How Much Money Do Light Sensors Save?

Light sensors are devices that detect ambient light and provide a corresponding signal indicating the light intensity in the surrounding environment. They are used in a variety of applications to optimize lighting usage, such as automatically turning lights on at dusk and off at dawn or dimming lights when sufficient daylight is available.

By automatically controlling lights based on occupancy and available daylight, light sensors can help reduce energy usage from artificial lighting, saving money on electricity costs. Lighting accounts for about 15% of total electricity use in commercial buildings, so the potential savings from using light sensors are significant. For example, lights that are left on when not needed can be automatically turned off by light sensors. Dimmers triggered by light sensors also reduce wasted energy by lowering electric lighting on sunny days. Overall, light sensors are a simple but effective way to incorporate energy efficiency into lighting systems.

Types of Light Sensors

There are several types of light sensors that can help reduce energy usage and costs in commercial buildings and homes:

Occupancy/Vacancy Sensors

Occupancy sensors detect motion in a room to determine if it is occupied. They automatically turn lights on when motion is detected and off after a set time when no motion is detected. Vacancy sensors operate in reverse – the lights are off by default, and turn on when motion is detected. These sensors are ideal for spaces with irregular occupancy like bathrooms, storage rooms, and hallways.

Daylight Harvesting Sensors

Daylight harvesting sensors measure the amount of natural light in a space. They communicate with lighting controls to dim or switch off artificial lights when sufficient daylight is available. These sensors can reduce lighting energy use by up to 80% while maintaining proper illumination. They work best in spaces with windows and skylights like offices, classrooms, and gymnasiums.

Dimming Sensors

Dimming sensors automatically adjust light output based on occupancy and/or daylight levels. For example, they may dim lights to 50% when a room is partially occupied, or increase lighting in the evening as natural light decreases. Dimming controls provide flexibility to adapt lighting to usage patterns and reduce energy waste from over-lighting.

How Light Sensors Save Energy

Light sensors help save energy in buildings in a few key ways:

Turn Off Lights When Not Needed through Occupancy Sensing

Occupancy sensors detect motion in a space and automatically turn lights on or off based on occupancy. This prevents lights from being left on in unoccupied rooms which wastes electricity. Occupancy sensors can reduce lighting energy use by 10-80% per area by ensuring lights are only on when needed.

Dim Lights Based on Natural Light through Daylight Harvesting

Daylight harvesting uses light sensors to detect the amount of natural daylight in a space. The system then automatically adjusts the brightness of the lights to maintain a desired light level as the natural daylight changes. This can reduce electricity use for lighting by up to 70% during daytime hours.

Automatically Adjust Light Levels through Dimming

In addition to daylight harvesting, dimming systems can be preset or programmed to automatically change light levels at certain times of day or night. For example, lights may be dimmed to half power after business hours. This provides added energy savings beyond daylight harvesting alone.

Financial Savings from Light Sensors

Installing light sensors can lead to significant financial savings for businesses and homeowners. By automatically turning lights on and off based on occupancy and ambient light levels, light sensors reduce electricity usage, resulting in lower utility bills.

Studies have shown that buildings equipped with light sensors can reduce lighting electricity usage by 30-70%. For a business that spends $20,000 per year on electricity for lighting, the installation of light sensors could save $6,000 to $14,000 annually on the utility bill. Over several years, the energy savings can offset the upfront cost of purchasing and installing light sensors.

In addition to the direct reduction in electricity consumption, light sensors also save on maintenance costs. Fluorescent and LED lights fail over time due to cycling on and off. By reducing the frequency that lights turn on and off, light sensors extend the lifespan of bulbs. Given that commercial light bulbs can cost $10-$50 each to replace, less frequent replacements provide additional cost savings for businesses and homeowners.

Case Studies and Examples

Many organizations have implemented light sensor systems and achieved significant cost savings. Here are some real-world examples:

Office Building

An office building in Chicago installed occupancy sensors and daylight harvesting sensors throughout its 100,000 square foot facility. The sensors automatically turn off lights when spaces are unoccupied and dim artificial lighting when sufficient daylight is available. In the first year, the building reduced lighting energy usage by 65%, saving approximately $68,000 in energy costs annually.

University Library

A university library in Texas retrofitted its stacks, study areas, and offices with vacancy sensors and photosensors. The light sensors led to a 55% decrease in lighting energy consumption. The university recouped the $120,000 sensor installation costs in less than 2 years through the $85,000 in annual energy savings.

Grocery Store Chain

A grocery store chain installed smart lighting systems in 130 locations. The systems combine motion detectors and light sensors to provide adaptive lighting. This reduced the chain’s lighting electricity costs by 60-80%. The company achieved a return on investment in just over 1 year and continues to reap substantial cost savings.

Cost Considerations

Installing light sensors in a building or facility requires an initial upfront investment, but this cost is usually recouped over time through energy savings. Here are some of the main cost factors to consider:

Sensor Equipment Costs: The sensors themselves can range in price from $10-$100 each depending on the type, size, features, and quality. Photocell sensors on the cheaper end can detect ambient light, while more advanced occupancy sensors also detect motion and body heat. In addition, there may be wiring costs to connect the sensors to the lighting system.

