Occupancy sensors detect the presence or absence of people and turn lights on and off accordingly. Used properly, occupancy sensors can be a cost-effective tool for reducing the operating time and/or light output of lighting systems, cutting energy consumption, and—usually to a lesser extent—peak demand. They may reduce lighting energy consumption by 50 percent or more in some circumstances, but the savings for any given installation can be much less. Occupancy sensors sometimes yield smaller-than-expected savings due improper product selection, improper installation, unanticipated interactions with other building components, or failure to adequately consider utility time-of-use rates and demand charges. Users and utility demand-side management programs can maximize the performance and cost-effectiveness of sensor installations by considering these issues.