How to choose the right power supply for your PC


How to choose the right power supply for your PC

So, you need to know how to choose the right power supply for your PC?  Well, if you stick around ModCrash you’ll hear me say this a million times, the one item you should never go cheap with is your power supply.  I will probably repeat that a million more times, but let me break it down easy mode, then I will explain why.

  • Important Factors when learning how to choose the right power supply for your PC
  1. Wattage (i.e. 350w,500w,1000w)
  2. 80+ Rating Certified
  3. Known brand with proven track record
  4. Power inputs provided vs your requirements
  5. Thermal output

That is really the only important items when learning how to choose the right power supply for your PC.  If you take the time to read through this article, you will not only potentially save your computer from a blazing inferno, but you might also save some unnecessary power consumption, therefore saving you some cash.  By the time you finish this, you should feel comfortable knowing you know how to choose the right power supply for your PC.



The first step in learning how to choose the right power supply for your PC is to establish how many watts you will require for your complete build.  There is a few ways to go about this, but for the sake of argument  am going to stick with one method.  Research the components you plan to install in your computer and find out their maximum power consumption.  Add all that together and you have your maximum load.  From there you can get an idea of what size power supply you need.  Keep in mind you will probably want a little more than that, I will cover that in the next section.

  • Factors that can increase the amount of watts required
    • Overclocking – When you increase the voltages to any component within your computer, you’ll start consuming more wattage.  There are programs that can show your power consumption on some components, such as HWMonitor.
    • Plans on adding additional hardware – If you are actually listening then you are not planning on buying something cheap.  Since you are not buying something cheap, you should get something with a lot of extra headroom (wattage) for future builds on top of some other beneficial factors.  I recommend double what you expect to consume on an average day.

Power Loss and Thermal Properties


Now, there are a few things you will need to really think good and hard about before jumping the gun and buying a power supply.  There’s this little certification out there called “80 plus”.  80 Plus was launched in 2004 as a method of certifying the end user understands how much energy is wasted by their PSU.  The bottomline, do not buy anything that doesn’t hold an 80 plus certification.

Energy efficiency

How to choose the right power supply for your PC

Thermaltake’s Toughpower XT 80 Plus Platinum rated 1275W PSU


So what does 80 plus mean and why do you need it?  80 Plus means your power supply is 80% energy efficient.  Okay, that probably didn’t help.  Let me use an example.  Say you have a 100w power supply running at full load (which isn’t efficient for your rails, but we’ll get that later).  At 100W of use, your power supply is actually drawing 125W from your power grid.

80 Plus Efficiency Formula: PSU Wattage (100) / Efficiency (.80) = Power consumed (125w)


80 Plus is only the lowest acceptable rating you can get to be 80 plus certified.  There is also bronze, silver, gold, and platinum.  Additionally if you live somewhere where power into the house is brought in at 230V then there is also Titanium.  See the chart below for their efficiency at load.  When learning how to choose the right power supply for your PC this chart is the most important thing to know.


How to choose the right power supply for your PC

Chart found at : Wikipedia


Cost savings

Let’s quickly compare the cost savings of a 80 Plus power supply under 50% load versus a 80 Plus Platinum power supply under a 50% load.  We’ll be using 500W 24/7.  This may be unrealistic to some people, but for people folding or bitcoin mining, this is very realistic.

To calculate kWh (Kilo watts per hour), aka the method your electricity company uses to bill you, you take wattage consumed (500w) * time in use (24 hours) / 1000 (kilowatt hour).  That equals out to 12kWh, but we don’t have 100% efficient power supplies.  So 500W / .80 = 625 * 24 /1000 = 15kWh for our 80 plus power supply.  Let’s try out platinum rated power supply.  500w / .92 = 543.78 * 24 / 1000 =   13.04 kWh for our platinum rated power supply.

With my electric company, I pay .0596 per kWh.  So assuming I ran both power supplies for 30 days it would cost me $26.82 to run the 80 plus power supply, and $23.31 for the platinum rated.  I have a very low energy cost, so consider this as probably one of the lowest cost you’ll ever see.  If you live in a country outside the US, you’re likely paying much more per kWh.  Did you ever think knowing how to choose the right power supply for your pc could save you money on electricity?

