You’ll need to open your computer and take a look. Unfortunately, there’s no way other than to look at your power supply to check what power supply you have. 

I’m Aaron. I’ve been tinkering with PCs for over 30 years. I believe that the best way to learn how to service a PC is to actively tinker with your PC. 

So roll up your sleeves and let’s dig into how you identify what power supply you have. 

Key Takeaways

  • Power supplies have a lot of important factors to consider.
  • If you want to know more about your power supply, read the manual. 
  • If you don’t have the manual or it’s not helpful, you’re going to need to open up your computer. 
  • If you don’t want to open your computer, then you may just have to accept that your power supply’s qualities will be a mystery. 

Why Does Power Supply Type Matter?

Power supplies are one of the most critical, but overlooked, parts of a computer. It provides the power by which your computer operates. While that may seem like a mundane proposition, it’s very important. 

Power supplies have a few different important identifiers.


Wattage is the amount of power that a power supply can deliver when under full load. You’ll want to oversupply wattage–not having enough power delivery can compromise performance or cause your computer to shut down. 


Power supplies will be rated with two efficiency indicators. The first is the 80 PLUS certification. 80 Plus means that the power supply is at least 80% efficient, meaning that only 20% or less of its power is converted to heat. 

Additional efficiency is demonstrated via metallic ratings: bronze, silver, gold, platinum, and titanium. Each of those ratings demonstrates additional power supply efficiency with less power converted to heat. 

Efficiency is important. The power supply sits in the same enclosed computer case as other heat-generating components: the processor (CPU), graphics processing unit (GPU), and hard drives or solid-state drives. The cooler those components, the better they typically perform. So if you’re looking for the highest performance, you’ll want the coolest power supply. 

Power Delivery Protection

Your power supply can be expensive but is far from the most expensive component in your computer. At the very least, your CPU, GPU, and motherboard are likely more expensive than your power supply. You want to protect those very sensitive components from potential overvoltage and other power-related events. 

Some power supplies will come with both Over Voltage Protection, or OVP, and short circuit protection. Other power supplies lack both. While it’s not common for a power supply to fry a computer, it’s certainly possible. 

Rails and Cables

Some power supplies use shared rails, or power delivery, circuits. Others have independent rails to deliver separate supplies of power to the motherboard and CPU, GPU, and drives. Depending on your performance objectives, you may want to look for one that provides different power rails to different components. 

Cabling is a related issue. Some power supplies are modular, or allow you to disconnect unused power cables. Others are non-modular and don’t allow that flexibility. 

Form Factor

Different power supplies have different form factors or shapes and sizes for different case needs. Most consumers will be using an ATX power supply and that’s the most common format sold. 

How Do I Check My Power Supply?

There are a couple of ways to check what power supply you have with one being much more complex than the other. I’ll start with the simpler one…

Read Your Computer Manual or Search the Internet

If you have your computer manual, that might tell you the computer specifications, including the specifications of your power supply. 

If you don’t have the computer manual, or if you do and it’s not particularly helpful, then search for it on the internet. Someone, somewhere, has likely chronicled the specific details of your computer. Those details may include information about your power supply. 

If they don’t…

You Open Your Computer

There are hundreds of different cases and I can’t cover every different layout. What I can do is generally describe how to open your computer case and where your power supply is likely located. 

Before you start, turn off your computer and unplug your power supply. Opening your computer with the power supply on and plugged in can result in damage to components or injury to you! 

The power supply cable will be a thick black cable, typically going into the top or bottom of your case. That’s because the power supply is usually found at the top or bottom of your case. 

Once you figure out where the power supply is, open the sides of your case. Typically that’s done by removing the large thumb screws at either side of your case. Thumb screws look like this:

Remove the sides of your case. I’m asking you to remove both because some cases mount the power supply to the left of the case. Some do to the right of the case. Since I don’t know the orientation of your case, I’m suggesting both. You can start with the left and then move to the right if you’d like. 

The power supply information should be printed on the side of the power supply. If you can only see one side of the power supply and can’t see the information, it might be on the obfuscated side of the power supply. 

At that point, your only option is to remove the power supply. At this point, you need to evaluate how important it is to figure out what power supply you have. 

Notably, if the computer is prebuilt (i.e.: it was built by a manufacturer and not by you or a specialized computer builder) then the power supply may not have consumer-identifiable information on it. 

If it’s very important to figure out what power supply you currently have, then you will need to remove it. Photograph or otherwise record how the power supply is plugged in. Then unplug everything. Unscrew the power supply from the back of the case and pull it out. 

If you have the information, great! If not, record any identifying information and search for it on the internet. After putting your power supply back into your computer, screwing it back into the case, and plugging everything back in, of course. 

You should now have successfully checked your power supply. 


Here are some common questions about checking your power supply. 

How do I Check My PSU Wattage Without Opening My Computer?

You can’t. Some sources suggest buying a watt meter to determine your power supply wattage. It’s unlikely you’ll ever run your computer at 100% of your power supply’s maximum capacity, so no matter what you measure you won’t know your power supply wattage without looking at it. 

However, by doing that, you can measure your computer wattage and make an educated guess about your power supply wattage.

How do I check my PSI Wattage in BIOS?

You can’t. Computer BIOS (actually UEFI for any computer made in the past 15 years) doesn’t read power supply wattage. They may read voltage off certain rails, but even that functionality isn’t uniform. 

How to Check Power Supply on PC Software

You can’t. You can read voltage on certain components, like the CPU and GPU. Different voltages are important because driving more voltage will help modify performance via overclocking or help diagnose performance problems. 

While wattage is the product of voltage times amperage (and amperage to PC components is constant) voltage has become the de facto standard for measuring modifiable power delivery to components, not wattage. That’s because voltage can be directly measured via a circuit, not wattage which has to be calculated. 


There’s a lot to think about when evaluating your power supply. How it’s built, how it delivers power, and how much power it delivers are key to determining your needs. While it could be easy to find that information, you may need to get your hands dirty and open up your computer. It’s a daunting proposition to do so, but as long as you handle your computer with care, you should be ok.

What was your first computer tinkering experience like? Let me know in the comments!