Lighting typically accounts for 20–40% of a commercial building’s electricity consumption. Daylight harvesting is one of the most effective strategies to reduce this significantly — often by 30–50% in well-glazed spaces.
How Daylight Harvesting Works
A KNX or DALI-2 lux sensor is mounted on the ceiling, measuring the total horizontal illuminance at the work surface. It continuously compares the measured lux level against a target set-point (e.g., 500 lux for a typical office) and sends dimming commands to the lights to compensate for changing natural light.
As the sun gets brighter during the day, the artificial lights dim down. As clouds roll in, they dim up. The occupants experience a consistent, comfortable light level — and energy is saved automatically.
Combining with Presence Detection
The real savings come when you combine daylight harvesting with KNX presence detectors. Lights dim to a maintenance level (e.g., 10%) when no one is detected for 10 minutes, then switch off entirely after 15 minutes. When someone enters, the lights instantly return to the target lux level.
Real-World Results
In a 1,000 sq.m. open-plan office we commissioned in Whitefield, Bangalore, the combination of DALI-2 constant light control and KNX presence detection reduced the annual lighting energy consumption by 43% compared to the previous on/off switching system.
Talk to us about designing a constant light control system for your next project.
