Security Lights – High Pressure Sodium or Mercury Vapor?

| 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: [email protected].
 

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