To wire a light switch and an outlet together in a single 1-gang box where the switch controls a separate overhead light and the outlet remains always-hot, use a 15A combo switch/receptacle device (such as the Leviton 5225) wired with 14 AWG NM-B (Romex) cable on a 15A breaker. The incoming black hot wire lands on the brass LINE screw, the white neutral lands on the silver screw, the bare ground lands on the green screw, and the black switched-hot wire running to the light fixture lands on the black LOAD screw.

This guide walks through the exact terminal assignments, NEC sizing requirements, and testing procedures to get this done safely and correctly on the first try.

The Decision Path: Which Configuration Do You Need?

Before stripping any wire, you must define the functional relationship between the switch and the outlet. Combo devices and standard duplex receptacles handle power routing differently. Use this decision table to lock in your exact hardware pick.

If Your Goal Is... Then Your Configuration Is... Concrete Part Pick (Default)
Switch controls an overhead light; outlet is ALWAYS hot. Single-pole switch and 15A duplex receptacle combined in one 1-gang yoke. Leviton 5225-W (15A Combo Switch/Outlet)
Switch controls the outlet itself (turns a plugged-in lamp on/off). Single-pole switch and receptacle where the switch interrupts the hot feed to the receptacle. Leviton 5243-W (Switch controls outlet, no always-hot)
Half-switched outlet (top half switched, bottom half always hot). Standard duplex receptacle with the hot-side brass fin broken off, fed by 14/3 NM-B. Leviton 5262-W (Standard 15A Duplex, fin removed)
Bench Default: For 90% of residential retrofits and new additions where a single box must serve a wall plug and a ceiling fixture, the Leviton 5225-W on a 14 AWG / 15A circuit is the definitive pick. The rest of this guide assumes this exact configuration.

Tools, Materials, and NEC Sizing Requirements

Matching your wire gauge to your breaker and device rating is non-negotiable. NEC Article 210.21(B) dictates that a single receptacle on an individual branch circuit must have an ampere rating not less than that of the branch circuit. For a standard 15A lighting/receptacle circuit, here is your exact bill of materials.

Wire and Breaker Sizing

  • Breaker: 15A Single-Pole (e.g., Eaton BR115 or Square D QO115).
  • Wire Gauge: 14 AWG Copper minimum. (If your home uses 12 AWG on a 20A breaker, you must use a 20A combo device like the Leviton 5242 and 12 AWG pigtails).
  • Cable Type: 14/2 NM-B (Romex) for the line feed from the panel, and a second 14/2 NM-B for the switch leg running to the light fixture.

Tools and Hardware List

  • Combo Device: Leviton 5225-W (15A, 120V, Single-Pole Switch / Duplex Receptacle).
  • Wire Strippers: Klein Tools 11055 (calibrated for 14-10 AWG solid copper).
  • Wire Connectors: Ideal 33-Orange (Twister) wire nuts, rated for three 14 AWG wires.
  • Voltage Tester: Fluke 1AC-II Non-Contact Voltage Tester (NCVT) AND a solenoid tester or digital multimeter (e.g., Klein Tools MM400) for dead-front verification.
  • Receptacle Tester: Gardner Bender GRT-350 (for final ground/polarity verification).

Critical Safety Protocol: De-Energize and Verify

WARNING: Lethal Voltage Present. Working inside an electrical box exposes you to 120V AC, which can cause fatal ventricular fibrillation. Never rely solely on a wall switch to de-energize a circuit.
  1. Turn off the 15A breaker at the main service panel.
  2. Apply a lockout/tagout device to the breaker panel if you are not in direct sight of it.
  3. Test your NCVT on a known live source (like an extension cord) to verify the tester works.
  4. Insert the NCVT into the target outlet and sweep it across the switch. It must remain silent/unlit.
  5. Remove the faceplate, expose the wires, and verify dead with a multimeter: measure from the black hot wire to the bare ground wire. The reading must be 0.00V.

Note: NEC-style guidance is provided here; your local Authority Having Jurisdiction (AHJ) or inspector has final authority on permitting and code compliance. If you are unsure, hire a licensed electrician.

