How to Wire Two Light Switches With One Power Supply

It is not uncommon for a circuit to be configured so that two wall switches in a single double-gang box control two different light fixtures. The essence of the wiring configuration is for one hot feed wire entering the switch box to be split so that it feeds both switches, which in turn feed hot wires in cables that lead out to two separate light fixtures. However, the actual look of the wiring in the box can vary, depending on where the switches are located along the circuit run.

A double wall switch.
Two wall switches mounted in the same wall box can control two light fixtures fed by the same circuit.

This overview describes in very basic terms what the wiring looks like in the simplest installation — where the circuit cable first reaches the switch box, then feeds out from there to separate light fixtures "downstream" from the switch box. The assumption here is that a circuit is being extended from an existing source, such as a receptacle outlet, to feed a double switch that will control two different light fixtures

Step 1 Shut Off the Power to the Circuit

Turn off the power to the circuit you'll be working on by flipping the reset lever on the circuit breaker to the OFF position at the main service panel. Check to make sure power is off by using a circuit tester. If you are using a non-contact tester, make sure it is operating correctly by first testing it on an outlet you know is live. When you are sure it's functioning correctly, test the receptacle outlet where you'll be extending the circuit to make sure the power is off.

Step 2 Install a Double Switch Wall Box and Run the Feed Cable

If you are extending a circuit from an existing receptacle outlet to power light fixtures wired through a double switch box, you will need to install a double switch box, then run NM cables from the feed outlet location to the switch box. Then you'll run additional cables from the switch box to wherever the light fixtures are located. In the example shown here, the box and cables are laid out on a work surface so you can clearly see the wiring configuration.

  1. Once the wall box is installed, begin by feeding the feed cable from the outlet location into the new wall box, as shown in the photo. In this tabletop demonstration, the first cable is from the power source — in this case, a receptacle outlet at the end of the current circuit run.
  2. Strip about 6 to 8 inches of outer sheathing from the NM cable, and insert it into the new wall box. Some boxes have self-gripping fittings that hold the cable securely. With others, you may need to install a cable clamp to grip the cable.
  3. Strip about 3/4 inch of the insulation from the end of each insulated conductor in the box — one white wire and one black wire.

Step 3 Run Cables from Wall Box to Light Fixture Locations

Run circuit extension cables from the new switch box to the light fixture locations; strip the sheathing as needed, and insert them into the wall box, as shown in this tabletop example.

In the example, the cable at the bottom is the feed cable entering the box "upstream" from the power source, and the two top cables will continue on "downstream" to the separate light fixtures. You will have a total of three cables entering the box — one feed cable, and two cables leading to separate light fixture locations.

Step 4 Attach Pigtails to the Switches

On each of the two single-pole switches, install a hot wire pigtail and a ground wire pigtail that will be used to attach the switches to the wires from the feed cable.

  1. Cut two lengths of black wire and two lengths of bare copper wire about 6 inches long. Strip about 3/4 inch of insulation from one end of each black wire.
  2. Form a C-shaped loop in one end of the black wires and hook it in a clockwise direction around the bottom screw terminal on the side of the switch. Tighten the screw firmly.
  3. Now attach the bare copper wire to the green ground screw terminal on the metal strap on the switch in the same way.
  4. Repeat this for the other switch, attaching both a black and a bare copper pigtail wire.

Step 5 Join the Ground Wires

Gather together all the bare copper ground wires and join them together with a wire connector. There will be a total of six wires — two pigtail wires attached to the switches, and three circuit ground wires, one for each cable entering the box.

For convenience, use a green wire connector to make this connection. Although not required by Code, the green color is a convention used by electricians to identify the connection as a ground.

Step 6 Connect the Hot Feed Wires

Join the two black pigtails and the black hot wire from the feed cable together with a wire connector. The example uses a push-fit connector, a newer style of connector that has excellent holding power. You could also make this connection with a traditional twist wire nut.

Step 7 Connect the Switches to the Light Fixture Wires

There is one remaining screw terminal on the side of each switch. Connect one of the black wires running from a light fixture cable to each of these screws. Form a C-shaped loop in the stripped end of the wire; wrap it clockwise around the screw terminal, and tighten securely. The hot-wire pathway is now complete, from power source cable, through the switches and on to the light fixture locations.

Step 8 Complete the Neutral Wire Connections

Now use a wire connector (either a push-fit connector or a twist wire nut) to join together the white neutral wires from each of the three cables. Note that there is no neutral connection directly to the switches. This is because switches operate along hot current pathways only, and don't require a neutral connection. The neutrals simply "pass through" a switch box.

Step 9 Complete the Switch Box Installation

Very carefully tuck the connected wires into the switch box, and then press the switches into the box and secure them by attaching the mounting screws. Attach the switch cover plate.

Step 10 Open the Outlet Box at the Feed Location

  1. At the outlet location that will feed the new switch/light fixture segment of the circuit, remove the outlet cover plate, then carefully pull the outlet receptacle out of the box, leaving the wire connections intact. In the example, there are wire connections made to two screws — one brass "hot" screw and one silver-colored neutral screw. This is because this receptacle is at the end of the current circuit run. If this was a middle-of-the run receptacle, there likely would be wires connected to both sets of screws on the receptacle — one set for "upstream" wires from the power source, and one set of "downstream" wires running further along the circuit.
  2. Feed the new cable from the wall switch into the outlet box, using one of the available knockouts in the box.
  3. Strip 6 to 8 inches of sheathing from each of those new wires, then strip about 3/4 inch of insulation from the black and the white wire.

Step 11 Connect the Circuit Extension Wires to the Receptacle

Connect the new circuit extension wires to the receptacle. In the example, this is easy because there are available screws on the receptacle. Just attach the wires from the circuit extension cable to the available screws — black wire to the darker screw terminal, white wire to the silver-colored screw terminal.

Step 12 Complete the Feed Hookup

  1. Attach a bare copper pigtail to the ground screw on the receptacle, and then join this pigtail to all the ground wires in the outlet box, using a wire connector.
  2. As you did with the switches, carefully tuck the wires and receptacle back in the box, and secure the receptacle cover plate.
  3. All that now remains is to install and connect the light fixtures at the far end of the circuit extension. Once that is done, you can turn the power back on and test your installation.