The U.S. Department of Energy has released a new report on the comprehensive street lighting restoration currently being undertaken by the City of Detroit, which includes transitioning the existing high-pressure sodium (HPS) sources to LED. Entitled Restoring Detroit's Street Lighting System, the report provides an objective review of the circumstances surrounding the system restoration, the processes undertaken and decisions made, and the results to date.

By mid-2013, the year Detroit declared bankruptcy, it was estimated that as much as half of the city's 88,000 installed HPS units were not in reliable operating condition. In addition to repair and replacement of most of the streetlights, much of the associated wiring and supporting electrical infrastructure also needed replacement, due to its deteriorated condition. The previous number of fixtures, which included alleyways and residential areas where the population has significantly decreased in recent years, was deemed excessive from a budgetary standpoint, so the new system will be limited to approximately 65,000 LED streetlights.

Among the report's conclusions:

• Compared to the old HPS system (assuming fully operational), the new LED system will cut energy use by 60%, saving about 46 million kWh a year, worth about $2.9 million.
• The resulting energy and maintenance savings are expected to more than offset the incremental expenditure for the LEDs, with a simple payback of less than 2.5 years from energy savings alone.
• The new lighting system is also expected to improve reliability and safety, improve resistance to vandalism, and decrease opportunities for theft.
• The new system generally delivers higher-quality illumination than did the previous system, but the quality of illumination in some residential neighborhoods has been slightly compromised, due to a selective removal of poles and luminaires that has left extensive distances between those remaining.

For complete details, download the full report from the DOE SSL website.