Step-by-Step Wiring Procedure

This procedure assumes you have a 1-gang fiberglass or metal box with two 14/2 NM-B cables entering it: one bringing power from the panel (Line), and one carrying power to the overhead light fixture (Load). Per NEC 404.2(C), a neutral conductor must be present at the switch location, which is why the white wire from the light fixture cable is capped in the box.

  1. Prep the Grounding System: Strip 3/4 inch of insulation from the bare copper ground wires on both 14/2 cables. Twist them together with a 6-inch 14 AWG bare copper pigtail. Secure with an orange wire nut. Connect the other end of the pigtail to the Green Ground Screw on the Leviton 5225. (If using a metal box, a second pigtail must bond the box to the ground wire bundle).
  2. Terminate the Neutrals: Strip 3/4 inch from the white neutral wires on both cables. Twist them together with a 6-inch 14 AWG white pigtail. Secure with a wire nut. Connect the pigtail to the Silver Neutral Screw on the combo device. Do not land two wires under a single screw terminal; always use a pigtail.
  3. Connect the Line Hot (Always-Hot Feed): Identify the black wire coming from the breaker panel. Strip 3/4 inch of insulation. Loop it clockwise around the Brass Screw marked 'LINE' (or the brass screw closest to the receptacle slots). Tighten to 12-14 in-lbs. This feeds constant power to the outlet half of the device.
  4. Connect the Switched Hot (To the Light): Identify the black wire from the cable running up to the ceiling light fixture. Strip 3/4 inch of insulation. Loop it clockwise around the Black Screw marked 'LOAD' (or the dark-colored screw isolated on the switch side). This is the switched leg. When you flip the rocker, this terminal receives 120V.
  5. Cap the Fixture Neutral: The white wire from the ceiling light cable is already tied into the neutral bundle in Step 2. This satisfies the NEC requirement for a neutral at the switch box, which is necessary for modern smart switches or LED drivers.
  6. Fold and Mount: Carefully fold the wires into the back of the box. Push the grounds and neutrals to the back, and fold the hots to the sides. Drive the 6-32 mounting screws into the box ears. Use a torpedo level to ensure the yoke is perfectly plumb before tightening fully.

The Most Common Botch: Reversing Line and Load

The single most frequent mistake DIYers make when wiring combo switch/outlet devices is swapping the Line (panel hot) and Load (light fixture hot) wires.

The Symptom: You turn on the breaker. The overhead light is on immediately and will not turn off. When you plug a lamp into the outlet and flip the switch, the plugged-in lamp turns on and off, but the ceiling light remains blazing.

The Physics: By landing the panel hot on the Black (Load) screw, you are feeding constant 120V directly to the ceiling fixture, bypassing the internal switch mechanism entirely. Simultaneously, the wire going to the ceiling is backfeeding 120V into the Brass (Line) screw, which energizes the outlet, but only when the internal switch is closed.

The Fix: De-energize the breaker, pull the device out, and swap the black wires. Panel hot always goes to Brass (Line). Fixture hot always goes to Black (Load).

Verify and Test: Expected Meter Readings

Do not button up the wall and assume success. Perform these three verifications before installing the faceplate.

1. Multimeter Voltage Test (Energized)

Turn the breaker back on. Set your multimeter to AC Voltage (V~).

  • Test 1 (Outlet Power): Probe the Brass Line screw and the Silver Neutral screw. Expected Reading: 114V to 126V.
  • Test 2 (Switch Off): Probe the Black Load screw and the Silver Neutral screw. Expected Reading: 0.0V.
  • Test 3 (Switch On): Flip the rocker switch to ON. Probe the Black Load screw and the Silver Neutral screw. Expected Reading: 114V to 126V.

2. Receptacle Polarity and Ground Test

Plug the Gardner Bender GRT-350 into the top and bottom receptacle slots.

  • Expected Indication: Two yellow lights (Correct Wiring).
  • If you see the red light: You have reversed hot and neutral (Black on Silver, White on Brass). Turn off the breaker and swap them immediately; this is a severe shock hazard.

3. Mechanical Verification

Plug a high-draw load (like a 1500W space heater or a heavy-duty work light) into the outlet to ensure the 15A contacts grip the plug blades tightly without arcing or excessive heat buildup after 5 minutes of operation. Verify the overhead light turns on and off crisply without flickering, which would indicate a loose wire nut on the switched-hot leg.