DO NOT Cheap Out On Power Supply Unit


Several years ago I used to frequent a lot of computer hardware forums. In these forums people discussed everything related to computers. But the highest number of threads, especially from new members, used to be about malfunctioning computers. The complaints ranged from frequent blue screen of death (BSOD) to random shutdowns.

Strangely, these are the type of complains that I also hear from people who want to buy “only branded computers because assembled ones have issues”.

Yes, these problems are real. In majority of cases they affect assembled computers.

But it has nothing to do with the fact that a machine has been assembled. Instead, in most cases, these problems can be attributed to poor quality of power supply unit (PSU) aka SMPS in a computer. This is one part with which 90% buyers go wrong and computer sellers happily oblige because they have fat margins on poor quality PSUs.

A PSU is one of the least understood computer part. It is not as sexy as a CPU or graphics card. So, most users don’t pay any heed to it. Even geeks, who know a thing or two about computer parts, don’t bother with it. Result: An extremely unstable machine and a huge risk to the whole computer.

At the same time, there is also other side to the story. This is about people who know somewhat about PSU and understand that it is important. Many computer hardware enthusiasts are part of this tribe. The people select a super powerful PSU that can deliver a truckload of current. This, though better than picking a cheap PSU, is a waste of money.

Before I talk which PSU I selected for my new computer, here are some basics on PSUs.

-- A PSU is one of the most important components in a computer. It powers every other component and a faulty PSU is a risk to the whole computer.

-- PSU is one component where the more you spend, the better quality you will get. Up to a reasonable extent.

-- You should not power your computer, however basic, with the no-name PSU that comes bundled with a chassis. Just stay away if these chassis happen to be from VIP, Mercury, Zebronics and Intex etc.

-- It may sound strange but weighing a PSU can tell you how good it is. Heavier = Better. In most cases.

-- Cooler Master, Corsair, Seasonic, Antec are four brands I suggest as far as India is concerned. Abroad, you also have access to excellent BeQuiet, Enermax and PC Power and Cooling. However, stay away from XtremePower series of Cooler Master.

Now let me move to a little technical stuff. It’s very important.

-- Wattage doesn’t mean a zilch. Let me repeat, buying a PSU on the basis of its wattage is the most foolish thing you can do.

-- If wattage is not important, than how do you judge a PSU? In a PSU, the most important factor is quality of its component. The ideal way to see that is to open the PSU and look at what has been used and how it has been assembled. But that is not an option. So, apart from reading a review or two, you can take a look at the effective wattage and efficiency.

-- Effective wattage is determined by temperature. Did I tell you that you should stay away from no-name PSUs? The reason: Their wattage is often the one that they can deliver at a temperature of 25 degrees Celsius, which is never going to be the temperature inside a computer. Ideally a PSU should be able to deliver the rated wattage at 40 degree Celsius or more.

-- Never buy any PSU that is not rated to provide stated power at at least 40 degree Celsius. Check manufacturer’s website for this info. If it is not available, don’t buy the PSU. If you are building a high performance computer, select a PSU that can deliver rated power at 50 degree Celsius. 

-- Nowadays it is stupid to buy a PSU that cannot provide at least 80% efficiency at any level of load. Bonus: Let me explain efficiency to you. It is the power a PSU can convert from given amount of AC to DC. Computer parts cannot run on AC. They require DC. That’s why laptops come with power bricks. So, if a PSU has 80% efficiency rating, it will require 100W AC power (from the plug) to supply 80W to the computer. Better efficiency means lower power bill. Many no-name PSUs don’t even have 50% efficiency.

-- Forget the total wattage. But understand how much current is available on +12V rail(s), which serves CPU and graphics cards, the most power hungry components in a computer. A reasonable decent manufacturer provides this information about a PSU. But even if only the amount of power amps is available, you can calculate it. For example, if a PSU can supply 30A on 12V rails, it means the total wattage available to a computer on this rail is going to be 30 x 12 = 360W under ideal conditions.

-- In a PSU, look for overvoltage protection and short circuit protection etc. In future, this can save your computer.

-- Let me repeat again. Wattage is not important. But it is crucial that computer parts get clean power. This means the power should not have ripples or noise. The quality of power depends on quality of components in a PSU.

-- Optional: Get a PSU with modular cables, if you want to minimize cable mess in your computer. But it is a purely aesthetic feature. Modular cables have no affect to power supply. 

Calculating how much power your computer needs

While wattage don’t really matter, you should still make sure that you have a power supply that can feed your computer. You remember I talked about the instable systems in the beginning of this piece. Most of the problems occur because PSU can’t keep up with the power requirement. Dirty power kills systems over a period of time but lack of power leads to immediate crash or shutdown.

There are several ways to calculate how much power your computer needs, but I am going with the easiest route. A graphics card is the most power hungry component in a PC. I am assuming that a high-end card will be paired with high-end components and low-end with mainstream parts. We can use this to roughly determine how much power your computer is going to require. 

-- Computer with no Graphics card: At full load this computer will require around 120W power. For this computer you are fine with a good PSU of around 300W.

-- Computer with a low-end graphics card: I am terming all the graphics cards that don’t require separate power low end. This computer will use a maximum of around 160W. A good PSU of 350W will handle it fine.

-- Computer with mid-range graphics card: These are the cards that require one six-pin connector for extra power. This computer will use a maximum of around 230W. A good 400W PSU is enough.

-- Computer with a high-end graphics card: The card here requires two six-pin connector or 8-pin connectors. This computer will use a maximum of around 350W. A good 550W PSU is enough.

-- Computer with multi-graphics card: Well, this depends on the type of cards. But assuming they are the top of the line, high-end graphics cards, the computer will require around 600W at its full load. A good 750W PSU is enough to deal with it. 

The PSU I bought: Seasonic X-560W

For PSUs, I value quality over quantity. Especially because when push comes to shove — feeding the system when I am gaming for hours at end — quality matters. Reviews of Seasonic X-560W tell that it is rock solid in terms of ripple and noise. It delivers clean power, has a hybrid mode where its fan starts spinning only if the load is above 20%, has superb efficiency of over 85% and comes with all the features like overvoltage protection, surge protection, short-circuit protection etc. It also has a fully modular cable system and five years warranty.

Given that I am using just one graphics card, 560W is enough for me. In fact, such is the quality of this PSU that if required, it delivered up to 730W despite a rating of 560W! The only problem with this PSU: It costs a hell lot of money. For example, a 600W Cooler Master PSU (low end series) is available for around Rs 4,000. This Seasonic costs around Rs 7,000. But of all components, this was the one on which I did not want to make any compromise.

Some links:

System Wattage Calculator: It errs on the side of caution and give you around 50W more than you require but is decent tool to use before you buy a new PSU 


Review of no-name PSU: Read it to know what can happen if you run your computer with no-name PSUs. Skip to conclusion if you want to avoid the technical details. 


Review of Seasonic X-560W: If you are interested


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3 Responses to DO NOT Cheap Out On Power Supply Unit

  1. Nice information thanks for sharing it..!it will be helpful for people searching this kind of information..


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