Find your power supply wattage and model right now

Your computer's power supply is the box inside your case that converts wall power into the electricity your motherboard, graphics card, and drives actually use. You need to know its wattage (usually 450W to 1200W) and whether it works properly before you upgrade parts, troubleshoot a crash, or replace it. The fastest way is to open your case and read the label on the power supply itself—it lists the wattage in large print. If you cannot open the case or want to check without opening it, Windows and Mac both have built-in tools that show you what the system reports, though these are less reliable than the physical label.

Knowing your power supply matters because an undersized one will shut down your computer randomly during gaming or video editing, and an aging one can fail suddenly and damage other components. This guide walks you through three ways to find out what you have: reading the label directly, checking what your operating system reports, and understanding what the numbers mean.

Key Takeaways

  • The power supply label on the metal box inside your case shows the wattage, model number, and voltage—this is the most accurate information you can get.
  • Windows Task Manager and Mac System Information can show reported wattage, but they often underestimate what the power supply actually is rated for.
  • A power supply that is too weak for your parts will cause random shutdowns, especially during gaming or video editing when power draw spikes.
  • If your power supply is more than five to seven years old and you are upgrading to a new graphics card or processor, replacement is usually worth the cost.

Read the label on the power supply itself

The most reliable way to know your power supply is to look at it directly. Shut down your computer completely, unplug it from the wall, and wait 30 seconds. Open your case—most modern cases have a side panel held by two or four thumbscrews or a latch. The power supply is the large metal box, usually in the bottom rear corner. On one side of that box is a white or yellow label with black text. The wattage is printed prominently near the top—look for a number followed by "W" (watts). You will also see the model number, the manufacturer (Corsair, EVGA, Seasonic, and others), and input/output voltage specifications.

Write down the wattage and model number. If the label is faded or missing, the model number lets you search the manufacturer's website or a search engine to find the specifications. Keep the case open for now—you may want to check other details while you are in there. The label also shows the input voltage (usually 100–240V, meaning it works worldwide) and the amperage on each voltage rail, though you rarely need those details unless you are troubleshooting a specific problem.

Check what Windows reports about your power supply

If you cannot or do not want to open your case, Windows Task Manager can show you what the system thinks the power supply is. Open Task Manager (right-click the taskbar and select Task Manager, or press Ctrl+Shift+Esc). Click the Performance tab, then click CPU. At the bottom of the window, look for a line that says something like "Power usage" or "Power limit." This shows the current draw, not the total capacity—it will be much lower than your actual power supply wattage because your computer is idle.

For a more complete picture, use the System Information tool. Press Windows+R, type msinfo32, and press Enter. Look for "System Manufacturer" and "System Model"—if you bought a pre-built computer from Dell, HP, Lenovo, or another brand, you can search that model number on the manufacturer's support website, and they will list the power supply specifications. This method works well for laptops and pre-built desktops but is less useful for custom-built machines, where the power supply is not always documented in the system information. For custom builds, opening the case and reading the label is your best option.

Check Mac system information for power details

On a Mac, click the Apple menu, then select About This Mac. Click System Report. In the left sidebar, look for Power or Energy. The information shown here includes battery health (for laptops) and sometimes power adapter wattage, but it does not always list the internal power supply capacity for desktop Macs. If you have an iMac, Mac mini, or Mac Studio, Apple's support website for your specific model will list the power supply specifications.

For the most accurate information on any Mac, shut it down, unplug it, and open the case if possible. Mac power supplies are less accessible than PC power supplies—some are soldered to the logic board—so this may not be practical. In that case, search your Mac model number on Apple's official specifications page, or contact Apple Support with your serial number and they can tell you the exact power supply rating. Many Mac users never need to know this information because the power supply is not user-replaceable, but it matters if you are planning upgrades or troubleshooting stability issues.

Understand what the wattage number means

The wattage on your power supply label is the maximum continuous power it can deliver. A 650W power supply can safely run components that draw up to 650 watts under sustained load. Your actual power draw depends on what you are running—idle browsing uses 50 to 100W, gaming or video editing can spike to 300W or more, and a high-end graphics card alone can draw 250W to 450W.

A power supply that is too weak will shut down your computer when demand spikes, even if the average draw is lower. This is why a gaming PC with a high-end graphics card needs more headroom than a basic office machine. As a rule, your power supply should be at least 20 to 30 percent larger than your peak expected draw—so if your parts draw 500W under full load, a 650W supply is the minimum, and a 750W supply is safer. This headroom also extends the life of the power supply by keeping it from running at maximum capacity constantly.

Check if your power supply is failing

A power supply that is dying will show signs before it fails completely. Random shutdowns during gaming or video editing, especially when the computer is under load, often point to a power supply that cannot deliver stable voltage anymore. Unusual fan noise from inside the case—a loud whine or grinding sound—can mean the power supply fan is failing. A burning smell is a sign to shut down when ready and not use the computer until the power supply is replaced.

If your power supply is more than five to seven years old and you are planning to upgrade your graphics card or processor, replacement is usually worth doing preemptively. Power supplies degrade over time, and a weak supply can damage other components if it fails suddenly. A new power supply from a reputable brand (Corsair, EVGA, Seasonic, or similar) costs $60 to $150 for a mid-range unit and lasts 7 to 10 years. Replacing it before it fails is cheaper than replacing a motherboard or graphics card that was damaged by unstable power.

Know when to replace your power supply

You need a new power supply if the current one is failing (random shutdowns, noise, burning smell), if you are upgrading to parts that draw more power than your current supply can handle, or if it is very old and you are making a major upgrade. Before buying a replacement, write down the wattage you need based on your new parts, check the physical dimensions (some cases have space constraints), and verify that the connector type matches your motherboard—most modern boards use a 24-pin ATX connector, but older systems may use 20-pin connectors.

Installation is straightforward: shut down, unplug, open the case, disconnect the cables from your motherboard and drives, unbolt the old supply, slide in the new one, and reconnect the cables in the same order. If you are not comfortable opening your case, a computer repair shop can do this in under an hour for a reasonable fee. Make sure the new supply has the same form factor (ATX, SFX, or TFX) as your case—the label on your old supply will tell you which one you have.

Frequently Asked Questions

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

Search the model number (usually printed on the side or back) on the manufacturer's website or a search engine. If the label is completely gone and you cannot read the model number, you can estimate based on your case size and age—most standard cases from 2015 onward came with 500W to 650W supplies, while older cases often had 350W to 450W. A computer repair shop can also identify it for you.

Does a higher wattage power supply use more electricity?

No. A 750W power supply uses only as much power as your components draw—if your computer uses 300W, it uses 300W whether the supply is rated for 500W or 1000W. The wattage rating is the maximum it can deliver, not what it always draws. A larger supply may be slightly less efficient at very low loads, but the difference is negligible.

Can I use a power supply with lower wattage than recommended?

No. An undersized power supply will shut down your computer randomly when demand spikes, and it can damage your motherboard or graphics card over time by delivering unstable voltage. Always match or exceed the wattage your components need.

How do I know if my power supply is 80 Plus certified?

Look at the label on the power supply. 80 Plus certified supplies have a small 80 Plus logo (Bronze, Silver, Gold, or Platinum) printed on the label. This means the supply converts at least 80 percent of wall power into usable power, wasting less energy as heat. Certification is not required, but it is a sign of quality.

What is the difference between modular and non-modular power supplies?

A modular power supply has cables that plug in and out, so you only connect the ones you need. A non-modular supply has all cables permanently attached. Modular supplies are easier to install and keep your case cleaner, but they cost more. Both work equally well—the choice is about convenience and case airflow.