PC Hardware

Power-Supply Wattage

Power supplies are rated according to the maximum sustained power (given in watts) that they can produce. A watt is a unit of electrical power equivalent to one volt-ampere. It is important to keep in mind that the power supply must produce at least enough energy to operate all the components of the system at one time.

Don't rely on the computer's operating consumption alone, which can be obtained by adding the requirements for the devices in the PC. Remember that a much larger drain occurs as the machine powers up, when hard drives and other heavy feeders simultaneously compete for the available startup power. Most general-use computers require 130 watts while running and about 200-205 watts when booting. Sound cards, modems, and (worst of all) monitors attached with an accessory plug in the case can push a weak power supply to its limit and beyond.

Servers and high-performance workstations often have an abundance of RAM, multiple drives, SCSI (Small Computer System Interface) cards, and power-hungry video adapters, along with one or more network cards. They often demand power supplies of 35-500 watts.

The label on a power supply that says "Don't Open" means just that! Opening a power supply is dangerous. It is better to completely remove and replace a defective power supply as needed.

Components power consumption

  • Motherboard: 50 to 150 watts

  • Processor: 80 to 140 watts

  • RAM: 15 watts per slot

  • Fan: 3 or 4 watts per fan

  • Hard Drive: 20 to 30 watts

  • SCSI: 20 watts minimum

  • CD/DVD ROM: 20 to 30 watts

  • PCI Card: 5 watts per slot

  • AGP: 30 watts minimum

  • PCI Express: 50 to 150 watts