Testing Electrical Outlets With a Voltage Tester and Other Methods

  • 01 of 04

    Is That Outlet or Light Powered Up?

    Young woman checking socket with multimeter
    Ulrike Schmitt-Hartmann / Getty Images

    Determining whether a household circuit is powered, live, and hot can be as simple or as complicated as you like.  Methods range from easy and free (a working lamp) to an over $700 device that uses radar waves.

    Prior to performing any electrical work, four methods can help you figure out if that outlet or light box has power running toward or through it.

    If you have any reservations about working with household current, call an electrician.  While electrical is one of the more expensive trades to...MORE call to your house, it is far cheaper than a trip to the emergency room (or worse).

    1.  Plugging In a Working Light

    Bottom Line:  Fine for testing one or two outlets, but not much else.

    This classic method of testing for power could not be simpler.  If current is running to an outlet, then it will power a light.  

    There is no reason why you cannot use this to test the occasional outlet.  But if you plan to do any amount of DIY electrical work, you should buy a voltage tester.

    2.  Using a Voltage Tester

    Bottom Line:  Cheap and easy to use, a voltage tester represents the "sweet spot" in electrical testing tools for do-it-yourselfers.

    A voltage tester is a lifesaver.  Unlike other helpful, time-saving home remodeling-related gadgets that we like to call lifesavers, electrical voltage testers literally aid in the prevention of injury or death from accidental electric shock. 

    Inexpensive (under $15) and reliable voltage testers like the Klein NCVT can detect electrical current without touching the exposed wires.  Hover the tip of the voltage tester about one inch from the wire, and the tester will chirp and flash a light if current is detected.

    One downside of these pen-style voltage testers is that they cannot detect current in low voltage devices, like pathway lights or small home appliances.  For that, you need a multimeter.

    Do not confuse with a voltage meter, which indicates the precise voltage of electricity. A voltage test is an on/off tool. "On" means that there is electricity; "off" means there is none.

    Items of caution with voltage testers:

    • If batteries fail, it may appear that current is dead even if it is not. Note: always test the voltage-tester before using it.
    • Even if the batteries are good, these items are notorious for providing false-positives and false-negatives.  A false-positive is when the tester beeps, but there is no current.  Of greater concern is the false-negative, when it doesn't beep even though current is flowing.


    Buy on Amazon - Klein Tools Dual Range Non-Contact Voltage Tester

    3.  Using a Multimeter

    Bottom Line:  Highly accurate, multimeters are overkill for most home electrical use by DIYers.

    A voltage tester is a simple "yes or no" device.  It detects whether the current fully dead or highly powered.  When you touch a voltage tester to a live low-voltage wire, it will register that wire as dead.

    For these lower voltages and for determining what that voltage is, you need a multimeter.  

    4.  Using a UWB Device

    Bottom Line:  The only device that will detect live wires behind drywall.

    Ultra-wide band radar devices like the Bosch D-Tect are not used for normal detection of live currents, such as mentioned above.  However, it is the only tool available on the consumer market that will detect powered-up, live electrical cables behind drywall--without tearing out the drywall.



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  • 02 of 04

    Test Out the Voltage Tester

    Photo © Lee Wallender, licensed to About.com

    Find an electrical receptacle that you positively know is live. Typically, this is a receptacle that is powering an appliance, radio, TV, computer, etc.  Make sure that the outlet is powering the device by turning it on.

    Be sure to check both the top and bottom portions of the outlet. 

    Insert end of voltage tester in both slots of the live receptacle. Depending on your model, the tester should flash, beep, or both flash and beep if the current is live.

    The reason for this step is that you want to...MORE make certain that the voltage tester is working. Dead batteries in the voltage tester may give the impression that a receptacle is safe to work on, even if it is not.



    Continue to 3 of 4 below.
  • 03 of 04

    Test Intended Receptacle

    Photo © Lee Wallender, licensed to About.com

    Insert end of voltage tester into both slots of receptacle. A flashing light or beep indicates if the current is live.

    As an additional precaution, after you open up the receptacle to work on it, you should once again test the wires inside of the box. 

    Black wire casing usually indicates that this wire carries an electrical load when powered up.  Test these black wires and all other wires inside of the box.

    Continue to 4 of 4 below.
  • 04 of 04

    Voltage Tester May Also Be Used to Test Electrical Cords

    Photo © Lee Wallender, licensed to About.com

    Hold tip of voltage tester against side of electrical cord. Be certain to touch all the way around the cord. Three major wires--positive, neutral, and ground--run through most electrical cords. Tester indicates live current only when it is against the positive wire.