Both are life-safety devices, and they protect against different things. GFCIs protect people from shock; AFCIs protect homes from fires started by arcing wires.
What does a GFCI do?
A ground-fault circuit interrupter compares the current going out on the hot wire with the current coming back on the neutral. If a few thousandths of an amp go missing (for example through a person to ground), it shuts off in a fraction of a second. GFCIs come as outlets (with TEST and RESET buttons) or as breakers.
What does an AFCI do?
An arc-fault circuit interrupter watches for the electrical signature of arcing, the kind caused by damaged cords, loose connections or a nail through a cable, and shuts off the circuit before it can start a fire. AFCIs are usually breakers, sometimes outlets at the start of a circuit.
Dual-function (AFCI/GFCI) breakers do both and are common where both are required, such as kitchens and laundry areas.
Where are GFCI and AFCI required?
Requirements have grown with each code edition. In general terms under the code now adopted in California:
- GFCI: bathrooms, kitchens, garages and accessory buildings, outdoors, crawlspaces and unfinished basements, laundry areas, near sinks, and around pools, spas and hot tubs, including many 240-volt outlets in those areas.
- AFCI: most 120-volt, 15- and 20-amp circuits feeding living areas such as bedrooms, living and family rooms, dining rooms, kitchens, hallways, closets and laundry areas.
Older homes are generally not required to be updated until the circuits are changed or extended, but adding the protection is a strong safety upgrade.
Why does my GFCI keep tripping?
Water in an outdoor box, a failing appliance (old freezers, refrigerators and power tools are common), damaged cords, or too many devices downstream. Unplug everything on that circuit, reset, then plug things back one at a time to find the culprit.
How to test a GFCI outlet
- Plug in a lamp. Plug a lamp or a plug-in tester into the GFCI outlet and turn it on.
- Press TEST. Press the TEST button. The lamp should go off.
- Press RESET. Press RESET firmly. The lamp should come back on.
- If it fails. If the lamp does not go off, or the GFCI will not reset, stop using the outlet and have it replaced.
Common questions
What is the difference between a GFCI and an AFCI?
A GFCI protects people from electric shock by detecting current leaking to ground. An AFCI helps prevent fires by detecting dangerous arcing in wiring and cords. Dual-function devices do both.
How often should I test a GFCI?
Monthly is the common recommendation. Press TEST, confirm power goes off, then press RESET.
Why does my AFCI breaker trip for no reason?
Real arcing from a damaged cord or loose connection, some older motor-driven appliances, or a wiring fault such as a shared neutral. Repeated trips should be checked by an electrician.
General information for California homes under the California Electrical Code (based on the NEC). Local rules and inspectors can vary. Not a substitute for an on-site inspection. Never work inside a panel, at the meter or on live circuits.