Is your computer shut down without any reason while you are enjoying the latest high end computer games? Added a new peripheral device that possibly hungry for power and make your computer system unstable or unbootable? Hard disk become undetectable while transferring files to it and it always crash on your computer? High chance that for all these minor examples mentioned are possibly caused by your inadequate power supply.
Taken from Wikipedia:
A power supply unit (PSU) is the component that supplies power to the other components in a computer. More specifically, a power supply unit is typically designed to convert general-purpose alternating current (AC) electric power from the mains (100-127V in North America, parts of South America, Japan, and Taiwan; 220-240V in most of the rest of the world) to usable low-voltage DC power for the internal components of the computer. Some power supplies have a switch to change between 230 V and 115 V. Other models have automatic sensors that switch input voltage automatically, or are able to accept any voltage between those limits.
The most common computer power supplies are built to conform with the ATX form factor. This enables different power supplies to be interchangeable with different components inside the computer. ATX power supplies also are designed to turn on and off using a signal from the motherboard, and provide support for modern functions such as the standby mode available in many computers. The most recent specification of the ATX standard PSU as of mid-2008 is version 2.31.
So, usually a normal home user will not need a giant power supply for the computer since their computer will not use much of the power supplied. However, if you were an experience user that had your computer plugged 6 hard disks, a few PCI peripheral device (sound card, USB extension card, TV tuner etc.), a latest and high end graphic card, but all powered up by a OEM/cheap power supply, then you have to think again. Since the cheap power supply (mostly power supply come with casing) is not designed to supply the peak power for long term, there is a high chance that your power supply will be failed even though it seems to be worked fine for you at the moment. Doesn’t believe? Head to eXtreme Power Supply Calculator Lite v2.5 and calculate by yourself for free. Although it will not accurately tells you what power supply you should get, but it give your a rough idea that how much your computer is demanding from your power supply unit. If your result in far less than your power supply rating, then there is no worry, although it is recommended to change the low range PSU once every two years or so. If your result is almost close or higher than what your power supply can offer, beware, change your power supply immediately before you made something you will regret for. Although most of the time during the insufficient power condition, the computer will turn off itself, but there are risks to burn/spoil your device too.
How to use the calculator site that I mentioned? Rather simple. The website had already has all possible combination of devices in your computer, so just select which matches yours. You might need a little bit knowledge on your CPU, RAM, Graphic Card as all these will obviously, affect your computer power usage. Below screen shot shown the part of the interface of the website:
After you had already selected all your computers’ devices, click on calculate and it will give you a recommended PSU wattage result. You can also print the result for your own reference or for the computer technician in the computer shop to have a look on your rig’s spec before recommending you any power supply.
I find this site is really useful sometimes when you want to replace a computer part and worry about the power usage. Of course to be safe, always purchase a branded power supply/true output power supply for your computer as they used higher quality material and has lesser failure rate, but they are not cheap either. So go on ahead, calculate, and have some idea on your computer power.