This article I wrote was inspired from my CPU Wattage article and "You Got The Power" article from PC Power & Cooling, Inc. And it also based on my real experience on May 2002. If CPU Wattage article discusses the power consumed by processor, this article discusses the power consumed by other peripherals such as motherboard, RAM, graphic card, I/O storage, etc.

It's very irony if you decided to buy a killer PC which assembled from newest peripherals such as P4 3.06GHz processor, GeForceFX graphic card chipset, RDRambus Memory system but you buy lack, cheapest power supply because of budget reason.

If you think that power supply is additional peripheral, well, you will get serious problems toward. Power supply is the vital peripheral like motherboard and processor. So the question is "Why does it so vital? What will be happen if we use lack power supply?"

Motherboard, processor and other peripherals need enough electrical power to operate (commonly specified in watt unit), if the power supplied is not enough, they can not operate well, and it affects system performance and stability. Your system is often restart, suddenly, and it is possible that your pc will not be powered up.

In fact, some blue screens, unstable drivers, or Operating Systems itself can actually be power supply related. Witness the problems that Athlon-based systems have with power supplies that lack ample wattage. So you need power supply which can provide enough power for your peripherals. If you run Pentium4 or Athlon based system, make sure you use at least 300W power supply.

But if you affraid that running "high wattage power supply", 425W for example, will increase your electricity bills, fear not. A "switching" power supply technology only pulls out what's needed. If your PC needs 200W total, but you have a 400W supply, the system will only consume 200W. The power usage is based on peripherals demand, it only used when the peripheral is operated, and every peripheral has specific power needs. Running system on standby mode will consume less power and running benchmark test will consume more power. In fact, some power supply vendors say the extra breathing room can actually save you money because the more powerful unit will run cooler and more efficiently than the cheap power supply.

So, how much power do you need? If you're running a micro-ATX motherboard with embedded graphics and audio, and a single 5400rpm IDE drive, that 150W power supply may be sufficient. But if you installs half a gig of RAM, dual processors, Ultra2 SCSI RAID, and a GeForce4 graphic card, even a 300W power supply may hang your system.

Here the compiled list of peripherals power demand. By now you should know not to judge your power supply by overall wattage alone, so look at the demands on each separate line. Nonetheless, when looking at overall wattage, add the requirements of every device in your rig, then multiply that number by 1.5 (because you should be taxing from 30 precent to 70 percent of your power supply's capacity). Some of your individual components may actually list their specific power requirements, so use these numbers specified for more accurate calculations. And remember, if you need to figure out wattage, multiply the voltage by the amps.

More about processor power consumed, you can read my CPU Wattage article. If you want to know about processor details, go to x86 Processor section. You can also read related article about notebook power consumption.