There are more than 50 million streetlights in the United States. From parking lots to park trails to bridges, these ubiquitous lights permeate our night lives and go largely unnoticed by the sustainability-inclined city dweller.
But this necessary technology comes with a whopping energy cost. A 2009 University of Pittsburghstudy shows most streetlights use high-pressure sodium bulbs (also referred to as sodium-vapor lamps), which emit a gaseous form of sodium in an excited state to produce light. Considered efficient, a typical sodium streetlight will use a 70- to 150-watt bulb, increasing to 660 w and 1,000 w for very tall applications.
In the past decade, however, energy efficient light-emitting diode (LED) lamps have hit the streets using, by comparison, 58 w to produce a better quality of light with less spillage.
A 2012 survey by Northeast Group LLC was published in October, claiming 95 percent of U.S. cities that have tried LED streetlights are satisfied with the results, saving nearly 60 percent in costs.
Yet, LED lighting currently accounts for only about 1 percent of the streetlights in the country.
The study shows what vendors and other proponents have been trying to prove since the beginning: the cost savings of LED technology are real and so are the benefits.
For one, LEDs emit a more directional, focused beam of light, making them particularly effective for streetlight and spotlighting applications. Where traditional lamps often produce significant spillover into the night sky above – contributing in places to unsightly light pollution – the directional nature of LED streetlights illuminates only the targeted area.
However, LEDs’ real benefit comes from their lengthy lifecycle. A sodium-vapor streetlamp is operational for 12,000 to 24,000 hours (depending on wattage). By comparison, an LED streetlamp has a lifetime of 50,000 hours. This contributes to cost savings in maintenance – fewer trips up the poles for workers. Fewer safety concerns associated with replacing bulbs at heights are an added benefit. In many cases reported in the survey, maintenance costs outweighed the electricity savings in a city’s decision to switch.
In the past, high upfront costs caused cities to need federal and state grant money to install energy efficient streetlights. While this trend continues, the survey proved that in almost all cases the lighting upgrades would pay for themselves in energy savings before the end of a streetlight’s lifetime.
The future of energy efficient and “smart” streetlight technology is uncertain. In many places, the government incentives are drying up, and some municipalities are simply unaware of the benefits. However, the results of Northeast Group’s survey show that among cities considering the upgrade, there are no longer significant concerns about public skepticism toward the new lights or about the durability or performance of LED streetlights.
The push to develop a nation-wide smart grid encourages the energy efficiency trend to continue throughout the decade. If Northeast Group’s survey results hold steady, we are on our way to zipping around streets nationwide that are becoming a little bit greener and safer, one light at a time.
Photo by Fotolia/Cozyta
Diagram courtesy Allen Linroman