A light switch with outlet (often called a combo device or switch-receptacle) is the ultimate space-saver for single-gang boxes in garages, workshops, and basements. It replaces a standard toggle switch and a separate duplex receptacle with a single, unified yoke. However, because the internal bus architecture of these devices differs from standard standalone switches and outlets, they are a frequent source of wiring errors.

The direct answer for most standard residential applications (a 15-amp circuit controlling a separate ceiling light while providing an always-hot receptacle) is the Leviton 5241 (15A) or Leviton 5245 (20A). Below is the exact decision path, material list, and terminal-by-terminal wiring procedure to get it right on the first attempt.

Decision Tree: Which Combo Device Do You Actually Need?

Not all combo devices are wired the same internally. Before you strip a single wire, use this decision table to select the exact part number for your circuit's intended behavior.

Scenario / Goal Switch Behavior Outlet Behavior Concrete Device Pick
Standard workshop/garage drop Controls a separate hardwired light fixture. Always hot (unswitched) for plugging in tools. Leviton 5241 (15A) or 5245 (20A)
Switched holiday lighting outlet Controls a separate light fixture. Switched (turns on/off with the toggle). Leviton 5224 (Switched Receptacle Combo)
Kitchen/Bathroom 20A small appliance Controls a separate vanity or under-cabinet light. Always hot, must accept 20A T-slot plugs. Leviton 5245 (20A Duplex Combo)
3-Way switching requirement Must pair with another 3-way switch for the light. Always hot. Stop. Combo 3-way devices are rare and complex. Use a standard 3-way switch and relocate the outlet.

Default Recommendation: For 90% of DIY retrofits where you want to add an outlet to an existing single-gang switch box, you want an always-hot receptacle and a switch for the room light. Buy the Leviton 5241 (if on a 15A breaker) or Leviton 5245 (if on a 20A breaker).

Tools, Materials, and Device Ratings

Do not mix wire gauges and breaker ratings arbitrarily. The device rating must align with the circuit's overcurrent protection and the physical wire gauge in the wall.

Materials & Hardware

  • Combo Device: Leviton 5241 (15A, 125V) or Leviton 5245 (20A, 125V).
  • Wire: 14/2 NM-B (Romex) for 15A circuits, or 12/2 NM-B for 20A circuits. You will also need a 6-inch jumper wire of the exact same gauge and insulation type (THHN or solid NM-B core).
  • Wire Connectors: Ideal Yellow Wing-Nuts or 3M Performance Plus wire nuts (sized for your specific wire count).
  • Single-Gang Box: Must have a minimum volume of 14 cubic inches (for 14 AWG) or 16 cubic inches (for 12 AWG) to accommodate the combo device body and wire splices per NEC 314.16.

Tools

  • Voltage Tester: Non-contact voltage tester (e.g., Klein NCVT-2) AND a digital multimeter (e.g., Fluke 117 or Klein MM400) for two-point verification.
  • Wire Strippers: Klein 11055 (for 14 AWG) or Klein 11063 (for 12 AWG). Do not use the cutting holes to strip; you will nick the copper and create a hot spot.
  • Screwdriver: #2 Phillips and a 1/8-inch flathead. A torque screwdriver set to 14 in-lbs is recommended for terminal screws to prevent cold-flow loosening.

Mains Safety: De-Energize and Verify

CRITICAL SAFETY PROTOCOL: Working on a light switch with outlet involves 120V AC mains voltage, which is lethal. Never rely on a wall switch being 'off' to isolate power.
  1. Go to the main service panel and turn OFF the specific branch circuit breaker. If the panel is not clearly labeled, turn off the main breaker.
  2. Apply a lockout/tagout (LOTO) device to the breaker if others are in the home, or tape it in the OFF position.
  3. Test your non-contact voltage tester on a known live circuit (like an extension cord plugged into a different room) to verify the tester's battery and sensor are functioning.
  4. Remove the existing switch faceplate and test the wires in the box with the non-contact tester.
  5. Verify dead with a digital multimeter set to AC Voltage. Place one probe on the bare ground wire and the other on the black hot wire. The reading must be 0.0V. If it reads >2V, stop. You have the wrong breaker or a multi-wire branch circuit (MWBC) with a shared neutral that requires turning off two adjacent breakers.

NEC-style guidance: Your local Authority Having Jurisdiction (AHJ) has final authority. If you are unsure about panel work or MWBC identification, hire a licensed electrician.

Step-by-Step Wiring: Colors to Terminals

The following procedure assumes you are installing a Leviton 5241 (15A) to control a separate ceiling light while keeping the outlet always hot. This is the most common configuration.

