Controls and Sensors

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Introduction

In California, lighting accounts for almost 40% of commercial electricity use and about 25% of home electricity use. As a nation, we spend about 25% of our electricity budget on lighting, or more than $37 billion annually. Switching, energy management systems (EMS), photocells, dimming and occupancy sensors are lighting controls that can offer tremendous energy savings.

Technology Options

Switching
Reducing your lighting levels will reduce your energy consumption. For best results, make sure to select a switching device that is compatible with the space, the tasks being performed there, and the light or groups of lights being controlled. Manual, elapsed time, bi-level and clock switches all offer simple yet effective ways to save lighting energy.

  • Manual switches for each space or task in a building often make sense in older buildings that only offer switching at the circuit breaker for large gangs of lights.
  • Elapsed time switches may be useful in areas of limited occupancy. The timer may be preset for a duration that matches tasks commonly performed in the space, saving energy.
  • Clock switches may be programmed to keep lighting turned on for predetermined periods.
  • Bi-level switches offer a way to reduce lighting levels by switching off part of a lighting fixture when lower lighting levels are needed. Bi-level switching is a valuable energy saving technique for demand response to a utility's variable-rate pricing structure. Bi-level switches may be used during high utility rate periods to save energy and utility costs. Some state codes require bi-level switching.

Energy Management Systems (EMS)
Energy Management Systems (EMS) are sophisticated building- or facility-wide systems that control the lights, heating, ventilation and air conditioning (HVAC) and other equipment to achieve energy efficiency and comfort. They function much like switches, but they are controlled by a central computer or central control panel. These systems can be expensive, but they can increase the manager's control over a facility's energy consumption and often can provide significant ongoing energy savings.

Photocells
Photocells turn off or dim lights when daylighting in the space is sufficient. Photocells are often used with outdoor lighting, but may be connected to lights near windows or under skylights. Typically, photocells are not as effective with indoor lights that are farther than 12 feet from an outdoor lighting source.

Dimming
"Daylight dimming" switches may offer appreciable energy savings for lighting near windows or skylights. "Step dimming" reduces lighting levels at fixed intervals, typically in two or three steps. Manual dimming may be appropriate for spaces where presentations or computer tasks are performed. Incandescent, fluorescent and high-intensity discharge (HID) lights all have different dimming characteristics; HID lighting is the least favorable. The three primary ways to dim fluorescent lamps are with low-voltage controlled ballasts, power-line controlled ballasts and panel-level controlled ballasts.

Occupancy Sensors
In rooms where the lights are frequently left on, or where rooms are left unoccupied for large periods during the day or night, an occupancy sensor can cut lighting costs by as much as 50%. For occupancy sensors, two technologies dominate: infrared and ultrasonic.

  • Infrared sensors detect temperature changes in a room, and work well if the entire room is within the sensor's field of view. When a change in heat is detected, the sensor switches the lights. The drawback is that infrared sensors have a range of approximately 15 feet, and therefore only work in small areas.
  • Ultrasonic sensors use high-frequency sound to detect motion. The sensors monitor the reflection pattern of the sound off objects in the room; when the pattern changes, the sensors switch the lights on. When the pattern does not change for a while, the sensors switch the lights off. The drawback to ultrasonic sensors is that they can be triggered falsely by objects in the room, such as window curtains that are moved by a breeze. These sensors have a greater range than infrared sensors and are best deployed in larger areas.
  • Dual-technology sensors use both infrared and ultrasonic methods, which make them more accurate and versatile. However, dual-technology sensors are more expensive.

See the residential Occupancy Sensors guide for more information.


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Efficiency Benefits

Lighting controls may lead to significant savings. According the U.S. Department of Energy's Federal Energy Management Program (FEMP), a large office space may realize 10% savings by simply installing timers. Using timers with daylight dimming (if available) may lead to nearly 50% savings in lighting energy. In rooms where the lights are frequently left on or in rooms that are left unoccupied for large periods of time, an occupancy sensor can cut lighting costs by as much as 50%. In a small, private office, an occupancy sensor can reduce energy use by almost 30%, shaving 100 kilowatt-hours (kWh) off annual energy consumption. In a large, open office area, energy use can be reduced by approximately 10%.

Manufacturers

The Illuminating Engineering Society of North America (IESNA) publishes a searchable, annually udpated directory of manufacturers. Go to the IESNA website and click on “Manufacturers” in the left navigation bar.

Purchasing Tips

  • Keep track of lighting use patterns. In a commercial space, track the activities in the building to see if lighting controls are appropriate.
  • Make sure the lighting control selected is compatible with the existing lights. Some lighting manufacturers may limit the application of lighting controls with their equipment.
  • Consult lighting professionals to learn about the best lighting controls for your home or facility.