How to Test Outlets For Power and Voltage

Proper electrical wiring is crucial for powering appliances and electronics safely in the home. An important part of maintaining a safe electrical system is testing outlets to ensure they are delivering the proper voltage and are grounded correctly. Testing outlets regularly can help identify potential wiring problems before they lead to dangerous situations like electrical fires or shock hazards. This comprehensive guide will provide an overview of how to thoroughly test electrical outlets for power and voltage.

Why Testing Outlets is Important

There are a few key reasons why it is important to test electrical outlets in your home:

  • Safety – Faulty wiring and outlets that are not properly grounded can present serious shock and fire hazards. Routinely testing outlets helps identify problems so they can be corrected before an accident occurs.
  • Performance – Outlets that deliver inadequate power or voltage can cause appliances and electronics to malfunction or fail prematurely. Testing ensures outlets are providing the expected 120 volts needed to operate equipment.
  • Preventative maintenance – Proactively testing outlets allows you to identify and address minor issues before they become larger problems. This prevents the need for costly repairs down the road.
  • New installations – Anytime new wiring or outlets are installed, they should be tested to verify proper operation and safety. Testing confirms everything was done correctly.

Taking the time to routinely test outlets provides peace of mind that your electrical system is functioning safely and properly for powering equipment.

What is Needed for Testing Outlets

Testing electrical outlets does not require much specialized equipment. Here are the basic tools needed:

  • Voltage tester – This is a pen-shaped device that lights up when detecting electric current. Used to confirm an outlet is live.
  • Multimeter – An electronic measuring instrument that can detect voltage, current, resistance, and continuity. Required for detailed voltage testing.
  • Outlet tester – A plug-in device that displays indicator lights revealing wiring faults like open grounds or reverse polarity.
  • GFCI outlet tester – Specialized tester just for GFCI outlets that trip the GFCI and confirm proper function.
  • Plug-in night light or lamp – Helpful for quick confirmation of live outlets during testing.
  • ** Phillips screwdriver** – For removing outlet covers and accessing wiring connections if needed.
  • Electrical tape – To safely cap wires when outlet is removed.
  • Camera – To take photos of the outlet wiring and connections for reference.

Having the right tools makes outlet testing much easier and provides more accurate results. The most essential are a non-contact voltage tester, a multimeter, and an outlet wiring tester.

Testing Outlet Voltage

The standard voltage of residential electrical outlets should be between 114 to 126 volts. Here are the steps for how to test an outlet for proper voltage:

1. Turn off power and remove outlet cover

Start by turning off the circuit breaker for the outlet at the main electrical panel. Remove the outlet cover plate so you can access the wires. Be sure to only work on one outlet at a time.

2. Confirm power is off

Before doing any work, reconfirm the power is off by using a non-contact voltage tester. Be sure to check both the hot and neutral terminals for any sign of voltage.

3. Connect multimeter leads

Set a multimeter to the AC voltage setting, usually marked with a V and squiggly line. Insert one probe from the multimeter into the hot slot of the outlet and the other into the neutral slot.

4. Restore power and take reading

With the leads in place, turn the circuit breaker back on. The multimeter will display the voltage reading for the outlet. It should be between 114 to 126 volts.

5. Test multiple outlets

For a more thorough test, repeat steps 1-4 to measure voltage on all other outlets along the same circuit to identify any inconsistencies.

6. Evaluate results

If voltage is outside the expected range, there may be a problem with the electrical wiring or service supply. Voltages over 126 or under 114 volts indicate issues that should be further investigated by an electrician.

7. Label problem outlets

Make note of any outlets with voltage readings outside the standard range so you can have an electrician repair them. Cover plates can be labeled or a warning sign posted.

Routinely testing outlet voltage helps confirm your electrical system is working properly for safely powering equipment throughout the home.

How to Test GFCI Outlets

GFCI outlets are an important electrical safety device, designed to immediately cut power if a ground fault is detected to prevent serious shock hazards. Here is how to properly test GFCI outlets:

1. Locate GFCI outlets

Walk around the house and take note of outlets marked “GFCI Protected” or with a “Test” and “Reset” button on them. Common GFCI outlet locations are bathrooms, kitchens, basements, garages, and exterior outlets.

2. Plug in GFCI tester

For outlets with “Test” and “Reset” buttons, plug in a GFCI outlet tester. Push the “Test” button on the outlet. This should trip the outlet and cause the indicator light on the tester to turn off.

3. Check function

If the GFCI outlets cut power to the tester when tripped, their ground fault protection is working properly. If not, the outlets could be improperly wired and may need replacement.

4. Reset outlet

Once testing is complete, press the “Reset” button to restore power to the outlet. Confirm the indicator light on the tester turns back on when reset.

5. Test downstream outlets

If one GFCI outlet controls others in a daisy chain setup, check that tripping the “test” outlet cuts power to those as well. Reset when done.

6. Verify frequently

GFCI outlets should be tested once a month to confirm the safety mechanisms are functioning as intended to prevent shocks.

Routinely verifying GFCI protection is a quick and easy way to help ensure your family’s electrical safety.

