cooling power. These PSU’s generally cost a bit more and have a higher maximum Wattage. This is based on the fact that less heat allows for more power. Again like in the stock PSU make sure the fans have high life expectancy and it is even more important to keep these units clean. The more air you move the more dust you collect.


     There are also for the serious power users dual stage and redundant power supply units but this article is really not intended for that type of users these units are generally very high priced and used on servers. For more information on server PSU’s just Google dual stage or redundant power supplies.


So to recap the major factors when purchasing a Power Supply unit are.

  • Price

  • Number and types of connectors needed

  • Wattage requirements for the hardware

  • Type of unit (Fan less, Stock / Generic, Adjustable with extra fan)

  • Last what extras are needed (Lights, Removable Cable, Fancy Colors, and so on)

Here is a listing of Power Supply Reviews we have done in the past that might help.

08-26-05 OCZ 420watt ModStream ATX PSU Review

02-16-05 XG Vortecr 500watt PSU Review

01-29-05 COOLMAX Fan-Less 350watt PSU Review

12-30-04 Xtreme Gamer Vigor 450watt PSU Review

09-17-04 FrozenCPU UV Reactive PSU Covers


I hope you find this article useful if you have any questions feel free to contact our staff and thanks for reading.


Marns CDA





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