Smarter Lighting, Lower Energy Use: How Modern Lighting Controls Make Buildings More Efficient

Replacing older lamps with LED lighting is one of the most recognizable ways to improve a building’s energy efficiency. However, installing efficient luminaires is only part of the solution.

A high-efficiency light still consumes energy when it is operating unnecessarily or producing more light than the space requires. Modern lighting controls address that problem by ensuring that lighting operates at the right level, in the right place, and at the right time.

Today’s lighting-control systems use sensors, schedules, dimming, software, and building-system integration to reduce wasted energy while maintaining safe and comfortable illumination.

Moving Beyond the Wall Switch

Traditional lighting control depended primarily on occupants remembering to turn lights on and off. While the wall switch remains useful, it is not always an effective energy-management system.

People forget to turn lights off. Large areas may be controlled by a single switch even though only part of the space is occupied. Lights may remain at full output when daylight is available or when a lower illumination level would be adequate.

Current lighting controls automate many of these decisions. Instead of operating only in response to a person pressing a switch, lighting can respond to occupancy, vacancy, daylight, time schedules, utility signals, and information from other building systems.

The U.S. Department of Energy recommends combining efficient LED luminaires with strategies such as occupancy sensing, task tuning, and daylight-responsive dimming to produce additional energy savings.

Occupancy and Vacancy Sensors

Occupancy and vacancy sensors are among the most common lighting-control technologies used in modern buildings.

An occupancy sensor detects when people enter or remain within a space. Depending on its programming, the sensor may turn the lights on automatically, maintain the lighting while the space is occupied, and turn the lights off or reduce their output after the occupants leave.

A vacancy sensor generally requires the occupant to turn the lights on manually but turns them off automatically after the room becomes vacant.

These controls are especially effective in spaces that are occupied intermittently, including:

• Conference rooms

• Private offices

• Storage rooms

• Restrooms

• Breakrooms

• Classrooms

• Warehouses

• Electrical and mechanical rooms

Instead of operating continuously during normal building hours, the lighting operates only when the space is being used. Wireless sensors can also provide a practical retrofit option when installing new control wiring would be difficult or disruptive. Federal energy-efficiency guidance identifies occupancy sensors as a method of increasing savings by turning lights off or reducing their output when rooms are unoccupied.

Daylight-Responsive Controls

Buildings with windows, skylights, clerestories, or other sources of natural light may not need full electric-light output throughout the day.

Daylight-responsive controls, sometimes called daylight harvesting controls, use photosensors to measure the amount of available light. The control system then dims or turns off selected luminaires when daylight can provide part of the required illumination.

For example, luminaires near exterior windows may operate at 30 or 50 percent output on a bright afternoon while fixtures farther inside the building remain at a higher level. As the sun sets or clouds reduce the available daylight, the system gradually increases electric-light output.

This strategy reduces energy use without requiring occupants to continually adjust the lights. It can also reduce the heat produced by the lighting system, which may lower the building’s cooling load. The Department of Energy identifies the integration of high-efficiency lighting, advanced controls, and daylighting as an important part of designing zero-energy buildings.

Daylight-responsive controls are also an increasingly important part of energy-code compliance. ASHRAE Standard 90.1 has continued to strengthen provisions involving daylight-responsive controls, occupancy controls, and the thresholds that determine where automatic controls are required.

Scheduling and Automatic Shutoff

Not every building operates on the same schedule. Offices may close at night, schools may have changing classroom schedules, and warehouses may operate different shifts in different areas.

Time-based controls allow lighting to follow the building’s actual operating schedule. A system can automatically turn lights off, reduce lighting levels, or place selected areas into an after-hours mode.

Modern schedules may account for:

• Normal working hours

• Weekends

• Holidays

• Seasonal changes

• Cleaning and maintenance periods

• Security operations

• Special events

Exterior-lighting systems may use astronomical schedules that automatically adjust for sunrise and sunset throughout the year.

After-hours overrides can allow employees to temporarily reactivate lighting in a specific zone without turning on the entire building. The system may then automatically turn the lights off again after a programmed period.

Task Tuning and High-End Trim

Many lighting systems are designed with more light output than is ultimately needed in the completed space. This may occur because of conservative design assumptions, changes in furniture placement, surface reflectance, work activities, or the selection of standard fixture packages.

Task tuning, also known as high-end trim, allows the maximum output of a luminaire or lighting zone to be set below its full capability.

A fixture may be capable of operating at 100 percent but may be limited to 70 or 80 percent during commissioning. Occupants can still use their dimmer through its full apparent range, but the programmed maximum prevents unnecessary overlighting.

The DesignLights Consortium identifies high-end trim as a major lighting-control strategy for reducing unnecessary energy use while preserving the illumination needed for the work being performed.

Task tuning is particularly effective with LED lighting because LEDs can frequently be dimmed without the dramatic reduction in efficiency or lamp life associated with some older lighting technologies.

Networked Lighting Control Systems

A networked lighting control system connects luminaires, sensors, switches, controllers, gateways, and software so that the devices can exchange information.

Unlike traditional systems, in which control zones are largely determined by branch-circuit wiring, networked systems can often be grouped and reconfigured through software. This makes it easier to adapt the lighting when walls, workstations, departments, or room functions change.

Current networked systems may provide:

• Occupancy and vacancy sensing

• Daylight-responsive dimming

• Scheduling

• High-end trim

• Individual luminaire control

• Scene control

• Energy monitoring

• Remote diagnostics

• Demand response

• Plug-load control

• Building-automation integration

The DesignLights Consortium’s current Networked Lighting Control requirements include capabilities involving occupancy sensing, daylight harvesting, continuous dimming, individual addressability, zoning, energy monitoring, external-system integration, remote diagnostics, and load shedding or demand response.

