Security lights have increased in popularity as more and more people move into rural areas. Mercury vapor lights were the standard for many years and have proved durable and satisfactory. High Pressure Sodium (HPS) lights were promoted primarily because they use considerably less energy. However, the experience with HPS lights installed by some electric cooperatives has been disappointing and frustrating. The perception of some consumers is that HPS lights do not provide enough light. In contrast to mercury vapor lights, which start out bright and gradually get dimmer over the years, HPS lights actually get brighter over the years. Common voltage fluctuations, such as from window air conditioners, can cause HPS lights to cycle off. Problems with both the HPS fixture and the lamp, combined with the brightness and cycling issues, have resulted in numerous customer complaints. The extra trips to replace fixtures and lamps have increased maintenance costs, and although data is difficult to verify, it is believed that the increased maintenance costs may offset the energy savings. Preliminary data also indicates that the life expectancy of HPS lamps may be considerably less than mercury vapor lamps. As a result, many utilities suspect they are losing money on HPS lights and need to increase rates to avoid subsidizing this product.

The initial problems with HPS lights involved both the fixture and the lamp. Better quality fixtures are now available, but problems with HPS lights still persist. These problems are believed to be the result of improper installation of the fixture, inconsistent lamp manufacturing quality, or rough handling of the lamp. A large IOU found that lamp failures were greatly reduced following training which stressed proper handling and installation, including installing the lamp as the last step in the process. To reduce customer complaints and problems some utilities have switched back to mercury vapor and others are offering customers a choice. A survey by one cooperative indicates that customers prefer mercury vapor over HPS by a 4 to 1 margin, mostly because they prefer the white color of mercury vapor compared to the yellow color of HPS.

The energy savings potential make HPS lights a highly desirable choice. However, based on the limited experience discussed here, there is a need for greater improvement in HPS installation standards and lamp quality. RUS borrowers with similar HPS experience should let manufacturers know their concern and insist on improvements.

If you would like more information or have any questions, please call Mike Norman, General Field Representative (Kentucky), at (606) 253-4653, E-mail: mnorman@rus.usda.gov.