Automatic lighting controls can yield considerable energy savings. Occupancy and vacancy sensors ensure that lighting systems operate only when someone is using an area and can reduce lighting demand by more than half. These sensors are most effective in enclosed spaces that are intermittently occupied.

Daylight harvesting controls, applicable to interior as well as exterior areas, save energy by reducing electric lighting when daylight is available. These systems include photocells to measure light levels, relays to dim or switch electric lights, and controllers that determine when to adjust the lighting state. In existing buildings, daylight harvesting capability may be improved by modifications to lighting control zones by grouping areas with similar daylight conditions and space function.

Different types of controls are required for different space types (Resources: How to Select Lighting Controls for Offices and Public Buildings (energy.gov) and Lighting Controls | Department of Energy ).

The primary types of lighting controls are as follows: 

• Occupancy sensors automatically turn lights on when someone enters an area and automatically turn lights off when no occupants have been detected for a short, set period of time. Occupancy sensors are most appropriate for spaces with safety or security concerns, spaces where occupants often carry items and can’t easily access the light switch, spaces with no daylight, and spaces where switches are in difficult-to-access locations.
• Vacancy sensors detect when an area is vacant and turn lights off, but require an occupant to manually turn lights Vacancy sensors provide the highest awareness of energy use decisions and achieve the highest level of energy savings. They are recommended for most spaces, including open and enclosed offices, conference spaces, and restrooms.
• Photo sensors control lighting in an area based on the amount of natural light available. They can reduce lighting costs by 20% or more and can easily be combined with occupancy or timer controls (or both). Daylighting controls are best suited to exterior spaces as well as perimeter rooms and spaces with moderate to large windows or skylights that provide ample
• Timers are devices ranging from simple time clocks to advanced controls used to regulate lighting in large areas. If the building is shut down completely at night, a timer can ensure the lighting is turned off, leaving minimal lighting for security and emergency navigation, as required by life safety building codes and security
• Advanced controls are combinations of sensors, timers, and controllers to regulate an entire building (or large area) based on preset points. These controls can use photo sensors with dimmers (daylight harvesting for effective use of natural light), occupancy sensors, and timers to ensure that lights are off when not needed. As sensor technologies have evolved, combinations of different sensor technologies in single devices have increased reliability and reduced instances of false shut-downs.

Note that not all sensors are security-approved for all building locations. OBO has prepared guidance for developing and implementing an interior lighting control strategy (Resources: Lighting – Energy Efficient Lighting for Sustainable Development (unfccc.int)).