Dining room light on dimmer switch

Dimmer switches add flexibility to existing lighting. They also help you save energy, money while adding to the life of your light bulbs by reducing the amount of wattage emitted.

Installing a dimmer switch is an easy home improvement project that can be completed in about 30 minutes to an hour by simply following the instructions below.

Step 1: Decide Which Dimmer is for You

Replacing a simple on-off light switch with a dimmer switch gives you more options for bright and low-level lighting. But how do you know which kind of dimmer to get? You can buy a single-pole dimmer for a circuit with an outlet controlled from only one switch location, or a 3-way dimmer for a circuit with an outlet controlled from two switch locations.

You also need to make sure that the total maximum wattage allowed for all the light fixtures that will be controlled by a single dimmer switch does not exceed the maximum wattage rating on the dimmer. For example, if you have six lights, each rated for a maximum 100W lamp, you will need at least a 600W dimmer. In general, low-voltage lighting requires low-voltage controls. Most fluorescent lights, however, cannot be controlled by dimmers. Once you know the maximum wattage allowed, you need to choose from the various types of controls — push-on/push-off, rotate-on/rotate-off, knob, slide, touch-activated or toggle switch with slide.

Step 2: Turn Off Power

Turn off the power to the circuit you're working on at your home's main electrical panel. Find the right breaker and flip it to the "off" position. If you're not sure which breaker it is, turn off power to the entire house. Turn the light switch on to double-check that the circuit is off.

Safety Alert!

Whenever you are working with electricity, use extreme caution. Turning power off is the most important step and should never be skipped. Not only does it protect you from injury, but it also protects the dimmer switch from potential damage.

After turning the breaker off, tape over it with a piece of electrical tape to ensure that no one will turn it on while you're working.

Step 3: Remove Existing Switch

Unscrew the cover plate with a screwdriver and pop it off. Remove the old switch by unscrewing the screws on the top and bottom of the switch. Carefully pull the switch out of the box. To verify that power has indeed been shut off, touch one probe of a neon circuit tester to one of the terminal screws and the other to the metal outlet box, a white (neutral) wire, or a bare (or green) ground wire. Move the probe to the other switch terminal and repeat.

Safety Alert!

If you are changing a very old switch, wires may be loose or brittle. They may even disconnect, which is another reason to be certain the power is off.

Step 4: Disconnect the Wires

Disconnect the wall wires from the existing light switch. If you have a single-pole switch, there should be three wires: One black, one white and a separate ground wire. Depending on where the connections are made, either loosen the terminal screws or insert a small screwdriver into the rectangular hole adjacent to the wire. If you have a 3-way switch, one of the wires will be connected under a different colored screw or will be plugged into a hole in the rear of the switch labeled "Common." Tag this wire with a piece of electrical tape.

Use a wire cutter to trim off the excess bare wire that extends past the plastic insulation. Do this on every wire. Then use a wire stripper to strip off 3/8" of insulation. This will give you a clean piece of wire for the connection to the dimmer switch.

Step 5: Connect Dimmer Switch

If you're working with a single-pole circuit, take one wire on the dimmer switch and one wire from the wall box and hold them side-by-side. With needle-nose pliers, twist the exposed part of the wires together. Tighten a wire nut over the wires. Repeat with the other two wires. For a 3-way circuit, connect the dimmer's black wire to the wire you taped in Step 4. When all wires have been connected, bend them in a zigzag pattern so that they will easily fold into the wall box. Push the switch back into place. Tighten the two screws that hold it in position using a screwdriver. Install the new dimmer switch plate over the switch and screw it into place using a screwdriver.

Step 6: Restore Power and Test

Return power to the circuit and test the dimmer to make sure your installation was correctly done. If the dimmer doesn't work, turn off the breaker and double check your wiring connections.

Congratulations! You're done. Now you've added some flexibility to your home's lighting options.

Project Shopping List

Here’s what you’ll need to complete this project successfully.