Lighting Controls

Installing lighting controls is one of the most efficient means of decreasing facility operating expenses. When lights are left on unnecessarily or areas are lighted excessively, energy costs increase. For instance, a storage room may be used only four or five times a day, but the lights stay on: employees with their arms full may not be able to turn the lights off or may simply forget. Occupancy studies have shown that individual offices have a vacancy rate of 30% to 60% during a normal business day, but the lights may be left on 100% of the time. Each hour that an unneeded light operates represents unnecessary expense. Listed below are some devices available to prevent this kind of waste.

Time Switches

Twist timers are ideal for storerooms and similar low-traffic areas. Twisting the timer turns the lights on for a preset amount of time; when time is up, the lights go out. (Note: Since people occasionally underestimate their stay in an area, do not install time switches where improper lighting would create a safety hazard.) Timers are available with preset time durations-e.g., a maximum of 15 minutes, 30 minutes, or longer. Other time switches that look like standard toggle switches can be adjusted to different settings with a screwdriver, or manually controlled in the bypass position.

Occupancy Sensors

Occupancy sensors are also ideal in areas where lighting or exhaust fans are often left on, such as a restroom. Three types of sensors are available: motion, heat and audio. The area to be lit and the types of surfaces in the space will determine which sensor is most effective.

The motion sensor keeps the lights on as long as there is movement. After motion has stopped (lapse time is adjustable), the detector switches the lights off. Heat sensors, which detect infrared radiation and audio detectors, which are controlled by sound, operate in a similar manner.


Photocells sense existing light and turn electric lights on when natural light levels are low; off when light levels are higher. They are especially good for outdoor or security lighting control, allowing the outdoor lighting system to adjust to changing seasons. If exterior lighting is needed for only a portion of the night, a photocell can be used to turn lighting on and a time clock to turn it off. Some photocells have delay mechanisms to prevent temporary cloud cover from turning the lights on. Using natural light whenever possible also helps save lighting costs. A photocell can read the light level in perimeter rooms automatically, turning portions of the lights on or off accordingly.