Bathroom Exhaust Fan: Wiring Requirements
Wiring a bathroom exhaust fan correctly means running 12 AWG copper on a dedicated 20-amp circuit with GFCI protection. This guide covers the complete wiring requirements per NEC 2023, including wire gauge, breaker size, cable type, and installation specifics for a bathroom or near water sources. Whether you are hiring an electrician or planning the circuit yourself, the specifications below ensure your installation meets code.
What usually triggers this search
You're replacing a bathroom appliance or adding one that needs its own circuit. Bathrooms have strict dedicated circuit and GFCI requirements that date back decades.
What goes wrong
Bathroom circuits have the longest history of GFCI requirements in the code (since 1975), but problems persist. The most common failure: the bathroom 20A circuit also serves the hallway outlet on the other side of the shared wall. Per 210.11(C)(3), the required bathroom circuit can serve one or more bathrooms but cannot serve other rooms. Moisture intrusion into boxes and receptacles accelerates corrosion on terminals. Loose connections in a humid environment arc, and arc-damaged receptacles are a fire hazard that looks normal from the outside.
What the inspector checks
- Dedicated 20A circuit serving only bathroom(s) per 210.11(C)(3)
- GFCI protection on all bathroom receptacles per 210.8(A)(1)
- 12 AWG minimum on the 20A bathroom circuit
- At least one receptacle outlet on each side of the basin
Should you hire an electrician?
Replacing a bathroom receptacle or fixture is straightforward DIY work if the circuit is already properly wired. Adding a new circuit for a bathroom requires an electrician in most cases. Budget $200-400 for a new bathroom circuit.
Bathroom Exhaust Fan electrical specifications
| Minimum wire gauge | 12 AWG copper |
| Breaker size | 20A single-pole |
| Voltage | 120V (120V single-phase) |
| Typical draw | 10-100W (0.1-0.8A) |
| Dedicated circuit | Yes - no other loads on this breaker |
| Cable type | 12/2 NM-B (Romex) or 12 AWG THHN in conduit |
| GFCI required | Yes - NEC 210.8(A) |
Circuit requirements for bathroom exhaust fan
A bathroom exhaust fan must have a dedicated circuit - no other appliances, outlets, or loads should share this breaker. This means running a new 12/2 NM-B cable from the electrical panel directly to the appliance location.
Wire sizing: The minimum wire for a 20A circuit is 12 AWG copper. Use 12/2 NM-B cable (hot, neutral, ground) for standard residential runs in walls and attics. For wire runs over 50 feet, check voltage drop - you may need to upsize to 10 AWG to keep voltage drop under 3%.
Breaker sizing: A 20A breaker (single-pole, 120V) protects this circuit. The breaker must match or exceed the appliance nameplate rating but never exceed the wire capacity. 12 AWG copper is rated for well above 20A, providing adequate safety margin.
Installation notes
Bathroom circuit rules: NEC 210.11(C)(3) requires a dedicated 20A circuit for bathroom receptacles. All bathroom receptacles require GFCI protection. A bathroom exhaust fan on a separate switch can share the lighting circuit, but receptacle outlets must be on the dedicated 20A circuit.
Receptacle type: Use standard NEMA 5-20R (T-slot) receptacles on 20A circuits, or NEMA 5-15R on 15A circuits. All receptacles must be tamper-resistant (TR) in new construction per NEC 406.12.
Safety and code requirements
GFCI protection is required for this appliance location. Install GFCI protection at the breaker (GFCI breaker) or at the first receptacle in the circuit. See Bathroom GFCI requirements for the full NEC rules and edition-by-edition changes.
Ground wire: The equipment grounding conductor (green or bare wire) must be continuous from the panel to the appliance. For a 20A circuit, the minimum ground wire is 12 AWG copper per NEC Table 250.122. NM-B cable includes the correct ground wire size automatically.
Permits: Most jurisdictions require an electrical permit for adding a new circuit. The inspector will verify wire size, breaker rating, grounding, and GFCI protection. Check your state’s NEC adoption and call your local building department before starting work.
Typical installation
The cable run typically goes from the panel through wall cavities to the bathroom. In a slab-on-grade home, the cable routes through the attic. In a two-story home, it may come up through the floor. The receptacle must be within 3 feet of the outside edge of the sink basin per NEC 210.52(D). GFCI protection is installed at the breaker or at the first receptacle in the circuit.
Estimated materials cost
For a typical 50-75 foot run, expect to spend approximately $51-$116 on materials:
| 12/2 NM-B cable (50-75 ft) | $18-$56 |
| 20A GFCI breaker | $33-$60 |
| Estimated materials total | $51-$116 |
Material costs are approximate based on retail pricing as of Feb 2026. Actual costs depend on cable length, local pricing, and copper market conditions. Does not include labor, permits, or inspection fees.
Frequently asked questions
What size wire do I need for a bathroom exhaust fan?
12 AWG copper on a 20A breaker at 120V. This is the minimum per NEC Table 310.16. For runs over 50 feet, check voltage drop and consider upsizing to 10 AWG.
Does a bathroom exhaust fan need a dedicated circuit?
Yes. A bathroom exhaust fan requires its own dedicated circuit - no other outlets or appliances can share the breaker.
Does a bathroom exhaust fan need GFCI protection?
Yes. Bathroom locations require GFCI protection under NEC 210.8(A). Install a GFCI breaker or GFCI-protected receptacle.
Can I wire a bathroom exhaust fan myself?
In most states, homeowners can do their own electrical work on their primary residence with a permit and inspection. However, this is not a DIY task if you are unfamiliar with electrical work - improper wiring can cause fires or electrocution. Check your state licensing requirements and always get a permit.
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NEC 2023 references verified April 2026