Tips for Buying a New Computer Power Supply

The old saying that you get what you pay for definitely applies to computer power supplies. If you try to find a steal of a deal on a new ATX power supply there is a good chance you will regret it.

That said there is still more to buying a computer power supply than just looking at the price tag.

The most obvious thing to check for when buying a new ATX power supply is the power output. But the overall wattage on the front of the box is not as important as you might think. By far the most important power output number to check for is the +12 volt amperage. Whether the power supply is rated at 350 watts or 750 watts it won't make any difference if you don't have enough +12V.

On the side of the power supply there will be a chart with a whole bunch of numbers. Check for the +12V number. The power supplies +12V number must be larger than the power required to run your graphics card. If it isn't you are looking for trouble.

Everyday there are people who go out and buy the latest and most powerful graphics card only to find out their power supply can't handle it. It is not unusual for a high end graphics card to require 30 amps or more of +12V but there are lots of power supplies that only provide 25 amps or less of +12V.

Some power supplies have several columns of +12V numbers listed in their specs. These are called multi-rail power supplies. Explaining what that entails goes beyond the scope of this short guide. But usually you can add up the +12V numbers and go with the total. When you plug everything in you may have to balance the power draw on the different rails. Personally, I prefer going with power supplies that have one big fat +12V rail. 40 amps of single rail +12V is usually enough for most single graphics card computers. Your computer's processor, fans and drives also run on +12V so make sure you have plenty to spare.

The other big problem with power supply specifications is the reliability of the numbers. The specs on the power supply are the manufacturers claims. Very often the claims are exaggerated or outright false. Electricians who test power supplies frequently find cheap power supplies fall well short of manufacturers claims, whereas more expensive ones meet and usually exceed specs. Here again, you get what you pay for.

The other big thing to look for when buying a new ATX power supply is the number and type of connectors. Especially the graphics card power connectors.

The biggest power hog in your computer is probably your graphics card. The newer graphics cards are more power efficient but their overall power requirements seem to keep going up and up. Because of this the number and type of graphics card power connectors coming out of your power supply have had to change as well.

Some graphics cards require 6 pin power connections. Other newer ones require 8 pin connectors. Some need only one connector while others need 2. So study the details of your power supply and graphics card and make sure you have all the connectors covered.

Some power supplies are modular. What this means is you can remove the extra connectors you don't need. The cables plug into the side of the power supply. You simply unplug and set aside the ones you don't need. This makes it much easier to arrange the cables inside your case and maintain good cooling fan airflow.

Modular power supplies, however, are not functionally superior because of this feature. If you are on a tight budget, get a better non-modular power supply and spend a little extra time tidying up the cables in your case.

Getting a good deal and saving some money on a graphics card, cpu or motherboard makes sense. But make sure you spend those saved pennies on your new power supply. You will be glad you did.