The computer power supply unit (PSU) is a very important component in your computer. It gives your computer the juice it needs to run properly and efficiently, a bad power supply choice can break your computer beyond repair if you’re unlucky. The computer power supply takes the AC current from the wall socket and converts it to DC current so your computer can use it. Most computer power supplies are built to conform with the ATX form factor.

Computer Power supplies are rated by their maximum output power. The typical computer power supply wattage ranges from 300W-1000W. Those that have computers running several processors or graphics cards will be using more heavy duty power supplies so they need the 1000W.
Computer-Power-Supply
In order for computer power supplies to deliver the power to the computer they need to have a certain amount and kinds of connectors. They typically have the PC Main power connector, ATX12V 4-pin power connector, 4-Pin Peripheral power connector, 4-pin Floppy drive, Auxiliary power connectors, Serial ATA power connectors, and an additional 6-pin connector. The PC Main power connector connects to the motherboard and gives it power, it usually has 20 or 24 pins. A power supply connector with 24 pins can plug into a motherboard with 20 pins, and if the power supply has a 20-pin connector it usually has an extra 4 pin adapter just in case. ATX12V 4-pin power connector is a second connector that goes to the motherboard. 4-pin peripheral power connects (Molex power connectors) are smaller connectors that go to disk drives, fans, and other smaller devices inside the computer. The 4-pin floppy drive power connector (Mini-connector) supplies the floppy drive with power, and can also be used as an auxiliary connector for AGP video cards. There are several different kinds and types of auxiliary power connectors designed to provide additional power if needed. The SATA computer power supply connector is a 15-pin connector for SATA components. The 6-pin connector is generally used for PCI Express video cards, and there should be a new 8-pin connector showing up on the latest computer power supply models.

Computer power supplies give voltages of +5v, -5v, +12v, -12v, and +3.3v. This is important to know so you can test a computer power supply with a voltmeter if you think it is causing problems or not performing as well as it should be.

When buying a computer power supply what should I consider?

Computer Power supply labels are deceiving: There is no standard measure for testing power supply wattages, or no standard rating system for computer power supplies, so you need to be careful when buying computer power supplies, because companies are squeezing as much juice as they can possibly can out of them so they can rate them higher. If possible read magazine and internet reviews on the computer power supply so you can get a better feel of it’s real life performance rather than testing conditions from an objective source.
At least 500W for the average system, more if you’re a gamer: For an average system I recommend looking at getting a computer power supply that is rated for at least 500 watts, this is a good safe zone, it’ll prevent you from having to upgrade again in the near future, and should have enough power for any extra devices you want to add onto it like an extra DVD burner, hard drive. If you’re planning to game don’t go cheap and forget to invest in a quality computer power supply, at least rated at 600 watts, you’ll need a good computer power supply to handle your video card, and an even better power supply if you’ll be running two video cards.
Make sure it has all the connectors you’ll need: Take your time when buying a computer power supply and make sure it has all the connectors you’ll need, if you’re running a newer processor, or a PCI Express graphics card you’ll need the extra 6-pin connector that doesn’t come on every power supply, so be careful and always double check.

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