Thermal transfer

So where did all that extra energy go?  It turned into heat, and once it turned into heat, your power supply fans kicked into hyper drive, the inside of your case rose in temperate, and now all your other components are needing to also increase their fan speeds to cool off.  So what’s our lesson here?  Don’t buy a cheap power supply; sacrifice the best GPU/CPU/Motherboard, whatever it may be to invest in a solid power supply.  If you asked anyone how to choose a power supply for your PC, I would bet they agree never to go cheap.

Not all power supplies are physically equal

A bad efficiency rating is not the only thermal issue.  Keep in mind the type of case you have, and the type of power supply you want.  Perhaps you have a mid-sized case, and go out and buy the first 80+ Platinum 1200W PSU you can find.  Well some power supplies actually come in smaller forms, to give you more space inside smaller cases.  If you have a full sized case, this probably won’t be an issue.  Just be sure you know how to choose the right power supply for your PC before you act on impulse.

Additionally, be conscious of where your power supply is going to sit.  If your case is only designed to mount the power supply at the bottom of the case, and doesn’t provide bottom vents, then you may have hot air circulating around your GPU.  Try to find something where the power supply intake is directed out of the case.  This cases the ambient air to go into the power supply, then exhaust out the back.

They also offer fan-less power supplies to eliminate noise issues, but keep in mind energy must be transferred.  So just because there is not a fan, does not mean the power supply isn’t generating some sort of heat inside your case.  With a fan-less power supply you sacrifice power, increase ambient temperatures, yet it makes a silent rig, making it ideal for HTPC use.

Cables and options

Traditional Power Supplies

To my knowledge there are two types of cable options for power supplies right now.  First, you have your standard power supply most of us grew up with, where the cables begin somewhere inside the power supply, and come out through a hole.  The image below is your typical non-modular power supply.  There are a few downsides to non-modular power supplies.  They can create the “spaghetti” effect inside your case with all the unused cables, which in turn blocks air flow inside your case.  On the other hand, they are much cheaper than modular power supplies.

How to choose the right power supply for your PC

Modular Power Supplies

Someone finally found a way to read minds, and must have heard me thinking one day.  I remember my days in electronic theory daydreaming about one day hacking my power supply and adding in molex connectors in the middle so I could remove unused cables.  Unfortunately I never acted on that thought, and about 7 years later someone else did.

If you ever used the old power supplies, you’ll understand the beauty of a modular power supply.  No longer do you have to fight a mess of cables.  Your temperatures in your case probably dropped due to less restricted air flow.  It’s just a beautiful thing, and I highly recommend getting one.  The only negative thing I can think of is the need to drag around a bag full of unused power cables and the cost.

How to choose the right power supply for your PC

Something much less important today, but may be important again some other day, so I will mention it now.  Make sure the power supply you are purchasing comes equipped with the power connectors you need.  Some Graphics Card’s use 2 8-Pin connectors, other use one 8 pin, and one 6 pin, then others use different variations of those.  Then there is always IDE & SATA, etc.  Just be sure your power supply has the power connectors you need.


Brand Quality & Under/Overpower


I’m going to wrap it up with a few important things that are important to any “how to choose the right power supply for your PC” type article.   First, buy a good quality brand named power supply.  Don not go cheap; do not buy a knock off no-name brand.  It might work for 10 years, or it might literally catch on fire and burn your house down.  Just spend the extra money and save your entire neighborhood from a blazing fire.

How to choose the right power supply for your PC


Earlier I mentioned you’ll need a little overhead when it comes to your wattage.  I have not been able to verify this personally, but I read numerous times that a power supply is most efficient when at 50% load.  Meaning, if you have a 1000w power supply, you want to be drawing 500w of power to achieve the highest level of efficiency.  This is not power efficiency from the wall but the quality of your 3.3v, 5v, and 12v rails.  That is more for the “how to choose the right power supply for your PC overclock edition”.  Maybe one day you will find yourself overclocking though!


The End.


That ladies and gentleman that is how to choose the right power supply for your PC.  Good luck on your journey!


Do you feel you know how to choose the right power supply for your PC?  Do you have any comments, or perhaps I left something out?  Let me know in the comments!

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