I get really annoyed at your basic ‘whitebox pc system’ pushed onto consumers. Why do the shops insist on putting crap power supplies into their systems. Ok, I know why. They’re cheap or have a good store profit margin. Sadly in reality many of these generic power supplies are just pieces of crap.
When choosing your system you need to remember that the power supply provides the ‘life blood’ that your system runs on. An old adage is ‘Garbage In, Garbage Out’, with the Garbage Out in this case being represented by shortened component life times or spurious failures. If you consider this then the power supply is arguably one of the most important components in your system.
Sadly, along with other computer components there is a bewildering array of choices. This makes the task of selecting a power supply a difficult decision. In order to assist, i’ve put down some thoughts on areas where you can focus your research and streamline the process a little for you. Please note that if you follow this advice, do all the research and the system still eats your children then it’s not my fault 
- Attempt to estimate the likely power consumption of your system. There are a number of web based forms where you type in your system components, click a button or two and some magic occurs leaving you with an estimate of your systems power consumption. These tools are a good first step. They don’t provide a complete picture, but they do provide valuable insights which in turn will lead you to asking more questions – trust me, this is a good thing! An example site is the Extreme Power Supply calculator over at the Antec website. More detailed analysis is definitely required as the total system power is consumed via a number of supply rails (3.3V, 5V, 12V etc) and it is extremely important to ensure there is sufficient capacity on each of the rails for your system. For example, if after analysis you find that your system requires 14A on the 12V rail then there is no point using a power supply that can only deliver 10A – even if that power supply is advertised at delivering the total wattage for your system.
- Look for the power supply that is likely to be the most efficient for the typical operation of your system. Current power supplies typically have their highest efficiencies around 50-70% of their peak loads so you should consider a power supply where your nominal system load operates in the power supplies most efficient region thereby reducing your operational power costs. But please, still take into account your systems peak needs as there is no point having a system that runs efficiently most of the time but can’t deal with all the power demands you may impose from time to time.
- Make sure your power supply is at least 80% efficient in your operating range. The difference in price between a piece of crap supply running at 70% and a slightly more expensive 80% efficient unit will most likely be recovered in <3 yrs through reduced power costs. For more information on energy efficient supplies check out the 80 Plus website.
- Don’t simply trust manufacturers claims, in fact don’t trust mine – you’re clever enough to figure this out for yourself If a manufacturer says this power supply is rated at 550W then you should consider that to be exaggerated in potentially several ways. For example, it may be referring to an operating temperature which is completely unachievable in normal pc’s
- Check you have enough connectors to power all your devices. Sounds obvious, but trust me (or not ) some power supplies only come with limited connectors. Do your best to avoid so called modular plugs or adapters as these simply increase electrical resistance wasting power better used by your devices.
- Make sure the power supply fits your case – should be obvious, but shit happens and sometimes you forget simple things.
If all this is proving difficult for you to figure out then see if you can get your supplier to do the analysis for you. If they don’t know how, then you really should be asking them – How do you know that supply is ok for the system you’re trying to flog me?
Good Luck and if you don’t take anything else away from this blog entry try to remember that you’re in charge – make an informed decision.
