Adjusting the intensity of your lighting changes the entire feel of a room. From dinner parties to nightly reading, you can have the perfect lighting for your space. Even without lighting and electrical experience, most DIYers can replace a standard switch with a dimmer by following electrical safety guidelines and a straightforward guide like this one. Keep reading to learn how to install a dimmer switch and decide what type of dimmer switch you need.
Electrical Safety
The most important part of learning how to install a dimmer switch is making sure you’re doing it safely. Before you dive head-first into this exciting project, keep a few important safety tips in mind. First off, you should never work on a live wire, aka one that currently has power flowing to it. Doing so can lead to electric shock and even house fires, potentially causing permanent and irreversible damage to you and your home.
Even after you turn off power to your switch, check it with a voltage tester and make sure you’re wearing rubber electrical gloves while working with wires, which can protect you if something unforeseen happens with the circuit.
If any part of you is hesitant about installing a dimmer switch, stop now anddon’t try to DIY this one. An electrician can quickly and safely install a dimmer switch for you, so take advantage of their services. Any extra cost is always worth it for your safety.
Choosing the Right Dimmer Switch
Before installing a dimmer switch, make sure to choose a dimmer that’s compatible with your fixture, wiring, and lightbulbs. Here are the main considerations when selecting a dimmer.
Compatibility With Light Fixtures
Most light fixtures are dimmable, but some dimmers are only compatible with specific types of light fixtures. If the type is not a match, the lights could flicker or not work altogether. Double-check the packaging or the description of your dimmer before buying it.
Compatibility With Light Bulbs
Halogen and incandescent bulbs work well with most dimmers, but check the label on the switch you’re buying to be sure. It's harder to find compatible dimmers for LED and fluorescent bulbs, so keep an eye out for dimmers that specifically function with those types of light bulbs if you have them.
Number of Switches
If you have two switches that operate your light fixture, such as one at each end of the hallway or room, you need a three-way dimmer. Choose which switch location you want to install the dimmer at, as you can only dim a light fixture from one spot. If you have just one switch for your light fixture, then use a standard single-pole dimmer.
Total Wattage
Count the number of bulbs in your fixture and add up the wattage, which should be listed on the base of your bulbs if you don’t still have the box. Make sure the dimmer can handle the total wattage.
Ceiling Fans
Many dimmer switches aren’t compatible with lights that have ceiling fans. You need a specific type of electrical switch and dimmer to ensure the dimmer doesn’t burn out the fan motor.
Neutral Wiring
If your home was built after 1985, you likely have neutral wiring, which is compatible with most dimmer switches. If your home was built before 1985, check to see if you have neutral wiring. You can either upgrade your wiring to neutral or choose a non-neutral dimmer (which comes with a bulb adapter).
Turn Off Power to the Light
Open your circuit breaker box and turn off the power to the area where your light is. This step is critical to ensure your safety. Confirm that the power is off by flipping the switch on and off or using a voltage tester.
Remove Existing Plate and Switch
Photo: Jose Luis Pelaez Inc / DigitalVision / Getty Images
With a flathead screwdriver, remove the light switch cover. Use a Phillips-head screwdriver to disconnect the switch from the box.
Gently pull the switch away from the wall. If there’s a bundle of white wires in the back of the wall box, leave them there. You can use a voltage tester to double-check that no wires in the box have a charge.
Remove Wires From the Old Switch
Look to see where the colored wires connect to the existing switch. Snap a photo so you can easily reference it later when you’re hooking up the dimmer.
If you’re replacing a three-way switch, locate the "COMMON" wire, also known as the C-wire. If there isn't one labeled with a “C,” look for the wire that connects to a different screw color. Tag this common wire with a piece of electrical tape so you can find it when connecting the dimmer.
Remove the wires from the old switch. Keep the wires separate by bending them to opposite corners of the box. The ground wire is the green or bare copper wire that's connected to the green screw. Remove that wire last. If you’re replacing a dimmer with another dimmer, unscrew the wire nuts around the switch wires and house wires.
