Choosing a Computer Power Supply

steve Building a Computer , , ,

I know that this might not seem important, but choosing a computer power supply is extremely important for your computer build.

My brother didn’t know what he was doing when he built his first computer and got a power supply that was undersized. He ended up frying everything.

Messing this up can be a very costly mistake. This is one of those places where you don’t want to go cheap. But sometimes you can find a steal of a deal if you look around.

Power calculation

Every item on your computer uses electricity. I know you can call me Captain obvious now, but your power supply can only provide a finite amount of electricity.

In your house when you pull too much electricity your breaker will trip. In your computer there isn’t a breaker. If your computer pulls more than the power supply can provide, then you start to fry stuff.

The best thing to do to prevent this kind of catastrophe is to calculate how much power everything is going to pull, and double it. This will get you in a safe spot in case you forgot something or you decide to upgrade later down the road.

If you have a power supply that is rated much higher than what you actually need, then you computer just doesn’t pull Everything it can. For example, if your power supply is 1000w but your computer is only using 400w then you aren’t wasting 600 w. It just isn’t using it.

You don’t need to know how much electricity each part of your computer is going to use. Somebody else has already figured that out and had put together calculators. One of the ones I’ve used before can be found here.

When you use the calculator, it’ll give you a recommendation on how much you should

Bronze, Silver, Gold, and now Platinum

When you are looking at different power supplies you’ll notice that that some of them are bronze, silver, or gold certified.

This certification relates to how efficient the power supply is. When dealing with electricity, there are always heat losses. If you’ve ever touched an old incandescent light bulb you’ll know how much heat can be given off.

In a computer, heat is our enemy. If you can do something to produce less great it’s a pretty good idea to do it. Each of the different certifications is approximately 2% more efficient than the one before it.

They might save you money on your electric bill, but they’ll cost more out of pocket. There is a balance between between how much you pay now, and how much you’ll save on your electric bill.

When we did the power calculation I recommend that your power supply is able to produce twice as much power as you needed. Now you know why I recommended you to double it rather than just do a little better. You’ll acheive the best energy efficiency with 50% usage.

Cabels vs. Modular

Some power supplies are modular. All this means is that you can pick how many cables you plug into it. Like the one shown here.

If you get a non-modular power supply, then you’ll have to deal with storing the unused cables somewhere in your case.

This might not seem too terrible, but remember how I said heat was the enemy? Your case had fans on it to wake war against the heat generation. Cables are obstacles that block the cooling effects of the fans.

Some cables are simply necessary, and you’ll eventually need to figure out a way to deal with them… This means zip ties and a lot of them.

Cables that aren’t needed are just going to take up space and block your air flow. In my opinion getting a modular power supply is a much better approach.

Other Things to Consider

These are things that you probably aren’t going to need to worry about on your first power supply purchase.

There are different kinds of motherboards. The different boards have a different connector for the power cable. ATX is the standard, but you don’t want to make an assumption and then waste your money. You could potentuially have a an AT type motherboard.

There are single rail and multi rail power supplies. As long as you have a stable power source you will be good with a single rail. If you struggle with power outages or your power fluctuates then you’ll need a multi rail.

A power supply is a long term purchase. If you get a good one, you can expect to keep using it for 5 to 7 years! When you upgrade your system this little guy can still be used. If you do ever decide to upgrade your power supply, these things have a resale value.

Because a power supply doesn’t degrade over time, it holds it’s value at a descent rate and you can look at selling your old one on Craig’s List or a similar site.


THere are a good number of companies that make and sell power supplies, but not all of them have the same quality. Remember how I said this was super important? Getting this wrong can cause catastrophic issues with you computer.

Loyalty to certain brands is the norm for power supplies. My personal favorite is the Cool Masters, but Corsairs is also a good one.

As always, if you think I missed an important aspect, or just have any general questions, leave a comment below and I’ll be happy to offer assistance.


You May Also Like..

Liquid cooling vs fan cooling

In the world of computers, heat is the thing that causes the most issues. Consistently running while your computer is […]

How to Select A Video Card

Whether you’re building a new computer, upgrading your existing rig, trying to get into crypto mining,  or replacing a broken […]

How to Pick a Motherboard

So you have embarked on your journey to build a desktop computer. You should have an idea of the size […]


  1. I liked whatever you explained in there. Now I got some idea what to do with my computer power. I love working on computers. I had those type of ideas in mind but I wasn’t sure. Thanks for the experience.

    1. You’re welcome. The power supply is often forgotten about because it doesn’t add to the performance of the computer, but it plays a powerful role.

  2. Thank you for sharing the important information about power supply. I never thought too much about it before. This is really good to know.

    If I am building my computer from scratch and when I choose the motherboard that I want, does the motherboard manufacturer usually give me a recommendation on how much in Watt for my power supply that I will need? Do I also need to take the graphic card into consideration as well?

    1. Your manufacturer for the motherboard isn’t going to recommend anything in regards to your power supply. Everything you plug into your computer is going to increase the amount of electricity it takes. When you use the calculator, you’ll want to include your graphics card, processor, fans, RAM, hard drives, and even your mouse and keyboard.

      You never want to shoot for the minimum required for a power supply anyway. This way if you really have 7 fans in stead of 3 it’s not a big deal.

  3. Great post! I have been needing to upgrade my graphics card for a while but my current power supply wouldn’t hold up. I have never heard of a modular power supply before (honestly I never researched power supplies as much as I should). I’ll definitely be looking into one as I hate all the extra unused cables I’ve had in every pc I’ve had.

    1. Eventually, we all need to upgrade the power supply to keep up with other upgrades. Modular power supplies are my favorite. The come with all of the cables you’ll need you just get to pick which ones you use. Like everything else with computers, if the cable fits then that’s were it belongs.

Leave a Reply

Your email address will not be published. Required fields are marked *