Lucalox High Pressure Sodium HID Outdoor Light Bulb is ideal for Motion-Sensing and Security. HID (High Intensity Discharge) lamps provide high efficacy and low operating cost. The HID is generally the most efficient light source. Better efficiency almost always means lower operating cost. They also have a long life. Most HID lamps have life ratings that are better than incandescent lamps and similar to fluorescent lamps. An HID lamp produces high light output from a relatively compact source. Like incandescent, it is a "point" light source, which allows for good optical control. Light bulb efficiency is measured in lumens per watt (LPW). Rated life for HID lamp life depends on the number of hours per start. The combination of high efficiency and long life makes HID an ideal light source for many commercial and industrial applications.