How to Test Standard Outlets

In addition to checking voltage and GFCI function, all standard outlets should also be tested for correct wiring and grounding. Here are the steps:

1. Get an outlet tester

Outlet testers are an inexpensive plug-in device that displays indicator lights revealing basic wiring issues. They are available at any hardware store.

2. Plug tester into outlet

With the power to the outlet on, simply insert the outlet tester. It will display a set of three lights providing details on the outlet’s wiring configuration.

3. Interpret indicator lights

Consult the user guide that accompanies the tester for specifics, but in general the lights can reveal:

  • Correct wiring if the top and bottom lights are on
  • Open neutral if only the bottom light is on
  • Open ground if the top light is off
  • Reversed polarity if the bottom light is off
  • General wiring faults if the middle light is on

4. Evaluate results

If anything other than the correct wiring lights are on, there is an issue with the outlet that needs to be repaired for safety. Consult an electrician immediately in these cases.

5. Test all outlets

For a thorough inspection, repeat the outlet tester process on every standard outlet in the home. Make notes on any problem wiring to be addressed.

Using an outlet tester at least annually provides inexpensive assurance that your home’s electrical outlets are wired safely and correctly.

What To Do If Outlet Problems Are Found

Finding a problem with your outlets when testing for power, voltage, or wiring faults indicates an electrical issue likely exists and should be addressed immediately for safety. Here is what to do next:

  • Evaluate scope of issue – Determine if the problem is isolated to just one outlet or if multiple outlets along the same circuit are impacted. This provides insight into the extent of the required repairs.
  • Label problem outlets – Clearly marking outlets that failed testing with electrical tape helps ensure everyone knows to avoid using them until they can be fixed.
  • Consult an electrician – Do not attempt DIY repairs unless you have electrical training. Contact a licensed electrician to fully evaluate problem outlets and conduct needed repairs.
  • Have electrician inspect full system – Beyond fixing the known issues uncovered, consider having the electrician complete a full inspection and test of the home’s electrical system for additional peace of mind.
  • Make repairs a priority – Faulty electrical wiring can quickly become a fire hazard. Schedule repairs as soon as possible once problems are identified.
  • Replace old outlets – If outlets are outdated or you are uncertain of their age, replacement with modern safety outlets may be the best solution.
  • Update electrical panel – For widespread outlet issues, having the electrical service panel inspected and potentially updated may provide a complete solution.

Responding quickly and bringing in professional expertise is important when outlet testing reveals electrical deficiencies that could put your home’s safety at risk if left unaddressed.

Safety Tips for Testing Electrical Outlets

It is important to exercise caution when testing outlets to ensure you do not get shocked. Here are some key safety tips:

  • Always turn off the power at the circuit breaker prior to beginning any testing.
  • Double check outlets for current with a non-contact voltage tester before touching wires.
  • Only work on one outlet at a time to avoid confusion.
  • Cap all exposed wires with electrical tape to prevent contact.
  • Wear rubber-soled shoes and avoid doing any testing standing on wet floors.
  • Do not put your fingers inside the outlet openings or touch wires when power is flowing.
  • When using a multimeter, ensure it is set to the proper range before taking measurements.
  • Only use tools with insulated grips designed for electrical work.
  • Never leave outlets uncovered or wires exposed when not actively working on them.
  • Replace outlet covers immediately once an outlet is tested before restoring power.

Exercising caution helps ensure you safely conduct outlet testing to uncover any potential electrical hazards without risk of shock or injury.

Frequently Asked Questions

How often should outlets be tested?

Electrical experts recommend testing all home outlets at minimum once per year. Testing twice a year is even better for identifying potential wiring faults as early as possible.

What tools are absolutely needed?

The two essential tools are a non-contact voltage tester to confirm power is off and a multimeter for checking outlet voltage. An outlet wiring tester is also highly recommended.

Do I need to shut off the main breaker?

Turning off the individual circuit breaker for each outlet is sufficient in most cases. Shutting off the main breaker can provide extra precaution when working with questionable wiring.

How long does outlet testing take?

Testing all outlets in a typical home can usually be accomplished in 30-45 minutes when equipped with the proper tools and following an organized room-by-room process.

What voltage is considered too high or low?

Standard voltage should be 114-126 volts. Voltages under 114 or over 126 volts often indicate problems and potential safety hazards with the electrical system.

Can I replace outlets myself?

If experienced with electrical work, you can replace outlets on your own. However, for issues uncovered during testing, it is best to have a professional electrician make repairs.

Why do outlet problems occur?

Reasons for outlet issues include loose connections, frayed wires, moisture corrosion, high-resistance points, overloaded circuits, and general wear-and-tear over time.

How much does outlet testing and repairs cost?

Electricians typically charge $50 to $100 per hour. Testing all home outlets averages 1-3 hours. Repair costs vary based on the specifics of the required work.


Routinely testing electrical outlets for proper power, voltage, and safe wiring is a simple way to help identify potential electrical problems before they result in dangerous mishaps or expensive damage. Investing a small amount of time using the proper outlet testing tools provides invaluable peace of mind that your home’s electrical system is functioning safely and properly. Be proactive in monitoring your home’s outlets and always enlist the services of a skilled electrician when issues are uncovered that require repairs beyond your expertise level. With periodic outlet testing and quick response to identified problems, you can take comfort knowing your home’s electrical system is safe and meets your family’s power needs.