Installation Costs: Installing the light sensors properly involves electrician fees for placement, wiring, calibration, and integrating the sensors with the existing lights. This can cost anywhere from $75-$250 per sensor depending on system complexity and electrician rates.

Integration Software: Advanced lighting automation systems often use software platforms to monitor and control the sensors. Integration software can cost $500-$5,000 for perpetual licenses depending on the number of sensors.

Mapping & Planning: Properly planning where to place light sensors and how to group them requires mapping the facility and doing a lighting analysis. Consultant fees for system design and placement recommendations often range from $1,000-$5,000.

Maintenance: While light sensors are generally low maintenance, periodically checking for dust buildup, alignment, and calibration is necessary. Annual maintenance contracts typically cost around $100 per sensor.

The total upfront cost of a light sensor system can seem high. However, given the energy savings and longevity of these systems, the investment often pays for itself in 1-3 years. The financial savings then continue to accumulate from lower electricity bills thereafter.

Non-Financial Benefits

In addition to financial savings, light sensors provide important non-monetary benefits for buildings and occupants. Automated lighting can enhance safety by ensuring spaces are well-lit when needed. Sensors will turn lights on when occupants enter an area, providing visibility and reducing the chance of accidents. In large buildings, emergency lights can be triggered by sensors to illuminate escape routes and exits. Motion sensors also support security by activating lighting when intruders are detected.

Greater energy efficiency from light sensors contributes to sustainability. By preventing lights from staying on unnecessarily, sensors reduce electricity use and environmental impact. This energy conservation helps businesses and organizations meet green building standards and corporate social responsibility goals.

Occupant comfort and productivity can also improve with light sensors. Automated systems create the right light levels for the task at hand and adjust for changing daylight availability. Office workers, students, and other building users benefit from appropriate illumination for reading, computer work, or other visual activities. Tailored lighting enhances focus and prevents eye strain. Sensors also allow personal control over the lighting in a workspace or other area. Overall, light-level optimization from sensors can support visual acuity, circadian rhythms, and occupant satisfaction.

Implementing a Light Sensor System

Installing an effective light sensor system requires careful planning and implementation. Here are some key steps:

Audit lighting usage patterns and needs. Conduct a thorough assessment of how different spaces are utilized and when. This will help determine optimal placement of sensors. Areas with sporadic occupancy like hallways and bathrooms should have motion sensors, while spaces with more consistent use like offices may benefit from occupancy sensors.

Choose appropriate sensors and positions. Select the right types of sensors (occupancy vs. motion, range, etc) for each space. Make sure they are positioned to accurately detect activity without false triggers. Consider ceiling mounted sensors for large open areas and wall mounted for smaller spaces. Avoid sources of electrical interference.

Consider zoned vs whole building approach. You can implement sensors per room or zone for the most granular control. Or install sensors to control lighting for the entire building. Zoned control provides maximum energy savings but at higher upfront cost. The whole building approach is simpler and more affordable, but savings may be less.

Work with a lighting specialist. Consult an expert in lighting and sensor systems to ensure optimal placement and functionality. Proper implementation is key to realizing the full energy and cost savings potential.

Challenges and Limitations

While light sensors offer significant energy and cost savings, implementing them does come with some challenges and limitations to be aware of.

One challenge is the complexity of initial setup and calibration. Properly configuring light sensors to match occupant needs and workflows while maximizing efficiency requires careful planning and adjustment. Maintenance staff may need training to properly calibrate and adjust settings over time.

Light sensors also require occupant behavioral changes to achieve maximum savings. Employees will need to be conscious of light sensor zones and avoid inadvertently triggering lights. Simple adjustments like facing towards natural light sources can also boost savings.

Additionally, light sensors may not be appropriate for all spaces. Bathrooms, hallways, and high traffic areas often require lights to remain on for safety and accessibility. Light sensors likely offer the biggest savings opportunity in offices, conference rooms, and other frequently occupied spaces.

With proper planning, calibration, and occupant education, the challenges of implementing light sensors can be overcome. The energy and cost savings generally make the effort worthwhile for many businesses and organizations.

Conclusion

In summary, light sensors can achieve significant cost savings for homes and businesses. Installing occupancy or motion-detecting light sensors can reduce lighting electricity usage by 30-80%, with typical payback periods of 1-3 years. The financial savings depend on energy costs, the number and type of lights controlled, hours of operation, and the sensor technologies used. With energy prices continuing to rise, the return on investment from light sensors is increasing.

Beyond the direct energy cost reductions, light sensors provide other benefits. They can extend the life of bulbs by reducing usage. Automated lighting helps create an optimal visual environment tailored to occupants’ needs. And smart lighting technologies enable advanced capabilities like circadian rhythm lighting and integration with other systems. While sensors involve an upfront expense and may require adjustment, the long-term savings and flexibility make them a green investment that both reduces costs and improves lighting experiences.