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Written on July 31, 2006 by Richard Millard
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The power supply fills a very specific and important role. The power supply is designed to convert 120 V or 240 V AC power (which is what comes from your electric company) to usable power for the internal components of the computer.
I really consider this to be the most important and most underrated section of the entire computer. If you're skimming the article, I'll throw this part in bold so that it stands out: The Power Supply is not the place to cut corners!
Like cases, there's a huge array of Power Supply Units (PSU's) out there. Looking around, I can find $20-case-and-psu packages for sale. A good quality power supply from a reputable dealer starts at about $80, and can scale all the way up to several hundred dollars for extremely high-end models.
Many system builders try and cut corners here by using poor quality, cheap power supplies. I can't stress enough what a gamble this can be. The power supply is the electrical source of your entire system, and you can imagine the havoc it can cause if there is inconsistent power being supplied to your hardware. A standard electrical signal has frequent and periodic "spikes" and "surges", both of which can be incredibly damaging to your hardware if your PSU doesn't properly filter them out.
Every power supply has three factors that are important to consider.
The first is the Wattage. All that is important here is making sure that your PSU has enough power to supply your hardware, plus any upgrades you might be considering.Figuring out the wattage you need can be tricky, so don't hesitate to ask a salesperson what sort of wattage your system will need. There are tools available to help you with this, but they can get pretty complicated. If you're really interested, you can check out one here.
The second important factor: efficiency. Some power supplies are highly inefficient, which means they're sucking up more juice and outputting heat! Personally I'm not a big fan of paying my electrical company to heat my apartment via my power supply, so I aim for the most efficient power supply I can find.
The last key item to consider: MTBF - Mean Time Between Failures. This is simply the average lifespan of that particular power supply. Some companies might not be very forthcoming with this information, but it's a great number to ask about. A bigger number is better - you want the longest average time between failures that you can find.
First and foremost, you need a power supply with a reputable brand name. It should also come with a good manufacturer warranty.
Determining the size of the power supply that you need can get pretty complicated. You can use the power supply calculator listed above (but you might want to overshoot that number a bit, to leave some room for growth).
When choosing your power supply, keep in mind your upgrading needs. Perhaps your system only needs a 350w power supply currently, but in the future, are you going to add a second video card, two more hard drives and some more RAM? If so, leave yourself some room to grow. Upgrading a power supply can be frustrating because it requires rewiring the entire system.
Aim for a power supply with a bottom-facing 120mm fan, rather than a rear-80mm fan. You'll find it has terrific cooling, and is much quieter.
PSU's, being a self-contained unit, all appear the same on the outside. The only way you can really be sure you're getting a quality unit, is to shop for a reputable name brand. As far as name brand power supplies, here's some of the best:
PC Power & Cooling - Hands down the best power supplies on the market, but also extremely expensive and quite loud.
Seasonic - This is the power supply I recommend to anyone and everyone. Great bang for your buck, extremely high quality, and a phenomenally low failure rate. Out of thousands we've sold, we've seen less than 5 ever have a problem.
Antec - As with most of their product, they put out a high-quality line, and a very poor quality line. Their NeoPower, Phantom and NeoHE series is very popular, and does a bang-up job - But stay away from the SmartPower series.
Enermax - Same as Antec, they have some quality lines, and some value lines. With power supplies, I'd aim for the quality lines, like the "Liberty" line.