These systems give facility managers greater visibility into how lighting is operating. Instead of waiting for an employee to report a failed fixture or incorrectly operating sensor, maintenance personnel may be able to identify the problem through the control software.

Luminaire-Level Lighting Controls

Luminaire-level lighting control places sensors and controls at individual fixtures or small groups of fixtures.

In an open office, each luminaire may contain its own occupancy sensor, daylight sensor, controller, and network interface. When an employee occupies one workstation, the fixtures in that immediate area can increase their output while lighting in vacant areas remains off or dimmed.

In a warehouse, lights can respond as employees or equipment move through aisles. In parking structures, fixtures may remain at a reduced level until vehicles or pedestrians are detected.

This creates more precise control than operating an entire room or floor as one large zone. It also allows future zones to be changed through programming rather than extensive rewiring.

Integration With HVAC and Other Building Systems

Modern lighting controls can contribute to efficiency beyond the lighting system itself.

Occupancy sensors distributed throughout a building can provide information to the building automation system. When a room has been vacant for a specified time, the system may reduce ventilation, adjust temperature setpoints, or place nearby equipment into an energy-saving mode.

Lighting controls may also be integrated with:

• Automated window shades

• Heating and cooling systems

• Plug-load controls

• Security systems

• Room-scheduling systems

• Energy-management platforms

• Utility demand-response programs

Automated shades can admit useful daylight while controlling glare and solar heat gain. The lighting system can then dim the electric lights based on the available daylight. Research highlighted by the Department of Energy has shown that integrating lighting controls with automated shading can provide additional lighting and cooling-energy benefits.

Demand Response and Load Management

Networked controls can temporarily reduce lighting energy use during periods of high electrical demand.

A utility, microgrid controller, or building energy-management system may send a demand-response signal requesting a temporary load reduction. The lighting system could respond by reducing selected fixtures from 100 percent to 80 percent output.

The change may be barely noticeable to occupants, but when it is applied across a large building or a group of buildings, it can produce a meaningful reduction in peak demand.

Current networked-lighting standards recognize both one-way demand response, in which the system receives and follows a reduction command, and more advanced two-way arrangements that can report the building’s response back to the utility or energy-management platform.

Energy Monitoring and Analytics

A traditional lighting system provides little information about how much energy individual areas are using. Networked controls can collect operating data from luminaires, circuits, zones, or entire buildings.

Facility managers may use this information to:

• Compare actual use with expected performance

• Identify lights operating outside their schedules

• Locate areas that are consistently overlit

• Verify the results of energy-efficiency projects

• Detect failed sensors or control devices

• Compare performance across multiple facilities

• Prioritize maintenance and upgrades

Data does not save energy by itself. However, accurate information allows building operators to find problems and make informed adjustments instead of relying on assumptions.

How Much Energy Can Controls Save?

Energy savings depend on the original lighting system, operating hours, occupancy patterns, daylight availability, control settings, and quality of commissioning.

A building in which lights previously operated continuously will normally have greater savings potential than a building that already has effective controls. Warehouses, parking facilities, offices, schools, and other buildings with changing occupancy often offer significant opportunities.

A Department of Energy lighting initiative noted that installing lighting controls can save more than 30 percent of lighting energy in appropriate applications.

Individual projects may achieve higher savings. For example, a Department of Energy case study described facilities using networked occupancy sensors, daylight sensors, and continuous dimming that reported lighting-energy reductions ranging from 50 to 90 percent. These results were project-specific and should not be treated as a guaranteed savings level for every building.

Commissioning Makes the Difference

Advanced controls must be properly installed, programmed, tested, and maintained.

An occupancy sensor with poor coverage may turn lights off while employees are still working. A sensor with an excessive time delay may leave lights on long after everyone has departed. An incorrectly located daylight sensor may cause lights to dim too much or fail to dim at all.

Effective commissioning should verify:

• Sensor locations and coverage

• Occupancy and vacancy settings

• Time-delay settings

• Daylight-sensor calibration

• Dimming performance

• Control-zone assignments

• Schedules and holiday programming

• High-end trim levels

• Manual overrides

• Emergency-lighting operation

• Communication between system components

• Integration with other building systems

Facility personnel should also receive training, current system documentation, programming records, passwords, and backup files.

The job is not complete simply because every fixture turns on. The lighting must respond correctly under occupied, unoccupied, daylight, scheduled, after-hours, emergency, and communication-failure conditions.

The Future of Energy-Efficient Lighting

Lighting is becoming part of a larger connected-building strategy.

Future systems will increasingly use sensors, analytics, artificial intelligence, and building-performance data to adjust operation. Lighting networks may help buildings identify occupancy patterns, predict equipment problems, manage peak demand, and coordinate lighting with heating, cooling, shading, security, and renewable-energy systems.

However, the most valuable system is not necessarily the one with the greatest number of features. It is the system that is appropriate for the building, understandable to its operators, maintainable over its useful life, and properly commissioned.

Conclusion

LED technology has significantly reduced the amount of power needed to illuminate modern buildings, but lighting controls take efficiency further.

Occupancy sensors prevent lights from operating in empty rooms. Daylight controls reduce electric-light output when sunlight is available. Scheduling prevents unnecessary after-hours operation. Task tuning limits overlighting. Networked systems provide precise zoning, monitoring, diagnostics, and integration with other building systems.

Together, these technologies transform lighting from a fixed electrical load into a responsive building system.

For building owners, electrical contractors, designers, and facility managers, the goal is no longer simply to install efficient lights. The goal is to provide the correct amount of light only where and when it is needed—and to avoid using energy when it provides no benefit.