How to Install a Dimmer Light Switch for a Relaxing Mood in Any Room

Single-pole dimmer light switch installed with cover plate

The Spruce / Kevin Norris

Project Overview
  • Working Time: 15 - 30 mins
  • Total Time: 30 mins
  • Yield: Install one dimmer light switch
  • Skill Level: Intermediate
  • Estimated Cost: $10 to $30

Installing a dimmer switch saves energy and creates a relaxing mood in any room. Dimmer switch wiring might seem intimidating, but it only requires four wire connections. For most do-it-yourselfers, installing a single-pole dimmer switch is a fairly simple task that takes less than 30 minutes.

Single-Pole Switch

A single-pole or one-way dimmer switch controls a light fixture or a series of connected fixtures from one wall switch.

How to Choose a Single-Pole Dimmer Switch

  • Wattage capacity: The dimmer switch wattage rating should match or exceed the demand. Universal dimmer switches rated to LED 150W are common. An LED bulb that puts out 800 lumens requires 13 watts.
  • Single pole or three-way: Dimmers typically can be used in both single-pole and three-way (two light switch) applications, but be sure to confirm this.
  • Bulb type: A universal dimmer can control both dimmable LED and incandescent bulbs. Do not use an incandescent dimmer for LED bulbs.
  • Switch style: Slide, rotary, toggle, or digital are common dimmer switch control styles. All do the same thing, so it's mainly a matter of personal preference.

Tip

Dimmer switches are mostly used for ceiling-mounted light fixtures, not for electrical outlets or ceiling fans.

Safety Considerations

Before working on any electrical wiring, always shut off the power and test for current using a voltage tester.

Watch Now: How to Fix a Hot or Buzzing Dimmer Switch

What You'll Need

Equipment / Tools

  • Non-contact voltage tester
  • Wire stripper
  • Wire cutters
  • Eye protection
  • Screwdrivers (Phillips and flat-head)
  • Needle-nose pliers

Materials

  • Dimmer switch
  • Wire connectors (wire nuts)
  • Electrical tape (if needed)

Instructions

Materials and tools to install a single-pole dimmer light switch

The Spruce / Kevin Norris

Instructions

  1. Choose a Dimmer Switch

    Purchase a dimmer switch based on the wattage demands and the types of lightbulbs. Total the wattages of the bulbs served by the switch. Purchase a dimmer switch capable of dimming either LED or incandescent bulbs or both types.

    Example

    A track lighting fixture has four incandescent 60W bulbs, for a total wattage demand of 240W. Use a 600W-rated dimmer to control these lights.

    Closeup of using a newly installed dimmer switch

    The Spruce / Kevin Norris

  2. Turn Off the Circuit Breaker

    Find the circuit breaker for the circuit controlling the switch and light fixture and flip it off. Rock the switch outward to turn it off.

    Circuit breaker turned off for light switch installation

    The Spruce / Kevin Norris

  3. Remove the Switch Cover Plate

    With a flat-head screwdriver, carefully remove the two screws holding the outer switch plate to the existing switch. 

    Switch cover plate removed with flat-head screwdriver

    The Spruce / Kevin Norris

  4. Remove the Switch Mounting Screws

    Unscrew the mounting screws on the existing light switch. Do not touch the screw terminals on the side of the switch or any wires.

    Mounting screws removed with flat-head screwdriver from electrical box

    The Spruce / Kevin Norris

  5. Test for Power

    Check each wire in the box with the non-contact circuit tester. Touch the tip of the tester to each screw terminal on the switch. In many cases, the tester will light up even if it is close to, but not touching, a live wire.

    Non-contact circuit tester checking power on wires

    The Spruce / Kevin Norris

  6. Disconnect the Circuit Wires

    Detach the wires by loosening the screw terminals on the side of the switch and pulling the wires free. If a ground wire is also attached, disconnect it from the green ground screw. Wire nuts, if any, can be screwed off by turning them counter-clockwise.

    Tip

    Clean up the wires by straightening out curled exposed ends. Mangled wires should be trimmed.

    Circuit wires disconnected from screw terminals on side of switch

    The Spruce / Kevin Norris

  7. Connect the Dimmer Switch

    Attach wires on the dimmer switch to the wires extending from the electrical box.

    1. Connect one of the black dimmer switch wires to the one black line-in wire (the live wire).
    2. Connect the other black switch wire (or red wire without a tag) to the one black load-out wire (the wire going to the light fixture).
    3. Connect the one green dimmer switch wire to the two bare copper box wires; twist all three together under a wire nut.
    4. Connect the two white box wires with a wire nut. These entirely bypass the dimmer switch. Some electronic dimmers will have a white (neutral) that will be connected to the two white wires.
    5. Ignore the tagged red/white striped dimmer switch wire for now.
    Switch Wire Box Wire  Action
    Black wire Black line-in wire Connect
    Black or red wire (without tag) Black load-out wire Connect
    Green Two bare wires Connect all three
    N/A Two white wires Connect
    Red/white striped (with tag) N/A Cap off
    Dimmer switch wires connected in electrical box

    The Spruce / Kevin Norris

  8. Cap Off the Red-and-White Striped Wire

    If the switch has an additional wire lead (usually a red-and-white striped wire), this wire is not needed for a single-pole installation. It is only used in three-way installations where two switches control a light. Cap off this wire with a wire nut, then wrap it with electrical tape.

    Red and white striped wire capped off with wire nut

    The Spruce / Kevin Norris

  9. Complete the Installation

    Carefully fold the wires and tuck them into the box. Screw the dimmer switch onto the electrical box by threading the mounting screws into the threaded openings on the box. As the screws tighten, the switch will nudge the wires deeper into the box. Make sure that the dimmer switch is completely flush with the box's outer edge, then attach the switch cover plate.

    Dimmer switch mounted to wall with mounting screws

    The Spruce / Kevin Norris

  10. Turn on the Circuit Breaker

    Go to the service panel and flip the circuit breaker back on. Return to the dimmer switch and test its operation.

    Circuit breaker switch being pressed in home service panel

    The Spruce / Kevin Norris

When to Call a Professional

As far as electrical repair projects go, replacing a dimmer switch is a relatively easy one. With any electrical repair, though, there is the potential for dangerous, or even lethal, shock. If you are not confident in your abilities, it's best to call in an electrician.

FAQ
  • How many wires go on a single-pole dimmer switch?

    On a single-pole dimmer switch, there will be a total of three wires that go on the switch. There will be two wires that attach to the circuit wires in the box. There will be a third green wire that attaches to the circuit grounding wire. The fourth wire (red/white striped) is not used.

  • Can you put a dimmer on a single-pole switch?

    Yes, you can put a dimmer on a single-pole switch if you want to control a light fixture from that one switch. In most cases, dimmer switches are wired the same way as a regular switch. So if you already know how to install a single-pole switch, you should be able to swap it for a dimmer switch.

  • Why are there two black wires on a dimmer switch?

    The two black wires are the hot (or live) wire that comes into the switch and the other black wire (sometimes red) that goes out to the light fixture.

  • Does a dimmer switch need 3 wires?

    A dimmer switch needs three wires for a single-pole switch: one black, one black or red, and one green (ground). The remaining dimmer switch wire (usually, red/white striped) is not needed for single-pole operations, so it is capped off.

  • What is L1 and L2 on a dimmer switch?

    L1 and L2 stand for "lines 1" and "2," and they supply power to electronics on the circuit of the switch. C or COM stands for "common," and it supplies power to the switch.

The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Lumens and the Lighting Facts Label. EnergyStar.