The Measured Energy Savings from Two Lighting Control Strategies

The energy-saving benefits of two lighting control strategies — scheduling and daylighting — were investigated at demonstration sites in two large commercial buildings. A continuously-dimmable lighting control system was installed at the Pacific, Gas & Electric Co. building in San Francisco and an on/off switching system was installed at the World Trade Center building in New York City. By automatically scheduling the operation of the lighting systems to conform with occupancy patterns, lighting energy consumption was reduced 10 to 40%. Several scheduling techniques were investigated and the influence of switching zone size on energy savings was examined. Using photo-electrically controlled lighting systems which switch or dim lighting in accordance with available daylight, the energy consumed for lighting in daylit areas was reduced 25 to 35%. The influence of clear and overcast conditions on the energy savings associated with daylight-linked controls is discussed.