Power Supply Units

PC Power Supply Units – a guide on selection

I’ve been building desktop computers since I was a kid. It’s fun to select components, do the research and the thrill of turning the computer on for the first time, installing Windows (or your favourite Linux distribution) and then setting about to customising it properly. While we all enjoy fiddling with the exciting components, a lot of people tend to forget or skimp on something really important: their power supply units.


But it’s important not to neglect the part of your computer that controls all of the electricity in your computer. You want to make sure that whatever you are putting in there is reliable and isn’t going to damage your precious, and most likely expensive components.


Know your component requirements

It’s really important from the start to know how much power your computer will consume at maximum operation. Thankfully, there are free online tools to help you out in this task. One of the better ones is the calculator provided by Cooler Master, though you’ll end up getting a recommendation for one of their power supply units as a result. Another tool, which is newer and also includes factors such as aging of components, is by OuterVision.



Both of these tools allow you to select the kind of components you plan on putting in your build. You can even include things like LED lights, case fans and liquid cooling systems. They will then give you a total wattage requirement for your system. The Outervision version also gives you a recommendation on a UPS should you plan on leaving the PC on the majority of the time.


Now that you know the maximum power of your computer system, it’s time to actually choose a power supply unit. This is where it gets tricky, because of all the brands, ratings and marketing. Here, I’ll hopefully be able to dispel some of the hype and myths.


Power supply units – Wattage

If you’ve gone in search of power supply units, you’ve probably seen the variety of brands, power wattages and other kinds of ratings. First thing is first. There are a myriad of reputable, high quality companies that make power supplies. Many of them also make other things for desktop PC enthusiasts, like cases, graphics cards and memory. These companies all trade on their reputations, and a purchase from them should be reasonably safe.



There are a few things to remember though. Just because your maximum power usage says 450W, doesn’t mean you should get 450W power supply units. While the unit in question will be able to provide your components with 450W of power, having something sensitive such as electronic equipment operating at the edge of its capability is risky.


Instead, always pick a power supply unit that has a maximum supply wattage above what you actually need. First, it eliminates the risk of you frying components. Second, you might want to add something later on, like hard drives or more memory. Headroom is really useful in these cases, for obvious reasons.


Power supply units – Ratings

The other thing you need to consider is the “rating” of the power supply. If you’ve been browsing the available products at online stores like Newegg or Amazon, you’ll notice many have an “80 Plus” rating. This relates to the efficiency of the power supply units in question. Now you may ask what I’m talking about. The short answer is that nothing is ever 100 percent efficient, and power supply units are no different.



When your computer is on, the power supply unit will pull power from the wall to satisfy the amount required at any moment in time. However, what your computer components receive is always less than what the power supply is drawing from the plug. That’s because the components and conversion between voltages and current are never perfect. Your power supply unit generates heat when doing its job.


The “80 Plus” rating is guaranteeing that your power supply unit converts at least 80 percent of the power it draws from the wall to power used by your computer at specific loads (20 percent, 50 percent and 100 percent). There are six levels of certification, and information can be found about them here.


In conclusion

I hope this gives you some idea about power supplies and how to choose one for your computer. I just want to point out that there’s no perfect power supply. As long as it meets your budget, power requirements and your efficiency requirements (if you care), then that’s more than fine.

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