According to the Smart Outdoor Lighting Alliance (SOLA), 2015 was a “watershed year” for outdoor light-emitting diode (LED) lighting.


SOLA’s recently released “Smart Urban Outdoor Lighting Trends” report states LEDs make up more than 50 percent of all new public outdoor lighting fixtures sold, and this percentage continues to grow rapidly.


As SOLA predicted, LEDs’ cost-effectiveness has essentially eliminated older-technology high-pressure sodium (HPS) from new public lighting installations.


“With average LED roadway fixtures dropping from $155 in 2014 to $125 in 2015, HPS can no longer be considered an economically viable alternative for most new and retrofit installations,” the report states.


This change is due to the parity of fixture costs with HPS and the increased cost of relamping and higher operating costs associated with them. While some cities will continue to relamp and replace damaged HPS fixtures, it will be extremely difficult to justify group replacement of any public lighting with anything but LEDs, according to the report.


Typical luminaire efficacies for LED roadway fixtures now average 120 lumens per watt (LPW), with some reaching 145 LPW. In 2014, most LED fixtures were in the 80–90 LPW range.


“If this pace continues, we can expect average performance in the 150 LPW range by the end of 2016,” the report states. “LED luminaire efficacy now exceeds HPS by approximately 50 percent and may be doubled by the end of the 2016.”


However, another efficacy trend is emerging, as new LED chips close the gap between warm- and cool-white lighting.


“Just two years ago, the typical 3,000K–5,000K CCT [correlated color temperature] delta was about 25 percent,” the report states. “Today, it is closer to 10 percent. This will reduce the economic pressure to use cooler color temperature fixtures that are proving less popular with the public, produce more glare and skyglow, and are responsible for more ecological problems.”


These trends show that a convergence of factors will continue to accelerate the transformation to LED street lighting in the near future.


“As innovative financing options like Energy Service Companies (ESCOs) remove the capital cost obstacle, and as reduced fixture costs and operating expenses shorten the payback period, we should see more cities taking the plunge,” the report states.


However, no LED public lighting should be considered without a pilot installation that involves public feedback.


“The days when DOT staff makes lighting decisions without consulting the community should be over,” the report states. “Color temperature, lighting levels and dimming options should be demonstrated, and an experienced lighting design firm should be contracted to help manage the process.”