Master electrician guide to wiring a garage outlet

Scope and code baseline

Attached garage, detached garage, shop space behind the house... the receptacle rules converge, but the supply path changes. Confirm whether the structure is served by a feeder or a single branch circuit before you plan anything else. That one decision drives your disconnect, grounding, and GFCI strategy.

Default to the 2023 NEC unless the AHJ has adopted an older cycle. Check the permit desk before pulling wire. Local amendments on GFCI locations and EV readiness are common and they override the base code.

Baseline articles you will reference on almost every garage job:

• NEC 210.8(A)(2) and 210.8(A)(11), GFCI for 125V through 250V receptacles in garages and accessory buildings
• NEC 210.52(G), required receptacle outlets in attached and detached garages with electric power
• NEC 210.11(C)(4), at least one 20A branch circuit dedicated to garage receptacles
• NEC 250.32, grounding and bonding for separate buildings or structures

Circuit sizing and receptacle count

210.52(G)(1) requires at least one receptacle in each vehicle bay, not less than one per car space, and within 5-1/2 feet of the floor. 210.11(C)(4) requires at least one 20A branch circuit serving only garage receptacles, though that circuit may also feed readily accessible outdoor receptacles on the same structure.

For a typical two-bay attached garage, pull 12/2 with ground on a 20A breaker, land a minimum of two receptacles inside the bays plus any required outdoor receptacles under 210.52(E). If the homeowner mentions a compressor, welder, or Level 2 EVSE, stop and resize. A 240V EVSE load falls under 625 and is never on the general-use garage circuit.

Quick load sanity check before you commit to #12:

1. Add nameplate amps of any known fixed tool that will live on the circuit
2. Confirm total continuous load stays at or below 16A on a 20A circuit (80% rule, 210.19)
3. If a door opener is on the same circuit, account for locked-rotor inrush, not just running amps
4. If the garage is detached, size the feeder to the structure, not just the branch

GFCI, AFCI, and the 2023 tweaks

Every 125V through 250V, 15A and 20A receptacle in a garage or accessory building requires GFCI protection per 210.8(A)(2) and (A)(11). That includes the 240V receptacle for a welder or compressor. Use a 2-pole GFCI breaker for 240V loads, since GFCI receptacles that cover straight 240V are rare and expensive.

AFCI is not required in garages by 210.12 in the 2023 NEC, but some states have amendments pulling it in. Verify locally. Where AFCI is required on an upstream circuit that extends into the garage, a dual-function breaker keeps your panel tidy.

If a customer has had nuisance trips on an old GFCI feeding a freezer, do not hand them a non-GFCI receptacle. 210.8(A) has no freezer exception anymore. Move the freezer to a dedicated circuit with a high-quality GFCI device and log the change on the permit.

Boxes, mounting, and physical protection

Use a 4 square box with a raised device cover for surface mounts on CMU or exposed stud walls. In finished drywall, a standard 20 cubic inch single-gang is fine for one 20A receptacle and a 12 AWG pair. Do the box fill math anyway per 314.16, especially if you are daisy-chaining.

Mounting height for the required 210.52(G) receptacle is capped at 5-1/2 feet above the floor. Nothing stops you from adding additional receptacles higher for a workbench or ceiling-mounted opener. NM cable run exposed below 7 feet needs physical protection per 334.15(B), so either furr it out, run EMT, or switch to MC.

Common box and cable calls on a garage rough-in:

• Exposed masonry: 4 square with mud ring, EMT or MC whips
• Finished garage: single-gang plastic or metal, NM-B inside stud bays
• Ceiling receptacle for opener: 4 square with fixture ring, strain relief rated for the cable type
• Below 7 feet exposed: EMT, RMC, or running boards per 334.15

Detached garages and the feeder question

Once the structure is detached, 225 and 250.32 take over. You need a disconnect at or inside the detached structure per 225.31 and 225.32, and you need to establish a grounding electrode system at that building per 250.32(A). The equipment grounding conductor runs with the feeder, and you do not re-bond neutral to ground at the subpanel.

For a typical detached single-family garage, a 60A feeder in 6/3 with ground from the main panel to a small loadcenter covers lighting, receptacles, an opener, and leaves room for a future EVSE. Direct burial UF works, but most inspectors prefer PVC with THWN-2 for long pulls and future pull-ability.

If the existing detached garage has an old 3-wire feeder with a bonded neutral, fix it on this visit. 250.32(B) no longer permits the re-identified neutral as the EGC for new or modified installations, and the inspector will flag it the moment they see a new permit on that structure.

Testing and closeout

Trip-test every GFCI with a plug-in tester and the device button, not just one or the other. Verify open ground and reversed polarity while you are there. Log the readings, photograph the panel directory, and leave a clean schedule behind the deadfront.

Before you call for inspection, walk the garage with the homeowner and confirm what will live on each receptacle. If a welder or EV charger shows up in that conversation, revise the permit now rather than after rough-in sign-off.