GFCI vs. AFCI Protection: What They Do, Where Code Requires Them, and How to Test Them
Published 8/13/2026
The short answer: GFCIs and AFCIs are two different safety devices that protect against two different dangers. A GFCI (ground-fault circuit interrupter) protects people from electric shock by cutting power the instant it detects electricity leaking to ground.[1] An AFCI (arc-fault circuit interrupter) protects your home from fire by shutting off a circuit when it senses the dangerous arcing that damaged or aging wiring can produce.[3] Modern electrical codes require both, in different parts of the house — and you should test them about once a month.
What a GFCI does
A GFCI constantly compares the current flowing out to a device with the current returning from it. When those amounts differ by even a tiny margin — as little as about 5 to 6 milliamperes — it means electricity is escaping along an unintended path, possibly through a person, and the GFCI cuts power almost instantly.[1] OSHA describes the mechanism the same way: the device works "by comparing the amount of current going to and returning from equipment," and when the difference reaches roughly 5 milliamperes it "interrupts the current" within as little as 1/40 of a second.[8] The CPSC notes it is "designed to operate before the electricity can affect your heartbeat."[1]
One useful limitation to understand: a GFCI protects against ground faults — the most common shock hazard — but it "will not protect you from line contact hazards," such as touching a hot and a neutral wire at the same time.[8] (You may see these devices labeled "GFI"; it is the same thing, and they come as receptacles, circuit breakers, and portable plug-in units.[5])
What an AFCI does
An arc fault is "a dangerous electrical problem caused by damaged, overheated, or stressed electrical wiring or devices," and the arcs it creates can reach very high temperatures and ignite surrounding material.[3] An AFCI recognizes the distinctive electrical signature of that arcing — whether a series arc along a single damaged conductor or a parallel arc between wires — and de-energizes the circuit before a fire can start.[3] The CPSC estimates that "more than 50% of electrical fires that occur every year can be prevented by Arc-Fault Circuit Interrupters."[4]
The scale of the underlying hazard is significant. The Electrical Safety Foundation International reports that electrical fires cause roughly 51,000 fires each year, nearly 500 deaths, more than 1,400 injuries, and about $1.3 billion in property damage, with arcing faults alone behind more than 28,000 home fires annually.[2]
GFCI vs. AFCI at a glance
GFCI
AFCI
Primarily protects
People, from electric shock
Property, from electrical fire
What it detects
Current leaking to ground (~5–6 mA imbalance)[1]
Dangerous arcing in wiring/cords[3]
Typical locations
Kitchens, baths, garages, basements, outdoors[5]
Most living-area circuits (bedrooms, living/family rooms, etc.)[4]
Comes as
Receptacle, breaker, or portable unit[5]
Breaker or receptacle[3]
You can also get a single dual-function AFCI/GFCI device that "provides protection against arc-faults as well as ground faults."[6] Note the terminology trap: a "combination" AFCI breaker refers to one that catches both series and parallel arcs, while "dual-function" is the term that means it does both AFCI and GFCI jobs.[6]
Where code requires them
The National Electrical Code (NEC) has steadily expanded both requirements over the decades. As a general picture of current practice:
GFCI protection is required in wet or damp areas. The CPSC's history of NEC additions runs from outdoors (1973) and bathrooms (1975) through garages, kitchens, crawl spaces and unfinished basements, and laundry areas.[1] ESFI summarizes today's coverage as "all kitchens, bathrooms, garages, basements, crawlspaces, and outdoors."[5]
AFCI protection covers most living-area branch circuits — ESFI lists bedrooms, closets, kitchens, laundry areas, living rooms, family and rec rooms, dining rooms, and similar spaces.[4]
How to test them — do this monthly
Both devices can wear out while an outlet still delivers power, so testing is not optional. The CPSC recommends testing every GFCI after installation, at least once a month, and after any power failure.[1] The routine is simple:
Press the TEST button — power to the outlet (or circuit) should shut off. A quick check is to plug in a nightlight; if it does not turn off when you press TEST, "the GFCI is not working properly."[5]
Press RESET to restore power.
If it fails to trip or reset, replace it.[1]
Test AFCI breakers and receptacles the same way, once a month, using their TEST button.[3]
Why testing matters: devices can quietly fail
This is the part homeowners most often miss. A GFCI can stop protecting you and still power your devices normally, so nothing looks wrong until it is tested. Field studies found a number of installed units that had become inoperative, in part because "consumers seldom (if ever) push the 'Test' button."[7] In response, UL now requires GFCIs manufactured since June 29, 2015 to include an automatic self-test function that periodically checks the device and denies power when it reaches the end of its life.[7] Even so, self-testing does not check every internal component, so the monthly manual test is still worth doing — and any device that fails should be replaced.[7]
What they cost
These are affordable upgrades, especially measured against the hazards they address:
GFCI receptacle: roughly $15–$40 for the device; professional installation commonly runs about $130–$300, averaging around $210.[9]
AFCI breaker: roughly $35–$65 for a standard breaker (more for a combination AFCI/GFCI breaker), with installation often about $110–$215 per circuit; retrofitting a whole home of 10–20 circuits can reach $1,000–$4,000.[10]
Because this is work inside your electrical panel and involves life-safety devices, breaker installation in particular is a job for a licensed electrician.[3]
Frequently asked questions
Do I need both GFCIs and AFCIs?
Yes — they guard against different dangers. GFCIs protect people from shock in wet areas; AFCIs protect against fires from arcing in living-area circuits. Modern codes require both, and dual-function devices can provide both protections at once.[1][3][6]
My GFCI outlet still works — why test it?
Because a GFCI can lose its protective function while still delivering power. The only way to know it still protects you is to press TEST monthly; replace it if it fails.[1][7]
Is a GFCI the same as a GFI?
Yes. "GFI" and "GFCI" refer to the same ground-fault circuit interrupter; the devices come as receptacles, breakers, and portable plug-in units.[5]
Will a GFCI protect me from every kind of shock?
No. It protects against ground faults, the most common shock hazard, but not from contact across two current-carrying wires at once. It is powerful protection, not a guarantee to be careless around electricity.[8]