Do Dimmer Switches Save Money by reducing
energy consumption in your New Jersey home?

The answer to this question depends on the type of dimmer switch and how long ago it was manufactured. Thanks to advances in microelectronics, many but not all newer dimmer switches incorporate technology that actually does reduce energy use. Even some less expensive newer models, however, still use older technology that consumes the same amount of electrical energy whether the light bulb is bright or dim.

Older dimmer switches control light levels by means of a fairly simple device called a variable resistor. An ordinary, non-variable resistor is simply a material that doesn't conduct electricity very well and restricts the amount of current flowing through it. A variable resistor consists of a stationary length of resistor material and a movable contact arm that is very conductive. A slider or a circular knob moves the contact arm along the length of the resistor material. The greater the length of resistor material through which the current has to flow, the lower the voltage reaching the bulb and the dimmer the light.

This is a pretty simple concept but it has one big disadvantage. Just as your brakes slow your car by applying friction to the rotating wheels, a resistor restricts the flow of electrical current by applying the electrical equivalent of friction, which generates heat. As a result, any electricity not converted into light is instead converted into heat, which is why some dimmer switches feel warm or even hot to the touch. In fact, when the dimmer is set at its lowest level, the current is passing through the maximum length of resistor material and thus generating the maximum amount of heat!

More modern dimmer switches operate on an entirely different principle. The electricity in your home is AC, or Alternating Current. That means it is constantly changing direction from positive to negative voltage. Instead of doing this in an abrupt, “on-off” fashion, however, it does it in the form of a wave that flows from positive through neutral to negative, then back through neutral to positive. In the United States, it does this 60 times a second.

In modern dimmer switches, an electronic device shuts the light bulb circuit off every time the current reverses direction – that is, whenever there is zero voltage running through the circuit. This happens twice per cycle, or 120 times a second, much too rapidly to be detected by the human eye. The device turns the circuit back on when the voltage climbs back up to a certain level, which is set by the position of the dimmer switch's knob or slider. If the dimmer is turned to a brighter setting, it will switch the circuit on very quickly after shutting it off. The circuit is turned on for most of the cycle, so it supplies more energy per second to the light bulb. If the dimmer is set for lower light, it will wait until later in the cycle to turn the circuit back on.

This approach has two significant advantages. First of all, since no electricity is converted to heat, it actually does save energy. And second, unlike the variable resistor, it uses the least amount of energy when at its dimmest setting. It may cost a little bit more, but it will pay for itself in energy savings.