The Most Common Questions about Power Supply Units

This discussion has a more recent version.
edited September 2022 in Computer Hardware

Photos and writing by @Shoan041

What is a power supply?

 We’ve got an in-depth guide for all the power supply details, but the quick answer is that a power supply, or PSU, converts the energy from the outlet into a form that your computer can use. Basically, it’s what all the components need to function.

Do I need a new power supply for a new build?

 It is very common to need a new power supply with a new build. If this is your first build or a from-scratch build, then a PSU is an absolute necessity. If you’re building from an old PC and thinking about reusing your PSU, you might want to reconsider. If you have had a power surge or any electrical issues at all, I always recommend picking up a new power supply. Even if you haven’t had electrical issues, using a fresh power supply can help protect your components from failure.

Does the age of my power supply matter?

Old power supplies can cause issues with newer components. A power supply will lose maximum wattage and efficiency as the years pass. They have a lot of electricity going through them and they do wear out. Looking at the warranty on a power supply is a good rule of thumb for a power supply’s expected life span. The manufacturer tests their products for durability with moderate regular use to determine how long they expect it to last. An older, used power supply will not have the same performance as a new one and its performance will drop every year.

How do surges, blackouts, and brownouts affect my power supply?

Surges, blackouts, and brownouts are the bane of any electronic component, especially power supplies since they are the first components that an electrical current will go through and do their best to protect other computer parts. Surges in electricity will wreak havoc on electrical components, and the PSU is no exception.

A blackout is when there is an interruption in the electricity. It will cause your breaker switch to flip. That is a safety feature of a house in and of itself, but the electrical current can still cause problems and damage equipment. In this case, the power supply in a computer can be blown out and cease to function. 

A brownout is similar, but it isn’t enough to cause the breaker to flip off, but you can see its effects with lights dimming in the house. These are also very dangerous because they cause damage over time and shorten the lifespan of your devices, such as power supplies.

Yes, there are protections that you can buy, such as surge protectors or even better battery backups with AVR protection, but they can’t protect against everything all the time. I always use battery backups with AVR and surge protection on my computer, but I always keep in mind that those devices also wear out and can’t protect against higher voltage surges than what they are rated for. 

Can a faulty power supply damage other parts of my computer?

 I have seen many computer builders who attempted to use faulty power supplies and paid for it in the end. A power supply hit by a surge or too many brownouts can lead to damage for your other components. A power supply can surge other components when they die, causing those parts to malfunction or even fail. I always recommend buying a new power supply when you’ve had electrical issues and a fresh PSU for a new build is never a bad idea.

How much wattage does my power supply need?

It is very easy to calculate the wattage your computer is going to be using with a wattage calculator online, like the one on the Micro Center PC Builder. A power supply should be around twice the average amount of wattage your computer uses. This is because the power may spike to high wattages when under a heavy load. When power supplies are under a heavy load, they will be using more power. While you can use a power supply that is around what your PC “needs”, I don’t recommend it in most cases. When you have a power supply stressed to maximum wattage for long periods of time, it massively shortens the lifespan of the power supply.

Should I get a higher wattage power supply?

If you think you will want to upgrade to a better graphics card and/or a higher wattage CPU in the lifespan of your power supply, I would recommend going above and beyond to get a higher wattage PSU that can support the future parts. While it costs a little extra now, it will save you from having to buy a new power supply in the future with that upgraded graphics card or processor! While that might not seem like a big deal now, when you have to rewire your whole case for a new PSU, you’ll regret it.

Will a certain PSU fit in my case?

It is very important to check what size power supply your case will need. Most cases use a standard ATX power supply. Smaller cases, such as mini-ITX builds can use SFX power supplies instead. Check your case specs to make sure you’re getting the right power supply size!

What is power efficiency?

Power efficiency is how much energy is expended in order to achieve the desired result. So, the higher the percentage of efficiency, the less energy it expends to do the task. This is important, because that extra wasted energy is more heat that will be released into your case. More heat means your parts will die faster and they will be closer to thermal throttling! Both things you want to avoid as much as possible on your computer. Less wasted energy also means less electricity used and that means you will spend less on your power bill as well.

Does the 80 PLUS Certification rating really matter?

The 80 PLUS Certification is one of the most important aspects when considering your power supply. Better ratings mean better power efficiency leading to a cooler, potentially faster computer, that costs less electricity to run. Check our guide for a full explainer!

Can I get too high of a wattage power supply?

Yes, you can go too high in wattage! Power supplies have a bell curve of efficiency in which your energy will be most effective. Keep that in mind for both your current build and what you think you may need down the road.

What Cables do I need from a power supply?

Your 24-pin to the motherboard power cable is an absolute must, and you may need a number of 4+4 pin cables for your motherboard power, depending on your motherboard. SATA power is needed for most Solid State and Hard Disk Drives. Some add-on boards will use these as well. Most modern high-end Graphics Cards will require 1-to-3 6+2 pin cables directly to them. It is important to note that the 8 pin connectors are separated into 4+4 and 6+2 so that you don’t use the wrong one for the wrong job!

Why can't I just use a Y adapter to fit a power supply into a higher end graphics card?

Most decent power supplies come with all the cables they will realistically need. Just because you can buy a splitter for your 8 pin PCI-e cable for your new high-end GPU doesn’t mean you should! You still need a power supply that has the correct wattage to support that graphics card without damaging it.

Can I damage my components by plugging my power supply in incorrectly?

You can absolutely damage or destroy components that are not connected to power correctly. If you’re using the wrong cable, you might not have the correct wattage to run that part, leading to undervolting. Most modern power supplies can protect the GPU so it won’t get damaged from undervoltage, but I personally don’t recommend taking the risk! And if your cables are damaged, sparks could fly and, when a fire breaks out, a damaged computer is the least of your worries.

Should I unplug my power supply while working on my computer?

You should turn off and/or unplug your power supply when you are working on your computer. Accidentally turning it on when you don’t have it all put together could cause it to overheat or break. It’s also important to understand that turning it off isn’t the same as unplugging it. There is still electricity in the capacitors, keeping it from being shut off completely.

What is overvoltage protection?

Most good power supplies have some kind of overvoltage protection. As it sounds, it helps the power supply not get overvolted. This goes a long way to help it from taking other parts with it when it dies. Just keep in mind, it helps, but it can still happen!

Is it better to use separate cables for each PCIe connector?

Some power supplies come with a PCI-E 8-pin power that has two 8 pins on one cable. It is a good rule of thumb to avoid using this method when possible. It can cause the rail on the power supply to be overloaded with electricity or for it not be enough power to run the component. This is more of a generalization as different power supplies supply different cables. It's not a must, but a recommendation to be safe as opposed to sorry!

More from the Micro Center Community:

Looking for more information about Building a PC? We’ve got PC Build Guides as well as articles on How to Choose Parts for you Custom PC BuildProduct Reviews, and Part Comparisons. And if you can’t find what you’re looking for, don’t hesitate to post a new discussion and the Community will be happy to help!


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