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catrina klee ledcity
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We would also be happy to advise you personally to find the ideal lighting solution for your application!
We look forward to hearing from you.

Make an appointment

Who would you like to send your enquiry to?

Would you like personalised advice?

catrina klee ledcity
julian wiederkehr ledcity

We would also be happy to advise you personally to find the ideal lighting solution for your application!
We look forward to hearing from you!

Make an appointment

Kontakt Overlay (EN)

This field is for validation purposes and should be left unchanged.

Would you like personalised advice?

catrina klee ledcity
julian wiederkehr ledcity

Your enquiry cannot be resolved?
Our customer service is there for you from Monday to Friday: 08:00am - 05:30pm

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catrina klee ledcity
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Blog Posts - 29. January 2025

Lighting efficiency through daylight sensors: What our study found

Energy efficiency is more important than ever. Rising energy costs, increasing environmental concerns, and stricter sustainability goals are driving businesses to find smarter ways to save energy. Daylight sensors for lighting systems have emerged as a promising solution – but how much energy can they actually save?

To answer this, we conducted a 10-month study across eight use cases using NOMUS daylight sensors, integrated directly into each light source. The results reveal significant energy savings and highlight the key factors that influence performance of such daylight sensors.

Why daylight sensors matter for energy efficiency.

Efficient lighting systems are essential in reducing energy consumption in real estate. Over the past decade, the focus has been on transitioning from inefficient lighting technologies, such as fluorescent lamps (FL), to LEDs. LED luminaires not only contain fewer harmful substances but also significantly outperform fluorescent lights in energy efficiency, achieving energy savings of 40–60% on average. However, with many buildings having already adopted LED technology, the next challenge is finding additional ways to maximize energy savings.

While LED lighting is inherently efficient, the greatest opportunity now lies in minimizing the duration of their operation. For instance, reducing the usage of an LED light from 20 hours to just 2 hours results in 90% energy savings. There are two main possibilities to reduce the operational time of lighting systems:

 

1. Motion Sensors

Controlling the operational hours of lighting through motion sensors is a proven method. These sensors automatically switch off luminaires in unoccupied spaces, ensuring energy is not wasted. The effectiveness of this approach is maximized when motion sensors are integrated directly into each light source rather than relying on centralized motion detectors. Such integrated solutions can achieve energy savings of up to 80%, as demonstrated by the Stampfenbach case study.
This video demonstrates, how sensor-based lighting leads to a reduction in lights being on without compromising user comfort.

 

2. Daylight Sensors

Another effective strategy is the use of daylight sensors. These sensors adjust the brightness of luminaires based on the amount of available natural light, reducing the reliance on artificial lighting. This approach not only saves energy but also aligns with sustainable practices by leveraging cost-free, natural light. Daylight sensors, like motion sensors, are most effective when integrated into individual luminaires. But how impactful is this technology in real-world applications? To answer this, let us first examine the study’s methodology before exploring the results.

How the study was conducted.

Over 10 months (January to October 2024), we monitored light output every 15 minutes, 24/7. We compared energy savings achieved with both motion sensors and daylight sensors versus how much would be saved using motion sensors alone, which is already a significant amount.

The momentary savings varied between 0% and 100% depending on the lighting state (based on the motion sensors) and daylight conditions measured by the daylight sensors. Here are some simplified examples to show how the savings change depending on different factors. For these examples, we are using a lighting state set to 100% if movement within 2 meters, 40% if movement within 10 meters, or 0% if there is no movement within 10 meters.

When movement is detected within two meters:

  • Bright sunshine: The light turns off completely since no artificial light is needed. → 100% energy savings.
  • Cloudy sky: The light dims to 30% brightness because some artificial light is still needed. → 70% energy savings.

When movement is detected within ten meters:

  • Bright sunshine: The light turns off completely since natural light is enough. → 40% energy savings.
  • Cloudy sky: The light dims to 30% brightness because some artificial light is still needed. → 25% energy savings.

When no movement is detected within ten meters:

  • Bright sunshine: The light stays off since no artificial light is needed. → 0% energy savings (the light was already off).
  • Cloudy sky: The light remains off, as no movement is detected to trigger it. → 0% energy savings.

 

The formula used for the momentary savings is:
(LightLevelWithoutDaylightControl – LightLevelWithDaylightControl)/LightLevelWithoutDaylightControl
The individual data points were averaged, weighted by the light level without daylight control.
oem_sensor_node_bild
The study utilized intelligent lighting technology from NOMUS, incorporating both motion and daylight sensors into individual light sources. These sensors can either be directly integrated into the lighting fixture or connected via a NOMUS sensor node, as shown in the image.

Results: How much energy could be saved?

Across the eight tested scenarios, daylight sensors delivered significant savings ranging from 4% to 65%, depending on the location and lighting conditions. Below are the key findings:

Offices

  • Use Case 1: 8% energy savings
  • Use Case 2: 5% energy savings
  • Use Case 3: 4% energy savings
  • Use Case 4: 15% energy savings
  • Use Case 5: 23% energy savings

Corridors

Outdoor Spaces

Key factors that influence daylight sensor performance.

Several factors influence how much energy daylight sensors can save:

  1. Lighting Requirements: some spaces, like offices, need at least 500 lux of brightness for productivity. Even with daylight, light sources may still need to operate at lower levels.
  2. Weather Conditions: overcast skies, storms, or low-light periods reduce natural light availability, limiting the ability of sensors to dim luminaires.
  3. Architecture and Building Design: the design of a space plays a critical role in daylight penetration.
    1. Large windows and skylights allow natural light to flood the space, maximizing energy savings potential.
    2. Light-colored walls, ceilings, and flooring reflect natural light, enhancing its reach and reducing the need for artificial lighting.
  4. External Barriers: factors such as blinds, nearby buildings, or environmental obstructions can block natural daylight, forcing luminaires to remain active even when daylight is present.
  5. Usage Patterns: Spaces primarily used during daylight hours benefit the most.

By understanding and optimizing these factors, building owners can ensure that daylight sensors operate at their full potential, delivering higher energy savings while maintaining occupant comfort.

Are daylight sensors worth it?

The results are clear: daylight sensors deliver measurable energy savings. Especially in bright spaces used during the day, the savings can be substantial. However, even small savings of 5% can make a significant financial impact.

Let’s consider a building with annual lighting energy costs of 100,000 CHF. Although 5% savings do not sound like much, they would translate into 5,000 CHF cost savings every year – and that’s just on top of savings thanks to movement sensors. In combination, savings of 60 – 80% are possible compared to other LED systems.

With NOMUS daylight sensors integrated directly into every light source, businesses can achieve energy efficiency without compromising comfort or productivity. From office buildings to outdoor spaces, this smart technology is paving the way for a brighter, more sustainable future.

Ready to learn how NOMUS can help you optimize the energy costs and CO2 consumption of your building portfolio?

Book a non-binding discovery call: