AFCI vs GFCI: What Each One Protects You From

AFCI (arc-fault circuit interrupter) detects the electrical signature of arcing — the sparking in damaged or loose wiring that starts fires — and protects the building. GFCI (ground-fault circuit interrupter) detects current escaping to ground and cuts power in a fraction of a second to protect a person from electrocution.

Neither substitutes for the other. They watch for different things, trip on different conditions, and the NEC requires them in different places — with some locations now requiring both, which is what a dual-function (DF) breaker provides.

AFCI vs GFCI at a glance

Two devices, both with a small TEST button, both required by the NEC in modern homes, protecting against entirely different things. Confusing them is common and consequential, because installing the wrong one leaves the actual hazard unaddressed.

GFCI: protects people

A ground-fault circuit interrupter watches the current going out on the energized conductor and the current coming back on the neutral. In a healthy circuit those are equal. If they differ, current is returning by some other route — through a water pipe, through damp concrete, through a person.

GFCIs trip at roughly 5 milliamps of imbalance, in a fraction of a second. That threshold is set well below the level at which current across the chest can stop a heart, which is why the protection exists at all. It has nothing to do with the circuit's overcurrent rating.

Where the NEC requires it (dwelling units, in general terms — the exact list expands with each code cycle and your jurisdiction's adopted edition governs):

• Bathrooms
• Kitchens — receptacles serving countertop surfaces
• Garages and accessory buildings
• Outdoors
• Crawl spaces and unfinished basements
• Laundry areas
• Receptacles within 6 feet of a sink, tub, or shower
• Boathouses and areas near pools and spas

Recent code cycles have extended GFCI requirements to certain 240-volt appliance circuits and to outdoor outlets for equipment. If you're doing work now, ask what your jurisdiction has adopted.

Where you find it: a GFCI receptacle (with TEST and RESET buttons) protects itself and everything downstream of it on that circuit. A GFCI breaker protects the entire circuit from the panel.

AFCI: protects the building

An arc-fault circuit interrupter looks for the electrical signature of arcing — the erratic, high-frequency pattern current makes when jumping a gap.

Arcing matters because a series arc — a loose terminal, a cracked conductor, a cable pinched by a staple — produces intense localized heat while drawing less current than normal. A standard breaker never sees anything wrong. The arc quietly chars the surrounding material for months.

Electrical arcing is a recognized ignition source in residential structure fires, and AFCI requirements exist specifically to catch a failure mode that overcurrent protection is blind to.

Where the NEC requires it: broadly, most 120-volt, 15- and 20-amp branch circuits supplying outlets in dwelling-unit living areas — bedrooms, living rooms, dining rooms, hallways, closets, kitchens, laundry areas, and similar spaces. The scope has widened over successive code cycles; earlier editions covered bedrooms only, which is why an older home may have AFCI on only part of the panel.

Where you find it: usually as a breaker in the panel, since it needs to monitor the whole circuit including the wiring in the walls. AFCI receptacles exist but protect only downstream of their location.

Side by side

Do I need both AFCI and GFCI?

Many circuits fall under both requirements — a kitchen or laundry circuit needs arc-fault protection as a living-area circuit and ground-fault protection because of water. Dual-function breakers and receptacles provide both.

They're more expensive per device, which is a real factor in a panel replacement where 20 or 30 circuits are being reconnected to current requirements. It's also a common source of variation between quotes — see electrical panel upgrade cost.

Testing them

Both device types have a TEST button, and both should be tested periodically — monthly is the common manufacturer recommendation.

• Press TEST. The device should trip and power should cut.
• Press RESET. Power should return.

A device that doesn't trip on TEST has failed and must be replaced. A device that trips but won't reset is either faulty or reporting a real, present fault on the circuit.

This test costs nothing and is the only way to know these devices still work. A GFCI that has failed provides no warning of its failure.

Common problems

GFCI trips repeatedly. Usually moisture or a failing appliance. Outdoor receptacles after rain, old refrigerators, and well pumps are frequent causes. See why does my GFCI keep tripping.

AFCI nuisance trips. Motor brushes and switching power supplies can produce arc-like signatures. Newer designs are better at discriminating. Don't solve it by swapping in a standard breaker — that's removing fire protection to silence an alarm. See AFCI breakers explained.

One tripped device kills several rooms. Normal. A GFCI receptacle protects everything downstream, so the reset button may be in a different room, often a bathroom or the garage.

Code reference

The requirements behind this guide, for looking up in your adopted edition:

• NEC 210.8 — GFCI protection and required locations
• NEC 210.12 — arc-fault circuit-interrupter protection and required locations

Code editions and local amendments vary by jurisdiction. Confirm the adopted edition with your AHJ before relying on any specific article.

Where to go next

• AFCI breakers explained
• Why does my GFCI keep tripping
• Types of circuit breakers
• Wire & breaker size chart

More in our electrical panel guides.