Prep the Wires for the New Switch
Use needle-nose pliers to attach the wires to the dimmer in the same spots as your previous switch had them. Reference the photo you took in step 3 to be sure.
If any house wires (usually black, red, or white with black marks) are bent, use a wire stripper to cut off the twisted ends and remove 3/4 inch of casing from the ends of the wires. Connect the green-colored or bare copper ground wire from your dimmer to the green or bare copper wire in the wall box. Twist the ends together clockwise and cap them using a wire connector nut.
Here's how to install a single-pole dimmer switch (meaning you only have one switch to that light fixture) after you’ve prepped all the wires:
Connect each dimmer wire (typically black) to a house wire by gripping the wire ends with a pair of needle-nose pliers and twisting them together.
Tighten a wire nut over each pair of wire ends.
If a bare wire is exposed, unscrew the connector and untwist the wires. Clip the ends of the wires with a wire cutter, twist them back together, and re-cap the wires so that no bare wire is exposed.
Use a screwdriver and screws to mount your dimmer to the wall.
How to install a dimmer switch with three wires after you’ve prepared all your wires:
Connect the black dimmer wire to your C-wire. Remove the tag you made out of electrical tape.
Connect the two remaining dimmer wires to each remaining wire in your wall box.
Use a screwdriver and screws to mount your dimmer to the wall.
If you have solid copper wires, create a “c”-shaped hook at the end of the wire with pliers. Guide the hook around the screw located on the side of the dimmer. Tighten the screw to secure the wire beneath the screw.
Attach the Switch Plate
Gently fold the wires back into the outlet box to prevent them from coming loose or breaking. Tighten the screws to secure the dimmer to the electrical box.
Tighten the mounting screws to set your switch plate in place (or snap the switch plate adapter to the dimmer if it’s a screwless design). If your dimmer switch has a knob, take it off before attaching the plate to avoid damage.
Once your wall plate is secure, reattach your knob if you removed it in the last step. Then, turn on your power from the circuit breaker and test the dimmer to ensure it works properly. If your light doesn’t come on or won’t dim, turn the power back off and double-check your wiring. If your light still isn’t working, reach out to an electrician for help.
DIY vs. Hiring a Pro
Is it safer to hire an electrician for any electrical work? Yes. Is installing a dimmer switch a relatively safe DIY so long as you follow electrical safety protocols? Also yes. You don’t always need to have an electrician install a dimmer switch unless you want to update your wiring or you feel uncomfortable working with switches and electricity. If either of those is the case, you can hire a local electrician to take care of the task. The cost to replace a light switch with the help of a pro is $150 on average.
Frequently Asked Questions
You can install a dimmer switch on almost any light as long as the switch, bulb, wiring, and wattage are compatible. Check what kind of light you have, the type of light bulb, and the total wattage of the bulbs to ensure your dimmer is a match. You’ll want to choose a non-neutral wire dimmer if you don't have neutral wiring. Homes built before 1985 that don't have updated electrical systems may not have neutral wiring.
Adding a dimmer to a switch is not difficult. It involves removing the faceplate and wiring, connecting the dimmer to the wiring, and replacing the faceplate. The main steps are ensuring you have a compatible dimmer switch for your fixture, light bulb, and type of wiring and connecting the wires to the dimmer.
No, wiring does not need to be redone to get a dimmer switch, as they work with single-pole and three-way switches. Just ensure you choose a dimmer that is compatible with your wiring, fixture, and lightbulbs. Most homes built after 1985 have neutral wiring and work with almost all dimmers. If your home was built before 1985 and you don’t have an updated electrical system, you may have to use a non-neutral wiring dimmer.
Yes, you can use a dimmer switch with an LED fixture, but it must be a dimmer that is compatible with LEDs. Check the manufacturer’s information to ensure the dimmer works with LEDs, as not all dimmers are compatible with them. Many smart light switches accept LEDs, but be sure to read the details on the packaging.