Pro-Tip on Terminal Connections: Always wrap the wire clockwise around the screw terminal so that tightening the screw pulls the loop closed. Strip exactly 3/4-inch of insulation. No bare copper should be visible outside the terminal saddle, and no insulation should be pinched under the screw head.
  1. Prep the Ground (Bare/Green): Create a pigtail using a 6-inch piece of bare copper wire. Connect the incoming bare ground, the outgoing bare ground (to the light fixture), and the pigtail using a wire nut. Wrap the other end of the pigtail clockwise around the Green Ground Screw on the bottom of the combo device and tighten.
  2. Connect the Neutral (White): The switch portion of the combo device does not use a neutral, but the receptacle does. Splice the incoming white neutral and the outgoing white neutral (to the light fixture) together with a wire nut. Add a 6-inch white pigtail to this bundle. Connect the other end of the white pigtail to the Silver Terminal Screw on the receptacle side of the device.
  3. Connect the Line Hot (Black): Identify the incoming black hot wire from the breaker panel. Connect this black wire directly to the Black Line Screw on the switch portion of the combo device. (This screw is usually marked 'LINE' or is distinctly colored black compared to the brass screws).
  4. Install the Always-Hot Jumper (Crucial Step): The Leviton 5241 does not internally feed the receptacle from the line screw. Take a 6-inch black jumper wire (same gauge as your circuit). Attach one end to the Black Line Screw (you can stack two wires under this terminal saddle if it is rated for it, or use a pigtail wire nut to feed both the switch line screw and the jumper). Attach the other end of the black jumper to the Brass Terminal Screw on the receptacle side. This ensures the outlet has constant 120V power.
  5. Connect the Switched Load (Black): Take the outgoing black wire that travels up to the ceiling light fixture. Connect this wire to the remaining Brass Terminal Screw on the switch portion of the device (often marked 'LOAD'). When you flip the toggle, this terminal receives power.
  6. Secure and Dress the Box: Carefully fold the wires into the back of the box. Push the grounds and neutrals to the back, and the hots to the sides. Drive the device mounting screws into the box ears. Use a torpedo level to ensure the yoke is perfectly plumb before fully tightening. Attach the faceplate.

Verify and Test: Meter Readings and Function Check

Do not assume the wiring is correct just because the light turns on. You must verify the receptacle wiring with a meter before plugging in expensive power tools or electronics.

  1. Restore power at the breaker panel.
  2. Set your digital multimeter to AC Voltage (V~).
  3. Test Receptacle Hot-to-Neutral: Insert probes into the hot (short slot) and neutral (long slot) of the outlet. Expected Reading: 114V to 126V. If you read 0V, your jumper wire (Step 4) is loose or missing.
  4. Test Receptacle Hot-to-Ground: Insert probes into the hot slot and the ground hole. Expected Reading: 114V to 126V. If you read 0V here but 120V hot-to-neutral, you have an open ground (check Step 1).
  5. Test Switch Function: Leave the switch OFF. Test the ceiling light fixture wires (if accessible at the canopy) or simply install the bulb. Flip the switch ON. The light should illuminate immediately. If the light flickers or hums, check for a loose connection on the Brass Load screw.

The Most Common Botch (And How to Avoid It)

When installing a light switch with outlet, the single most frequent mistake is failing to install the black jumper wire between the Line screw and the Receptacle Brass screw.

The Symptom: You flip the switch, and the ceiling light turns on. You plug a drill or lamp into the outlet, but it has zero power. Alternatively, if you mistakenly wired the incoming hot to the switch load terminal and the light to the line terminal, the outlet might only work when the switch is ON, effectively making the entire combo device a switched outlet (which defeats the purpose of a workshop drop).

The Root Cause: Many DIYers assume that because a standard duplex receptacle only requires one hot wire to feed both the top and bottom outlets (via the intact brass fin), a combo device will internally route power from the switch's line terminal to the receptacle's bus. On standard Leviton and Eaton combo devices, the switch and the receptacle are electrically isolated on the hot side to allow for maximum flexibility (like split-wiring or switching the outlet).

The Fix: Always treat the combo device as two separate devices sharing a single plastic yoke and a single ground/neutral path. The hot path must be manually bridged with a black jumper wire if you want an always-hot receptacle. If you have already closed up the wall and discover this mistake, de-energize the circuit, pull the device back out, and add the 6-inch black pigtail jumper. Do not attempt to bypass this by breaking the internal fins, as combo devices do not have break-off fins like standard duplex receptacles do.

For further technical specifications on combo device terminal layouts, refer to the Leviton 5241 official product documentation. For broader code compliance regarding receptacle placement and box fill calculations, consult the NFPA 70 National Electrical Code guidelines.