Bathroom Outlet Wiring: Code Requirements and Wire Selection
Bathroom outlet wiring is one of the most code-specific wiring tasks in residential construction because the NEC has explicit requirements that differ from standard outlet circuits elsewhere in the home. Using the wrong wire gauge, skipping GFCI protection, or sharing the circuit with other loads are among the most common bathroom wiring violations caught by inspectors. Here is a complete guide to getting it right.
The NEC Bathroom Outlet Requirements
The National Electrical Code (NEC) Section 210.11(C)(3) requires at least one dedicated 20-amp branch circuit for bathroom receptacle outlets. This circuit must supply only bathroom receptacle outlets and must not serve any loads outside the bathroom, including lights, exhaust fans, or outlets in adjacent rooms. A dedicated circuit means the circuit serves only the bathroom receptacles and nothing else. Section 210.8(A)(1) requires GFCI protection for all 125-volt, 15-amp, and 20-amp receptacles in bathrooms without exception.
Correct Wire: 12/2 NM-B on a 20-Amp Circuit
Because the circuit must be 20 amps, the minimum wire gauge is 12 AWG. Use 12/2 NM-B (Romex) for the run from the panel to the bathroom outlet location. A 12/2 cable contains the black hot conductor, white neutral conductor, and bare copper ground that the circuit requires. Pair the 12/2 NM-B with a 20-amp single-pole breaker in the panel and a GFCI outlet at the first receptacle location in the bathroom.
Do not use 14/2 NM-B for bathroom outlets. Installing 14 AWG wire on a 20-amp breaker is a code violation and a fire hazard. Inspectors specifically check bathroom circuits for correct wire gauge because this is a frequent error made by DIYers who do not understand the dedicated 20-amp requirement.
GFCI: Required at Every Bathroom Outlet
Every receptacle in a bathroom requires GFCI protection regardless of its distance from a water source. GFCI protection can be provided in one of two ways. A GFCI outlet at the first receptacle in the circuit with downstream protection for additional outlets on the same circuit wired through the LOAD terminals on the GFCI device. Or a GFCI circuit breaker in the panel that protects the entire circuit. Either method satisfies code. In bathrooms with a single outlet, a GFCI outlet is the simpler and less expensive approach. In bathrooms with multiple outlets or in new construction where panel space is available, a GFCI breaker protects all outlets with one device.
Can One Circuit Serve Multiple Bathrooms?
Yes, with one important condition. A single 20-amp bathroom circuit may supply receptacle outlets in more than one bathroom, but if it does, it must supply receptacle outlets only and nothing else in any of those bathrooms. The circuit cannot include the exhaust fan, lighting, or heated towel bars from any of the bathrooms it serves. Alternatively, each bathroom can have its own dedicated 20-amp circuit that also serves the lighting and exhaust fan in that specific bathroom, but not any loads outside the bathroom. This flexibility allows builders to choose between a shared bathroom receptacle circuit or individual bathroom circuits depending on panel capacity and project scope.
Exhaust Fan and Lighting Wiring
The bathroom exhaust fan and lighting do not need to share the receptacle circuit. They are typically wired on a separate 15-amp circuit using 14/2 NM-B, or included on an existing general-purpose lighting circuit if a dedicated bathroom circuit is not used for those loads. Many modern bathroom remodels install combination exhaust fan and light units that require only one circuit connection for both functions.
Wire Length and Voltage Drop
For most residential bathroom circuits where the panel is within 50 to 75 feet of the bathroom, voltage drop on a 12 AWG conductor is not a concern. For very long runs in large homes where the bathroom is 100 or more feet from the panel, upsizing to 10 AWG for the branch circuit run reduces voltage drop and maintains full outlet voltage at the receptacle.
IB Lighting carries 12/2 NM-B Romex from Southwire and Cerrowire in 250-foot and 1,000-foot spools with free freight insurance. Browse our electrical wire and cable selection or call (800) 674-9019 for contractor pricing on bulk orders.