How to Use a Voltage Tester to Check If Power Is Off

Be sure you've properly turned off the power before you begin any electrical project. Here's how to use a voltage tester during home repairs.

voltage tester on tile

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Project Overview
  • Working Time: 30 minutes
  • Total Time: 1 hour
  • Skill Level: Beginner
  • Estimated Cost: $10 to $25

A voltage tester is designed to test for the presence of an electrical current. It is different from a multimeter, which can perform the same basic test, but also measures the voltage, current, resistance, and more. Both devices are useful for home electrical system repairs, and they function essentially the same. However, a multimeter requires more preparation to connect the multimeter leads to the correct jacks, select between testing AC or DC current, and to move the rotary dial to the appropriate setting for the desired test.

This added complexity is more than you need if you are just testing an outlet, light switch, wires, or even a battery for an electric current. A simple voltage tester is more affordable and easier to use. Use this guide to learn how to use a voltage tester to check if power is off before starting an electrical project.

Safety Considerations

Whenever you are dealing with the home electrical system it's important to proceed with caution to help avoid accidental electrocution. A voltage tester is one tool that can help keep you safe while you work on the electrical system, but it's necessary to note that a voltage tester can give a false reading. If the batteries are dying or the voltage tester is faulty, it may beep or vibrate while testing a dead circuit.

However, the real risk is if the voltage tester doesn't beep or vibrate while testing a live circuit. For this reason, it's recommended to test the voltage tester before every use. Additionally, it's a good idea to wear insulated gloves that can help protect you from electric shock.

Before You Begin

Receiving a false positive on a dead circuit can be annoying, but isn't as dangerous as receiving a false negative when the circuit is still live. Before using the voltage tester on a circuit, outlet, or light switch that appears dead, test the voltage tester on an outlet that you know is live to ensure that the voltage tester is functioning properly. Typically, this is a receptacle that is already verifiably powering a lamp, microwave, radio, TV, or computer.

Turn the connected device on to ensure that the outlet is live and powering the device. After this quick check, turn the device off and use the voltage tester to check the outlet for an electrical current. The tester should flash, beep, or both flash and beep to indicate that the outlet is live. If the tester does not respond, then the batteries may need to be changed or the voltage tester may be faulty.

There are three main types of voltage testers. The most common option is a contact voltage tester, which uses two metal probes to test the flow of electricity. There are also non-contact voltage testers which can detect an electrical current from about an inch away, instead of coming into direct contact with the outlet or exposed wiring. A third type of voltage tester, called a receptacle tester, is made for testing outlets. This device plugs directly into a three prong outlet to provide information about the electrical current.

What You'll Need

Equipment / Tools

  • Voltage Tester
  • Screwdriver
  • Insulated Gloves


  • Batteries


How to Use a Voltage Tester to Check if the Power Is Off

  1. Set-Up the Voltage Tester

    Put new batteries into the voltage tester and verify that they are facing the correct direction before closing the battery compartment. Turn the voltage tester on and use it on an outlet that you know is live to ensure the voltage tester is working.

  2. Test an Outlet

    To test an electrical outlet with a contact voltage tester, insert each probe into the slots of the outlet. If the outlet is live, the voltage tester should beep, flash, vibrate, or some combination of the three, depending on the specific product.

    Use a receptacle voltage tester by plugging the device into the outlet. The lights on the device will come on to indicate the presence of a live electrical current.

    Test an electrical outlet with a non-contact voltage tester by holding the tester about an inch away from the short slot on the outlet. This slot is considered the hot slot, while the long slot is the neutral slot. If the outlet is live, the voltage tester will beep or flash.

  3. Test the Wiring

    The indicator on the voltage tester can vary depending on the product. Look out for a beep, flash, or vibration when using the device.

    Test wiring with a contact voltage tester by touching the probes to the hot and neutral wires. Similarly, you can test wiring with a non-contact voltage tester by holding the tester about an inch away from the hot wire. However, receptacle testers are not suited for this purpose.

  4. Test Batteries

    Testing old batteries is another use for a voltage tester. While it may not seem worthwhile to do this with small, disposable batteries, testing a car battery can help to diagnose a problem with the vehicle.

    Use a contact voltage tester to determine if a battery is dead or live. Place one probe on the negative terminal, which is typically labeled with a minus sign. Place the other probe on the positive terminal, marker with a plus sign. If the voltage tester beeps, vibrates, or lights up, then the battery is live.

    However, it should be noted that a multimeter is the better option for this task. This is because the multimeter can determine the voltage across the battery. Ideally, the voltage should be between 12.6 to 12.8 volts.

  5. Test a Light Switch

    Testing a light switch is similar to testing an outlet. Start by unscrewing the faceplate from the wall. Touch the probes on a contact voltage tester to the screw terminals on the side of the light switch to detect a live current.

    You can also use a non-contact voltage tester by holding the tester about an inch away from the screw terminals to detect an electrical current. When you're done, secure the faceplate to protect the electrical components of the switch.

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