GFCI and AFCI protection explained

GFCI and AFCI are two kinds of electrical protection that sound alike but do different jobs. A GFCI protects people from shock. An AFCI protects the house from fires that start in the wiring. Newer homes have both in specific rooms. Many older homes have neither, or only some, because the rules came in over several decades.

The short version

	GFCI	AFCI
Stands for	Ground-fault circuit interrupter	Arc-fault circuit interrupter
Protects against	Electric shock and electrocution	Fires caused by arcing in wires and connections
What it watches for	Electricity leaking out of the circuit, for example through a person	Sparking (arcing) from damaged, loose or overheated wiring
Where you find it	Usually an outlet with "Test" and "Reset" buttons, or a breaker in the panel	Usually a breaker in the panel with a test button; some are outlets
Typical rooms	Bathrooms, kitchens, garages, outdoors, basements, laundry areas	Bedrooms and, in newer homes, most living areas

What a GFCI does

A GFCI constantly measures the current going out on a circuit and coming back. If some current is leaking out, for example through a person touching a faulty appliance near a sink, it shuts the power off in a fraction of a second [1].

The Consumer Product Safety Commission (CPSC) describes three types [1]:

GFCI outlet. Replaces a standard outlet. It protects whatever is plugged into it and can also protect other outlets wired after it on the same circuit.
GFCI breaker. Installed in the panel. It protects every outlet, light and appliance on that circuit.
Portable GFCI. Plugs into an outlet, or is built into an extension cord, for places where an installed GFCI isn't practical.

What an AFCI does

An arc is electricity jumping a gap, like a spark. Arcs happen when wires or cords are damaged, overheated or stressed, or when a connection works loose. An AFCI detects dangerous arcing and shuts off the power before a fire can start [3]. Without one, the CPSC says this kind of arcing can cause unnoticed overheating and start a fire [2].

A standard breaker trips when a circuit draws too much current. It isn't designed to catch arcing. AFCI breakers replace standard breakers in the panel and protect the whole circuit [3]. Some manufacturers also make "dual function" devices that combine AFCI and GFCI protection in one breaker or outlet [6].

Where homes usually need them

Both are set by the National Electrical Code (NEC), which is updated every three years. The NEC typically applies to new construction and major renovations, not to existing homes [1]. That is why a home usually has the protection that was required when it was built or last rewired.

GFCI requirements came in room by room. The CPSC lists when the NEC first required GFCI protection for outlets in each area [1]:

Area	First required
Outdoor outlets	1973
Bathrooms	1975
Garages	1978
Kitchens	1987
Crawl spaces and unfinished basements	1990
Wet bar sinks	1993
Laundry and utility sinks	2005

AFCI requirements started later. They first appeared in the 1999 edition of the NEC, for bedroom circuits, with a required start date of January 1, 2002 [4]. The 2008 edition expanded them beyond bedrooms to areas like family rooms and dining rooms [3]. The 2014 edition added kitchens and laundry areas, and listed living rooms, dens, closets, hallways and similar spaces [5].

States and cities adopt the NEC on their own schedules and often amend it, so the rules in Raleigh, Charlotte, Atlanta or Dallas may not match the newest edition. For what applies to your home or project, check with your local building department or a licensed electrician.

Why older homes often don't have them

If your home was built before a requirement took effect, it was legal without that protection. Codes generally don't force you to upgrade existing wiring just because the rules changed. Protection usually gets added when work is done, such as a kitchen remodel, a new circuit or a panel replacement.

That's why a home report may list GFCI protection missing in wet areas. It doesn't mean the house was built wrong. It means a safety feature is missing in places where water and electricity meet.

Older homes often have two-slot outlets with no ground wire. A GFCI still works on these, and it can be used to replace one. The CPSC says an outlet protected this way must be labeled "No Equipment Ground" [1]. Grounding is a separate topic: see ungrounded receptacles.

How to test them

The CPSC and the Electrical Safety Foundation International (ESFI) both say to test GFCIs and AFCIs once a month [2, 3]. A GFCI can fail without any sign, so regular testing matters [2].

To test a GFCI outlet [1]:

Plug a lamp into the outlet and turn it on.
Press the "Test" button. The lamp should go off.
Press "Reset." The lamp should come back on.

If the lamp stays off after you press Reset, the GFCI needs to be replaced. If the lamp stays on when you press Test, the GFCI isn't working or was wired incorrectly. Either way, have a licensed electrician check it [1]. On a report, this shows up as a GFCI that isn't working properly.

To test a GFCI or AFCI breaker, press the test button on the breaker. It should trip. Then reset it following the manufacturer's instructions. If it doesn't trip when tested, ESFI says it should be replaced [3], and the CPSC says a defective AFCI breaker should be replaced by a qualified electrician [2].

Also test GFCIs after a power outage [1].

If a GFCI or AFCI keeps tripping

A device that trips is doing its job. Don't keep resetting it, and never replace it with a standard outlet or breaker to make the tripping stop. Unplug what's on the circuit and call a licensed electrician to find the cause.

Adding protection

Adding GFCI outlets or AFCI breakers involves working inside outlet boxes or the panel. ESFI says AFCIs should only be installed or replaced by a licensed, qualified electrician [3]. The same goes for GFCI breakers and outlets.

For what HomeCloud reports price this work at, see what GFCI outlets cost and outlet repairs. AFCI breakers go in the panel, so read what kind of electrical panel do I have? if your panel is old. HomeCloud is a licensed general contractor that evaluates homes and prices and does the repairs, and you can request an estimate.