Where the power supply is located

Your computer's power supply is a metal box, usually rectangular, that sits inside your case and converts electricity from the wall outlet into the right voltage for your components. On a desktop computer, it is almost always in the bottom rear corner of the case — look at the back of your tower and you will see a metal box with a fan vent and a power cord plugged into it. On a laptop, there is no internal power supply; instead, you have an external power adapter (the brick) that connects to your laptop with a cable.

If you open your desktop case, the power supply will be the heaviest metal component you see. It has thick cables running from it to your motherboard, graphics card, and storage drives. Do not touch the inside of the power supply itself — the capacitors inside hold a charge even when unplugged, and opening it is dangerous.

Key Takeaways

  • Desktop power supplies sit in the bottom rear corner of the case and have a fan vent and power cord visible from the back.
  • The wattage rating is printed on a label on the side or back of the power supply unit itself, not in your computer's settings.
  • You can also find power supply information in your motherboard manual or by checking the manufacturer's website with your computer model number.
  • Laptops do not have internal power supplies; the external adapter brick shows the wattage and voltage on its label.
  • Never open a power supply unit yourself — the internal components can hold a dangerous charge even when unplugged.

Reading the label on the power supply

The easiest way to find your power supply's specifications is to read the label stuck to the unit itself. On a desktop, you will need to look at the back or side of the metal box. The label lists the wattage (usually 500W, 650W, 750W, or higher), the voltage it accepts, and the manufacturer's name. Write down the wattage — this is the number you need if you ever have to replace it.

On a laptop, the external power adapter has a label on the bottom or side. It will show the wattage output (often 65W, 90W, or 140W depending on the model) and the voltage. This label is much easier to read than on a desktop because you do not have to open the case.

Finding power supply info in your computer's settings

Windows and Mac do not display power supply wattage in their system settings — the operating system does not track this information. However, you can find the model number of your computer, and then look up the power supply that came with it from the manufacturer.

On Windows, go to Settings > System > About and note your computer model number. On a Mac, click the Apple menu > About This Mac. Then visit the manufacturer's website (Dell, HP, Lenovo, Apple, etc.) and search for your exact model number. The specifications page will list the power supply wattage that shipped with that model. Keep in mind that if someone replaced the power supply before you bought the computer, the original spec may not match what is actually inside.

Checking your motherboard manual

If you have the manual that came with your computer or motherboard, it will list the recommended power supply wattage. For a desktop, the motherboard manual is often the easiest reference because it tells you the minimum and recommended wattage for that specific board. You can usually read the manual as a PDF from the motherboard manufacturer's website if you have the model number.

The model number is printed on the motherboard itself, usually near the CPU socket or along an edge. Once you have the model number, search for "[Model Number] manual" and read the PDF from the manufacturer — ASUS, Gigabyte, MSI, and other makers all host these for free. The power specifications section will tell you what power supply that board expects.

Identifying power supply problems

If your computer shuts down randomly, restarts without warning, or fails to turn on, the power supply may be failing. A failing power supply often makes a buzzing or humming noise that is louder than normal fan noise. You might also smell a burnt plastic odor coming from the back of the case.

If you suspect a power supply problem, do not open the case yourself. Shut down the computer, unplug it from the wall, and wait at least five minutes before touching anything inside. If the problem persists, take the computer to a repair shop — they have the tools to test the power supply safely and replace it if needed.

Understanding power supply wattage

The wattage number on your power supply tells you the maximum power it can deliver to your components. A 650W power supply can deliver up to 650 watts; a 1000W supply can deliver up to 1000 watts. Your actual usage is usually lower — a typical gaming desktop might use 400 to 600 watts under full load, while an office computer uses 150 to 300 watts.

If you are upgrading your graphics card or adding new components, you need to make sure your power supply has enough headroom. A good rule is to choose a power supply rated for at least 1.25 times your estimated peak usage. If your new graphics card and CPU together draw 500 watts, a 650W supply gives you a safe margin. If you are unsure whether your current supply is enough, a repair technician or the graphics card manufacturer can tell you what minimum wattage they recommend.

Finding the serial number and manufacturer

The label on your power supply also shows the manufacturer's name and a serial number. Common power supply makers include Corsair, EVGA, Seasonic, and Thermaltake, though many computer manufacturers (Dell, HP, Lenovo) use their own branded supplies made by other companies. The serial number is useful if you need to contact the manufacturer about a warranty claim or recall.

If the label is worn or unreadable, you can sometimes find the manufacturer's name printed on the fan cover or the metal casing. If you still cannot read it, take a photo of the power supply from multiple angles and bring it to a repair shop — they can usually identify it by sight.

Frequently Asked Questions

Can I check my power supply wattage without opening the case?

Yes. Look at the back of your desktop case where the power cord plugs in — the label is often visible from outside. If not, you can find the wattage by looking up your computer model on the manufacturer's website. For laptops, the wattage is printed on the external adapter.

What if I cannot read the label on my power supply?

Take a clear photo of the label from different angles and bring it to a computer repair shop. They can identify the manufacturer and wattage from the photo. Alternatively, look up your computer model number on the manufacturer's website — the specs page will tell you what power supply came with it.

Is it safe to open my computer case to see the power supply?

It is safe to open the case and look at the power supply label, but do not touch the power supply itself or unplug any cables while the computer is on. Always shut down and unplug the computer from the wall first, then wait a few minutes before opening the case.

How do I know if my power supply is failing?

Signs include random shutdowns, unexpected restarts, failure to turn on, buzzing or humming noises, or a burnt plastic smell from the back of the case. If you notice these symptoms, shut down the computer, unplug it, and take it to a repair shop for testing.

What wattage power supply do I need for my computer?

This depends on your components. Check your graphics card and CPU manufacturer's recommended wattage, then add a safety margin of about 25 percent. A repair technician or the component maker can tell you the minimum wattage needed for your specific setup.