How to Test PC Power Supply (PSU) with 3 Methods

Power Supply, or Power Supply Unit  (PSU), is the core internal hardware of a PC for electricity. A PC cannot run without power supply.

The fact is that you cannot get any information about the PSU (its model, total wattage, or others) in system information. The fastest way is to check the label attached on your PSU after turning off your PC and open the case. Or go to the manufacturer's official support to get detailed information.

Test your Power Supply Unit (PSU) to verify if it delivers stable, clean, and sufficient power to your hardware or not. If there is any issue for PSU, it may trigger unexpected shutdowns or cause permanent damage to connected components. So test your PSU is necessary especially for the following situations:

• No power at all: Your PC cannot turn on.

• Sudden shutdowns under load: Your PC turns off instantly without a Windows "shutting down" screen when launching games or heavy rendering tasks.

• Random restarts & BSODs: You experience frequent Blue Screens of Death or system freezes.

• Strange physical signs: Encounter persistent burning smell, high-pitched electrical noise.

• Before upgrading CPU or GPU: Ensure your current PSU can handle transient power spikes for new higher-wattage graphics card or processor.

• Before installing a second-hand PSU: Test with a paperclip or digital PSU tester.

Method 1. Test PSU with Paperclip

Use a paperclip to test if your PSU can power on or not.

Step 1. Prepare a metal paperclip and bend it into a U-shape.

Step 2. Locate pin 16 and pin 17 on the 24-pin cable and insert the ends of the paperclip into pin 16 and pin 17. (To find pin 16 and pin 17, let the clip face up and the pins face toward you, count from left to right and the 4th and 5th pins are what you need. )

Step 3. Turn on the PSU.

Step 4. If the PSU fan spins up, the PSU functions normally.

Method 2: Use Multimeter for Precision Measurement

Use a multimeter to manually verify rail voltages while the PSU is jumped via the paperclip method.

1. Set up a multimeter dial to DC voltage.

2. Insert the black multimeter probe into any Ground terminal on the 24-pin connector or a Molex connector.

3. Test voltage rails by touching a red probe to terminals inside the 24-pin connector.

Method 3: Digital PSU Tester

Use a dedicated tester to get immediate, accurate LCD voltage readings across all rails.

1. Disconnect AC power.

2. Plug the 24-pin ATX cable into the tester to build connection. Attach additional CPU (4/8-pin) , PCIe (6/8-pin), and SATA connectors to test each output rail.

3. Plug in the AC cord and switch the PSU on. You can get the active voltages and PG delay on the LCD panel.

4. Compare the values with safe ATX specifications:

• +12V Rail: 11.4V - 12.6V

• +5V Rail: 4.75V - 5.25V

• +3.3V Rail: 3.135V-3.465V

• PG Value: 100ms-500ms

Using a Power Supply Unit (PSU) calculator provides an accurate estimate of your system's peak power demands. After getting the recommended wattage, you should buy one that is higher so your PC's normal peak power consumption sits between 50% and 80% of the PSU's total capability.

Here we take IObit Power Supply Calculator as an example to show how to test PSU wattage.

Step 1. Go to the IObit Power Supply Calculator page.

Step 2. Input detailed information about your PC, including the following:

• CPU (brand, socket, model)

• GPU (brand, graphics card, quantity)

• Motherboard (option)

• Memory module, SSD type, and HDD RMP & size (optional)

Step 3. Click the Calculate Now button to get the recommended PSU wattage.

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