What is GFCI?

What this means for your home project

1. Locate the manufacturer’s test instructions and add a monthly reminder, including another test after a power failure. Source: U.S. Consumer Product Safety Commission (CPSC), read 2026-11-06.
2. Start the lamp test with the lamp illuminated so the TEST button’s effect is visible. Source: U.S. Consumer Product Safety Commission (CPSC), read 2026-11-06.
3. If the lamp stays on during TEST, request a written scope from an electrician identifying wiring correction or GFCI replacement. Source: U.S. Consumer Product Safety Commission (CPSC), read 2026-11-06.
4. For installed protection, ask the written proposal to identify a breaker-type or receptacle-type GFCI. Source: U.S. Consumer Product Safety Commission (CPSC), read 2026-11-06.

What is a ground fault?

A ground fault is an unintended electrical route to a grounded surface. CPSC (read 2026-11-06) describes it as an "unintentional electrical path" and identifies damaged or defective equipment as a frequent cause. Contact with exposed live parts can make a person part of that path. (source)

“A ground fault is an unintentional electrical path between a power source and a grounded surface.” (source) “Ground faults most often occur when equipment is damaged or defective, such that live electrical parts are no longer adequately protected from unintended contact.” (source) “If your body provides a path to the ground for this current, you could be burned, severely shocked or electrocuted.” (source)

How does a GFCI work?

A GFCI compares outgoing and returning current, interrupting power when a small difference indicates a ground fault. CPSC (read 2026-11-06) describes a difference "as little as 0.006 amperes"—six thousandths of an ampere. The protection responds to that imbalance rather than waiting for the person to disconnect the appliance. (source)

“A GFCI constantly monitors current flowing through a circuit.” (source) “If the current flowing into the circuit differs by a very small amount (as little as 0.006 amperes) from the returning current, the GFCI interrupts power faster than a blink of an eye to prevent a lethal dose of electricity.” (source)

What are the different types of GFCIs?

GFCI protection comes in installed and portable forms. CPSC (read 2026-11-06) describes a breaker mounted "in a panel box" to protect its supplied circuits, while a portable GFCI plugs into a receptacle. A receptacle GFCI is the wall-outlet form; the installation location distinguishes these options. (source)

“A circuit breaker with a built-in GFCI may be installed in a panel box to add protection to the circuits it supplies.” (source) “A portable GFCI gets plugged into a receptacle just like any other cord-and-plug-connected device.” (source) “Ground fault protection is integrated into GFCI receptacles and GFCI circuit breakers for installation into your electrical system, especially for circuit outlets in particularly vulnerable areas such as where electrical equipment is near water.” (source)

How often should I test my GFCI receptacles?

GFCI testing belongs on a recurring schedule. CPSC (read 2026-11-06) says "At least once a month" and also calls for testing after installation and a power failure, following the manufacturer’s instructions. A power interruption matters because disturbances can damage the device’s ability to work properly. (source)

“Test every GFCI: After installation At least once a month After a power failure According to the manufacturer's instructions.” (source) “Blackouts and other power disturbances can sometimes damage a GFCls ability to function properly.” (source)

How do I test a GFCI?

A GFCI test uses an observable loss and return of power. CPSC (read 2026-11-06)’s fallback procedure starts with "Plug a lamp into the outlet" and uses the TEST and RESET buttons. A lamp that stays on during TEST calls for an electrician to correct wiring or replace the device. (source)

“Plug a lamp into the outlet and turn the lamp on.” (source) “Press the GFCl's test button.” (source) “Did the light go out?” (source) “If not, the GFCI is not working or has not been correctly installed.” (source) “Contact a qualified electrician to correct the wiring and/or replace the defective GFCI.” (source) “Press the reset button.” (source) “Did the light come back on?” (source) “If not, replace the GFCI.” (source)

Do I need GFCI on every outlet?

GFCI protection can extend beyond the device’s own outlet. CPSC (read 2026-11-06) describes protection for outlets further "down stream" in the branch circuit and identifies the NEC as the source of circuit requirements. The NEC is NFPA 70; local adoption determines its legal application rather than a universal retrofit rule. (source)

“Fits into a standard outlet box and protects against ground-faults for whatever is plugged into the outlet and other electrical outlets further "down stream" in the branch circuit.” (source) “The circuits that require GFCI protection are designated by the National Electrical Code (NEC).” (source) “The NEC is published by the National Fire Portection Association (NFPA 70).” (source) “It may be adopted into law by states, counties or local jurisdictions for enforcement by inspection authorities and is currently revised every three years.” (source)

How do I install a GFCI?

GFCI installation work depends on its form: a portable unit plugs in, while installed breaker and receptacle forms involve electrical wiring. CPSC (read 2026-11-06) says to "contact a qualified electrician" when the procedure is uncertain. Describe which form you need when requesting the installation scope. (source)

“Circuit breaker and receptacle-type GFCls may be installed in your home by a qualified electrician.” (source) “Receptacle-type GFCls may be installed by consumers with adequate knowledge and skills to conform to proper electrical wiring practices and the instructions accompanying the device.” (source) “When in doubt about the proper procedure, contact a qualified electrician; do not attempt to install it yourself.” (source)

Sources

• What Is a GFCI? — CPSC Fact Sheet, Pub. 099 — U.S. Consumer Product Safety Commission (CPSC); published 2010-09; read 2026-11-06.