When building or upgrading a PC, many people focus on flashy parts like graphics cards or RGB lights. But one of the most important parts of your computer is something you might not even notice—the power supply unit (PSU). It’s the piece that makes sure every other part of your PC gets the power it needs to run smoothly and safely.
In this easy-to-follow guide, you’ll learn:
- How to check what power supply you have
- How to test a power supply
- How much power supply you need
- When to upgrade your PSU
Let’s break it down step-by-step, so even if you’re new to PCs or in 8th grade, you’ll totally get it.
Why Your Power Supply Matters
Think of your PSU like the heart of your PC. Without it, nothing works. If your power supply doesn’t give the right amount of power or if it fails, your whole system could:
- Shut off randomly
- Crash during games
- Get damaged from overheating or voltage spikes
Not only does it power your PC safely, but a good PSU:
- Helps your PC run smoother and quieter
- Uses less electricity (saves money!)
- Gives you room to upgrade later
So even though it may not be flashy, your power supply is super important.
How to Check What Power Supply You Have
You can’t use a program on your PC to find out which PSU you have—you’ll need to look for it yourself.
Option 1: Open Your PC and Read the Label
- Turn off and unplug your PC.
- Open the side panel of your case.
- Look for a sticker or label on the power supply.
What you’ll find:
- Brand and model (like Corsair RM750x)
- Wattage (like 500W, 650W, 750W, etc.)
- 80 PLUS rating (tells you efficiency)
- Info about power rails (don’t worry—just take note of it)
📸 Tip: Take a picture of the label so you don’t forget!
Option 2: Check Paperwork or Manufacturer’s Website
If your computer is prebuilt (like from Dell or HP), check your receipt or search your model online—sometimes PSU info is available there.
Option 3: PSU Monitoring Tools (Limited Info)
Some tools like HWiNFO show voltage numbers, but they can’t tell you the make or model of your PSU.
How to Test PC Power Supply
If your computer has been acting weird—like crashing, restarting randomly, or won’t turn on—it might be your PSU.
Here are 3 ways to test it:
- Use a PSU Tester (Most Reliable Way)
A PSU tester is a small, cheap tool you can buy online.
How to use:
- Unplug PSU from PC parts
- Plug the 24-pin connector (the big one) into the tester
- Flip on the PSU switch
- The tester will light up and show voltage numbers
Make sure the voltage numbers are close to these:
- 12V rail: 11.4V to 12.6V
- 5V rail: 4.75V to 5.25V
- 3.3V rail: 3.14V to 3.47V
If they’re way off, your PSU may be broken.
- Paperclip Test (For Advanced Users)
This is a “quick and dirty” way to see if the PSU turns on at all.
How to do it:
- Unplug PSU from everything
- Unclip the 24-pin cable
- Use a paperclip to connect the green wire and any black wire
- Plug in and turn on the PSU
- If the fan spins, it turns on (but this doesn’t show if it works under pressure)
⚠️ Warning: Be careful doing this! Only try this if you’re confident and know what you’re doing.
- Software Monitoring (If Your PC Still Turns On)
If your PC is running, you can use free software like HWiNFO or Open Hardware Monitor to watch your voltage numbers.
Watch for:
- Big drops or spikes in the 12V or 5V lines
- Changes during gaming or heavy use
This won’t tell you everything, but it can give hints.
How Much Power Supply Do I Need?
This is one of the most common questions when building a new PC.
Your power supply needs to power everything in your case, including:
- CPU and GPU (these are the biggest power users)
- Hard drives and SSDs
- Fans and coolers
- Lights, USB devices, etc.
Use a Power Supply Calculator
Go to a site like https://www.coolermaster.com/en-in/power-supply-calculator/ and type in:
- Your processor (CPU)
- Graphics card (GPU)
- Drives and extras
It will tell you how many watts you need.
Example Build:
- Intel Core i7-13700K
- NVIDIA RTX 4070 Ti
- 1 SSD, 1 HDD
- 4 fans
Recommended PSU: At least 750 watts (Gold-rated if possible)
Tip: Add 100–150W more than you need, just in case you upgrade later.
Understanding 80 PLUS Ratings
The “80 PLUS” rating tells you how efficient a PSU is.
Here’s what they mean:
- Bronze: at least 82% efficient
- Gold: around 87–90% efficient
- Platinum: over 90% efficient
More efficient = Cooler, quieter, and cheaper to run long-term.
When Should You Upgrade Your Power Supply?
If your current PSU is too weak for your new parts, or it’s getting old, it might be time to upgrade.
Signs You Need a New PSU:
- You upgraded your GPU or CPU, and the PSU can’t handle it
- PC crashes or shuts down while gaming
- Your PSU doesn’t have the right connectors (like for modern GPUs)
- It makes weird noise or runs hot
- It’s over 5 years old (especially if it’s a cheaper unit)
Match the PSU to Your Build
Make sure your new PSU:
- Fits your case (ATX for full-size, SFX for small cases)
- Has all the cables you need (24-pin, 8-pin CPU, PCIe cables)
- Comes from a trusted brand
Top PSU Brands to Look For:
- Corsair
- Seasonic
- EVGA
- be quiet!
- ASUS ROG (premium, for gamers)
Modular vs Non-Modular PSUs: What’s the Difference?
All power supplies come with cables—but how they connect matters for cable cleanup and airflow.
- Non-Modular: All cables are fixed. It’s cheap but messy.
- Semi-Modular: Main cables attached, the rest are optional.
- Fully Modular: All cables can be plugged in or removed. Best for clean builds.
👍 My advice: Go fully modular if your budget allows—it makes your build look and feel much better.
Conclusion: Know Your Power, Power Your PC
Your power supply may not be the most exciting part of your PC, but it’s one of the most important! Knowing how to check what power supply you have, how to test PC power supplies, and how much power supply you need can help you avoid future problems.
Here’s what we learned:
- Always check your PSU label to know what you have
- Test your PSU if your PC crashes or doesn’t turn on
- Use a PSU calculator to know how much power you need
- Upgrade if your PSU is too old or too weak for your parts
When in doubt, choose a good brand, leave some headroom, and don’t cheap out—your entire system depends on your PSU doing its job right.
Happy building! 💻⚡