Check your power supply without opening the case

You can find your power supply's wattage and basic health information through Windows settings, the BIOS, or free third-party software — none of which require you to open the case. The easiest route depends on what you need to know: Windows shows you real-time power draw, the BIOS tells you the rated wattage if the manufacturer stored it there, and tools like CPU-Z or HWiNFO give you detailed voltage and temperature readings.

Most people need to check one of two things: whether their current power supply can handle a new graphics card or CPU, or whether their power supply is failing. The methods below handle both situations.

Key Takeaways

  • Windows Task Manager shows real-time GPU power draw under the Performance tab, which helps you see if your system is pushing close to your power supply's limit.
  • Your BIOS or UEFI firmware sometimes displays the power supply wattage during startup or in system information menus, though not all manufacturers include this.
  • Free tools like CPU-Z, HWiNFO, and GPU-Z display voltage rails, temperatures, and power consumption without requiring installation or case opening.
  • If your power supply is failing, you will see symptoms like random shutdowns, unexpected restarts, or fans spinning at full speed — software cannot always detect these, so physical inspection may be necessary.

Check power draw in Windows Task Manager

Open Task Manager by pressing Ctrl+Shift+Esc, then click the Performance tab. Select GPU (or whichever graphics processor you have) from the left sidebar. The GPU section shows real-time power consumption in watts at the bottom right of the window, labeled "Power (W)". This tells you how much power your graphics card is currently drawing.

For a more complete picture, check the CPU tab as well. CPU power draw appears in the same location. Add these two numbers together, then add roughly 50 to 100 watts for the rest of your system (motherboard, storage, fans, and other components). If that total is significantly lower than your power supply's rated wattage, you have headroom. If it is close to or exceeds your power supply's rating, you may be running too close to the limit.

Task Manager only shows what your system is drawing right now. To stress-test and see peak power draw, run a demanding game or use a tool like Prime95 (for CPU) or FurMark (for GPU) while watching Task Manager. Peak draw is what matters when deciding if an upgrade will fit.

Find your power supply wattage in BIOS or UEFI

Restart your computer and enter the BIOS or UEFI setup screen. The key to press appears on the startup screen — usually Delete, F2, F10, or F12, depending on your motherboard manufacturer. Once inside, look for a section called System Information, Hardware Information, or Main. Some boards display power supply wattage here; others do not.

Not all manufacturers store this information in the BIOS, so you may not find it. If you do not see it after checking the main sections, your motherboard simply does not report it. Exit the BIOS without saving changes by pressing Escape or selecting Exit Without Saving.

Use CPU-Z to check power supply information

Download CPU-Z from cpuid.com (the official site). Run the installer or portable version — no administrator rights required. Open CPU-Z and click the Tools menu at the top, then select "Integrated Devices" or look for a power supply section. Some versions of CPU-Z display power supply details here if your motherboard reports them.

If CPU-Z does not show power supply data, it means your motherboard does not expose that information to software. In that case, your best option is to look at the physical power supply itself — the wattage is printed on a label on the side or back of the unit. You can see this label without removing the power supply from the case in most builds.

Monitor voltages and temperatures with HWiNFO

Download HWiNFO from hwinfo.com and run the installer. Launch the program and select "Sensors-only" mode when prompted. HWiNFO displays real-time voltage readings for each rail of your power supply (12V, 5V, 3.3V), along with temperatures for your CPU and GPU.

Healthy voltages stay within these ranges: 12V rail between 11.4V and 12.6V, 5V rail between 4.75V and 5.25V, and 3.3V rail between 3.14V and 3.46V. If any rail is consistently outside these ranges, your power supply may be degrading. Temperatures above 50°C on the power supply itself (if your board reports it) suggest the unit is working hard or may be failing.

HWiNFO also logs data over time, so you can close it and reopen the log file later to see if voltages have drifted. This is useful for tracking whether a power supply is slowly failing.

Check GPU power with GPU-Z

Download GPU-Z from techpowerup.com. Run it and click the Sensors tab. GPU-Z shows your graphics card's power draw in real time, along with GPU temperature and clock speed. This is more detailed than Task Manager and updates more frequently.

Use GPU-Z while running a game or benchmark to see peak power draw. If your GPU alone is drawing more than half your power supply's rated wattage, you do not have much room for CPU power or upgrades. For example, if your power supply is 650W and your GPU draws 350W, you have only 300W left for everything else — which is tight.

Recognize signs of a failing power supply

Software can show you voltages and power draw, but it cannot always detect a failing power supply. Watch for these physical symptoms: random shutdowns or restarts with no error message, your PC shutting down under load but staying on during light use, fans inside the power supply spinning at full speed constantly, or a burning smell coming from the case.

If you see any of these signs, your power supply is likely failing and needs replacement — no amount of software monitoring will fix it. In this case, you may need to open the case or have a technician inspect the power supply physically. A failing power supply can damage other components, so do not ignore these warnings.

Frequently Asked Questions

How do I know if my power supply is strong enough for a new graphics card?

Check the graphics card's power requirements on the manufacturer's website, then use GPU-Z or Task Manager to see your current GPU power draw. Add the new card's power draw to your current CPU power draw (from Task Manager), then add 100 watts for the rest of your system. If that total is 80% or less of your power supply's wattage, you should be safe. For example, a 650W supply can handle a system drawing up to about 520W under load.

Why does my power supply wattage not show up in CPU-Z or BIOS?

Not all motherboards report power supply information to software. This is a limitation of the board, not the software. Your power supply's wattage is always printed on a label attached to the unit itself — look on the side or back of the power supply inside your case. You do not need to remove it to read the label.

What should my power supply voltages be?

The 12V rail should stay between 11.4V and 12.6V, the 5V rail between 4.75V and 5.25V, and the 3.3V rail between 3.14V and 3.46V. Check these in HWiNFO under normal use and under load. Small fluctuations are normal, but if any rail drifts outside these ranges consistently, your power supply is degrading.

Can software tell me if my power supply is about to fail?

Software can show you declining voltages or rising temperatures, which are warning signs, but it cannot predict failure. The most reliable indicators are physical symptoms: random shutdowns, constant fan noise, or burning smells. If you see these, replace the power supply — software monitoring cannot prevent damage once these symptoms appear.

Is it safe to run my PC at 90% of my power supply's rated wattage?

No. Power supplies are rated for continuous output, but running constantly at 90% of capacity shortens the unit's lifespan and leaves no headroom for power spikes. Aim to keep your peak power draw at 80% or less of your power supply's rating. A 650W supply should handle systems drawing no more than about 520W under full load.