Bathroom Electrical Remodel: Complete Wiring Guide
Bill of materials
Bathrooms were the first location to require GFCI protection (since 1975) and remain among the most heavily regulated spaces in the NEC. Every bathroom needs a dedicated 20A circuit that does not share loads with any other room. All bathroom receptacles require GFCI, and NEC 2023 requires AFCI for all 15A/20A dwelling circuits.
NEC 210.11(C)(3) requires a dedicated 20A circuit for bathroom receptacles. This circuit may also supply other equipment in the same bathroom (lighting, exhaust fan) per 210.11(C)(3) exception, but cannot extend to other rooms. All receptacles require GFCI per 210.8(A)(1). A dual-function AFCI/GFCI breaker satisfies both requirements. Exhaust fans in shower areas must be rated for wet/damp locations.
Bathroom receptacle circuit (20A)
| Component | Specification | NEC basis |
|---|---|---|
| Wire (copper) | 12 AWG THHN | Table 310.16, 110.14(C) |
| Breaker | 20A double-pole | 240.4 |
| Voltage | 120V single-phase | |
| Conduit (EMT) | 1/2" EMT | Chapter 9 Table 4 |
| GFCI | Required (GFCI breaker or device) | 210.8(A)(1) |
| Max distance (3% VD) | 56 ft at 120V copper | 210.19(A) Note 4 |
Installation notes
This project requires GFCI protection per NEC 210.8(A)(1). The simplest approach is a GFCI breaker at the panel, which protects the entire circuit. For 240V circuits, use a 2-pole GFCI breaker sized to match the circuit. GFCI breakers cost $40-80 depending on amperage.
Standard 120V circuits use NM-B cable with 12/2 cable (hot, neutral, ground). For conduit runs, pull individual 12 AWG THHN conductors. All connections must be made in accessible junction boxes.
Run length matters: every foot of wire adds voltage drop, reducing power to your equipment. The table below shows the exact voltage drop at common distances. If your run exceeds the 3% threshold, upsize one gauge.
Voltage drop by distance
Percentage voltage drop at common run lengths. NEC recommends 3% maximum for branch circuits and 5% for combined feeder plus branch.
| Distance | 12 AWG Co | 10 AWG Co |
|---|---|---|
| 25 ft | 1.3% | 0.8% |
| 50 ft | 2.6% | 1.6% |
| 75 ft | 4.0% | 2.5% |
| 100 ft | 5.3% | 3.3% |
| 150 ft | 7.9% | 5.0% |
| 200 ft | 10.6% | 6.6% |
Common products for 12 AWG Copper circuits
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Related wire data
Detailed ampacity: 12 AWG copper. Wire size lookup: 20A circuit. Calculators: voltage drop · panel load calculator.
Inspection preparation
Before your rough-in inspection, verify these frequently-checked items:
| Check | NEC Ref | Common Fail |
|---|---|---|
| Cable secured within 12 inches of box | NEC 334.30(A) | NM cable not stapled close enough to box |
| Proper wire gauge for circuit amperage | NEC 240.4(D) | 14 AWG on 20A circuit or 12 AWG on 30A circuit |
| Ground wire continuous and properly bonded | NEC 250.148 | EGC not connected in box or spliced incorrectly |
| No NM cable in wet/damp locations | NEC 334.12(B) | Romex used in exterior, underground, or damp location |
| Box fill calculations | NEC 314.16 | Too many conductors in box |
See the full inspection checklist tool for all 19 items with progress tracking.
Frequently asked questions
What wire size do I need for bathroom electrical remodel?
Use 12 AWG copper or 12 AWG aluminum on a 20A breaker at 120V. This is based on NEC 2023 Table 310.16 ampacity with 110.14(C) termination limits and 125% continuous load sizing per 210.19(A)(1).
Does bathroom electrical remodel require GFCI?
Yes. GFCI protection is required per NEC 210.8(A)(1).
NEC 2023 references verified April 2026