What is Daylight Harvesting and How Does it Reduce Energy Consumption?

what is daylight harvesting?

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With more and more businesses pushing for net zero carbon emissions, a range of innovative solutions for a sustainable built environment have come to the fore. Whether that’s building automation systems, indoor air quality monitors or occupancy sensors, there are plenty of impactful options for organisations to explore.

However, one that’s less talked about but gaining significant traction lately is daylight harvesting. Let’s take a closer look at this lesser-known method of decreasing energy consumption in the drive to net zero.


What is Daylight Harvesting?

When we talk about daylight harvesting in the context of smart buildings, we’re referring to the measurement of daylight to offset the amount of energy needed to light a space. The goal of daylight harvesting is to reduce energy consumption and thus decrease emissions. It’s that simple!

Daylight harvesting typically makes use of lighting control systems to automate the whole process, increasing or decreasing the amount of light needed in a space – whether that’s in offices, meeting rooms or entire buildings – in response to the availability of daylight. 

Another definition of daylight harvesting is slightly related, yet different. It’s the capturing of external light to illuminate indoor spaces. While this also helps to cut energy consumption, the daylight harvesting we’re focusing on here is the sensor-led process that feeds into lighting control systems.


daylight harvesting quote


Daylight Harvesting System Components

A daylight harvesting system consists of several components, and each of these components works in unison to measure the availability of natural light and reduce energy waste.

There are some clever calculations going on behind the scenes, using a blend of smart analytics and highly-accurate sensor data to determine the appropriate provision of artificial light.

Without going too deep into the numbers, it works like this; sensors positioned in a space measure lux levels, which is a standardised unit of light intensity, along with occupancy data and the composition of light. 

Using this combined information, lighting control systems are able to automatically dim or illuminate the space or shut off the lights when the space is unoccupied.

For example, if a meeting room in an office is exposed to natural light at certain times throughout the day, lighting control will automatically regulate the amount of artificial light in the room at that time. Perhaps it is not needed at all, in which case lighting control will kick in and set the artificial light accordingly.

The occupancy data component plays a big part in the process, too. If a room is not in use, artificial light will automatically switch off so no energy is wasted.

If a room is in use when artificial light is needed and then someone leaves without switching the lights off, lighting control can work on a delay timer, turning the lights off after a few minutes. This is all made possible by daylight harvesting sensors.


Beringar HX2 Occupancy Sensors


Daylight Harvesting Sensor

A daylight harvesting sensor is a device that measures the intensity of light in a space. Beringar’s smart sensor, for example, can detect illuminance, which is measured in lux, along with uniform daylight illuminance (UDI%). These two data points are then stacked up against daylight factor (DF%) and daylight autonomy (DA%) to determine the provision of artificial light.

Although the sensor can be connected to a lighting control system so that the operation of lighting is automated, it can also be used standalone. Even without being integrated into a lighting control system, daylight harvesting serves a vital purpose – the insights can be valuable for businesses who wish to understand their energy consumption.

For example, if the business notices a pattern of overuse or misuse in certain areas, it can implement plans to mitigate energy consumption and waste, such as encouraging employees to be more vigilant when it comes to switching off the lights.


Benefits of Daylight Harvesting

Daylight harvesting can provide many benefits for businesses that own or lease commercial real estate. Here are a few of the main benefits of daylight harvesting:

Cost Savings: The most obvious benefit of daylight harvesting is cost savings. By adapting the supply of light in a given space in response to the availability of daylight, businesses can reduce their energy costs significantly. In a recent case for Historic England, daylight harvesting in a building retrofitted with low-energy LED lamps saw consumption reduce from 4,211 kWh per year to 1941 kWh – a 54% reduction – leading to a carbon saving of 930 kg.CO2 per year.

Sustainability: Daylight harvesting is a great way to reduce energy consumption. While the cost-saving considerations are undoubtedly attractive, in the case of companies primarily focusing on their net zero goals, daylight harvesting is a tangible, measurable way to understand the impact energy consumption has on the carbon footprint of a building or a space.

Improved Health: We’ve talked at length about the importance of optimised light levels, especially in an office environment. It has been shown that too much or too little artificial light can negatively affect physical and mental health. Optimal lighting conditions reduce stress and eye strain, leading to increased productivity and fewer absences.



4 When combined with lighting control systems, this energy-saving technique can ensure that optimal lighting conditions are provided for building occupants, leading to significant improvements in occupant well being and tangible gains for the business.


If you want to learn more about daylight harvesting in your office, contact us for a demo.

Picture of Mark Sorsa-Leslie

Mark Sorsa-Leslie

A Chartered Surveyor with a passion for technology. Developed a range of computer applications to support my work in real estate in the UK and 5 business start-ups so far. Over the last 25 years I have developed solutions ranging from eLearning platforms to IoT sensors and have been the bridge between business people and technology people throughout my career.

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