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Watt Stopper/Legrand-funded study documents 52% more savings from adding manual controls to occupancy sensors

SANTA CLARA, CA. May 2009 – Watt Stopper/Legrand partnered with the California Lighting Technology Center (CLTC) to determine how much lighting energy can be saved by adding manual bi-level controls to occupancy sensing systems in private offices. Occupancy sensors alone save approximately 30%, as compared to traditional switches, and meet energy code requirements for automatic shutoff. CLTC researchers showed that combining the two control strategies results in up to 52% additional savings. Watt Stopper funded this research in order to develop controls that provide the best possible return on investment for building owners and incorporate the functionality preferred by workers.

The study focused on how manual bi-level lighting controls should be configured to provide the greatest energy savings and occupant satisfaction. It concluded that the best practice control scenario is to have one light level come on automatically based on occupancy, while the other remains off unless manually activated. Study occupants periodically took advantage of the bi-level controls to turn on the second level of lighting, or to turn off both levels, based on task needs and available ambient lighting, and enjoyed having control over their lighting. This solution saved 52% more energy than occupancy sensors without manual controls.

Researchers also calculated energy savings using manual-on and automatic-on control of both lighting levels. Manual control, where both levels remain off unless switched on, saved slightly less energy than switching one level on automatically – 46%, compared to 52%. This is because some occupants, when faced with having to turn lights on, did not consider the lighting level and simply turned both switches on. Automatic on of both levels, as expected, produced the lowest savings – 34%. While occupants sometimes turned off unneeded lighting, they were less likely to customize lighting levels when all the lighting came on automatically. However, these savings are still significant, and illustrate the benefits of adding a manual control option to an occupancy sensing system.

“This study indicates that there is still a lot of room for energy savings in new and existing buildings,” says Pete Horton, VP market development for Watt Stopper/Legrand. “If you are looking for lighting energy savings, combining manual bi-level controls with occupancy sensing appears to offer building owners one of the highest available returns on investment,” Horton concludes.

Watt Stopper/Legrand has a long tradition of research and education about lighting control best practices. This study provides lighting professionals helpful new data points for control specification. By funding a study conducted by an independent research organization, Watt Stopper/Legrand ensured that the results would be credible to building owners and consultants who want to make specification decisions based on facts in evidence. Click here to download a copy of the CLTC Bi-Level Switching in Office Spaces Project Report


Editorial Contact and Photos:
Rita Renner, Marketing Communications Manager
WattStopper | 2800 De La Cruz Blvd. Santa Clara, CA 95050
Direct Tel: 408-486-7526, Fax: 408-988-5373

About WattStopper:
WattStopper (, a Legrand group brand, is a leading manufacturer of energy efficient lighting controls for commercial and residential use. We help customers find convenient ways to save energy, meet green initiatives, and comply with energy codes with our comprehensive range of products, programs, and services. Legrand (, located in Limoges, France, is the world specialist in products and systems for electrical installations and information networks, offering solutions for use in residential, commercial and industrial buildings.