A dimmer switch

Yes, modern electronic dimmers save energy. Furthermore, a dimmer that’s used to control a frequently used light will almost certainly pay its own way.

Dimmer switches save energy by switching the light on and off 120 times a second, which reduces the energy moving through the circuit. The longer the switch is off, the lower the light output and the greater the energy savings. To accomplish this, the switch uses a semiconductor device called a triac (triode alternating-current switch).

Buy the best quality dimmer switch that you can find (it shouldn’t break the bank). These switches are more durable and energy efficient than inexpensive dimmers, and their electronic circuitry eliminates radio frequency interference that can occur when a dimmer is used on the same circuit with electronics such as an AM radio.

Although switches are comparatively simple devices, there’s more to dimmer switches than meets the eye, says Al Lombardi, director of engineering for Leviton Integrated Networks and Controls, who provided a few pointers for us.

First, match the dimmer’s wattage rating to the load. For example, control no more than 600 watts of lighting with a 600-watt dimmer. The exception is when you “derate” the switch (restricting its use to less than its full wattage). Derating is necessary when you need to break off a dimmer’s cooling fin in order to fit the switch in a box with other dimmers. Without the extra cooling surface area, and in proximity to the other dimmers, the switch operates at a high temperature and cannot be used at its full wattage rating. Consult the manufacturer for derating instructions.

Next, match the dimmer to the type of load, such as incandescent or low-voltage lighting.

Also, don’t use a dimmer switch to control a ceiling fan; rather use a fan motor control or choose a dimmer/motor control combination device. And never use a dimmer to control power to an outlet or on a circuit with a shared neutral (the grounded conductor).