GFCI Outlets Explained – The Un-Shocking Truth

Date Published: November 14, 2017

We’ve all seen those outlets with the little “test” and “reset” buttons on the face of the outlet.  These are called “GFCI” outlets.  The “GFCI” stands for Ground Fault Circuit Interrupter.   But what does that mean? And why are these types of outlets necessary?

The Shocking Details

Perhaps at some point in your life you have experienced a mild shock from an outlet while plugging in a cord. Or at some point in your childhood, you pushed something metallic into an outlet, possibly at a devious sibling’s prompting.

When this happens, the electricity travels quickly through your body, looking for a path to ground.  You essentially become the wire that the electricity travels through.  These types of shocks can be very jarring.

Thankfully, most of the time minor shocks don’t result in injury or death.  However, there is a real possibility that a person could suffer burns, tissue injury, or even heart failure and death from electric shock on a standard 120 volt circuit.

GFCI Outlet

There are various factors that can determine the outcome or severity of a shock.   These factors are:

  1. The strength of the voltage
  2. Your resistance as the conductor (wet skin is much less resistant than dry)
  3. The path that the electricity takes through your body (through the heart is a bad path)
  4. The duration of the electric shock.  If the amperage running through your body is high enough, your muscles can lose function or spasm, causing your body to freeze in place.  You may not be able to release your grasp on the item that is causing the shock.

It’s impossible to predict exactly how mild or severe an electrical shock will be, as these factors can come in a variety of combinations.  Contact with water is a key ingredient that should always be avoided, as it can cause you and your surroundings to become much more conductive.

But we can all agree that it’s best to try to avoid shock hazards entirely.

The Un-Shocking Solution

A GFCI outlet can greatly reduce this risk of life threatening electrical shock.  The GFCI outlet was designed with the sole purpose of protecting people from electrical shock.

This is completely different than the protection a breaker provides at an electrical panel: A breaker protects the structure from damage or fire.  The breaker will trip when too much current is running through a circuit, protecting the wiring from overheating.  But if you

are being shocked, the breaker may not trip quickly enough to save your life, or may not trip at all.

Enter the GFCI outlet, which is essential to protect people.  The GFCI outlet measures the amperage of the current flowing to and from the outlet.  If more power is going to the hot side of the outlet than is returning back through the neutral side, it will detect that difference, and interrupt the flow of electricity almost instantaneously.

This means that if you become a conductor for electricity to travel through your body, the outlet detects that less current is returning on the neutral side (because it is going through you), and it will shut off the power through the outlet within a fraction of a second.  This could very well save your life.  As explained earlier, when water is part of the equation, you can become a much better conductor, and the risk increases.

GFCI Outlet Example


This is why GFCI outlets have long been required on outlets or circuits that might be used near running or standing water, such as outdoors, at kitchens, bathrooms, garages, laundry rooms, etc.

Starting in 1968, the National Electrical Code (NEC) began mandating the use of GFCI Outlets in certain circumstances and areas.

The required locations for these outlets have gradually increased over the years, and typically have only applied to new construction and major renovations.

For more information, read the GFCI Fact Sheet from the Consumer Products Safety Commission.


Inspecting GFCI Outlets

During a home inspection, there is almost inevitably a conversation about GFCI outlets.   Our inspectors will note the presence or absence of GFCI outlets in the required locations.  We will alert you to these locations, so that you know where they are in case they were to trip. And we will test them when possible to verify that they are working properly.

There are many cases where we find that the GFCIs are not working properly, and would not actually provide any form of shock protection.  GFCI components can wear out over time.

Or they can be wired incorrectly in a manner in which the outlet works, but does not actually trip and shut off power. These are safety hazards that our inspectors will seek to bring to your attention.

On older homes, GFCIs may not be present, as they may not have been required by code at the time that the house was built.  If they aren’t present in your home, you ought to consider installing them.

GFCI outlets are relatively inexpensive, and a standard outlet can easily be swapped with a GFCI with minimal difficulty.  One GFCI outlet on the circuit can protect multiple outlets down-line, so you can often install just one on each required circuit, and the other outlets down-line on this circuit will be protected.

There are also circuit breakers with a GFCI and test button built in at the breaker, which can be used to provide this same protection for the entire circuit.

Test your GFCI’s Periodically

Because the internal components can wear out over time, you should also test these yourself on a regular basis.  This can be done by plugging in a simple appliance such as a lamp, and pressing the “test” button.

The outlet should make an audible click or pop, and the power to the lamp should shut off.  When the “reset” button is pressed again, the lamp should turn back on, as power is restored to the outlet.

If the outlet does not trip, or if it sounds as if it trips but the power remains on, or if it will not reset after tripping, the outlet is faulty or incorrectly wired. An electrician should investigate and repair or replace the GFCI as needed.

There is also a new product on the market that notifies you when a GFCI outlet is tripped. This can be useful if important items are plugged into GFCI outlets. Learn more about these here.

The ASHI Inspectors at Scott Home Inspection take safety concerns seriously – you should too.  Review where GFCI outlets need to be installed in your home and work with an electrician or qualified person to help update those outlets – your life may depend on it!  For more information on what is included in an ASHI Home Inspection, visit our Inspection Services page.

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About the Author: Luke Griess

Luke Griess is an ASHI certified Home Inspector and Certified HERS rater, with over 20 years cumulative experience in the home inspection, residential energy services, and construction industries.

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