|Many municipalities are weighing the benefits of both LEDs and high-pressure sodium (HPS) as they consider their street-light options. The Lighting Research Center’s National Lighting Product Information Program (NLPIP) formally performed an “apples-to-apples” evaluation of existing street-lighting technologies as detailed in its September 2010 publication Specifier Reports: Streetlights for Collector Roads.
Established by the Lighting Research Center (LRC) in 1990, NLPIP has helped lighting professionals, demand-side management providers, contractors, designers, building managers, homeowners, and other consumers find and effectively use quality products that meet their lighting needs.
The program has a demonstrated history of transforming the market and upgrading the quality, reliability, and energy-efficiency of lighting products by providing objective, third-party information to verify product performance compared to manufacturer claims.
As is the case with all NLPIP publications, Specifier Reports: Streetlights for Collector Roads was designed to tell a story in an objective way. The report was widely publicized [see links to LEDs Magazine articles under Related Stories at right], but many third-party summaries and interpretations were misleading, so hopefully this article will clarify a few key points.
To emulate the streetlight selection process used by typical specifiers, NLPIP purchased and analyzed eight LED streetlights that were recommended by manufacturer representatives as equivalent to an incumbent technology, namely a 150W HPS streetlight with a Type III distribution.
Much to NLPIP’s surprise, all six of the LED manufacturer representatives recommended streetlights with lower light output than the incumbent HPS technology. However, in order to most closely follow the typical specifier selection process, those were the street lights NLPIP purchased and evaluated.
NLPIP analyzed the pole spacing needed for the streetlights to meet a national roadway lighting standard for collector roads, ANSI/IESNA RP-8. NLPIP then compared the streetlights’ power demand and economic costs over a one-mile stretch of roadway.
The report concluded that, on average, the recommended LED streetlights could use up to 10% less power, however, their life-cycle costs were higher. The LED street lights recommended by the manufacturer representatives would cost more than twice as much to own and operate as the incumbent technology over the life of the streetlights, primarily because the LED street lights required narrower pole spacings to meet the recommended practice for illuminating collector roads, and the cost of the poles per mile dominated the life cycle costs.
A recent addendum to the original report examined LED street lights that could match the pole spacing provided by incumbent 150W HPS street lights. The results of the life cycle cost analyses are summarized in the chart below.
||Average life cycle cost per mile of recommended LED streetlights
||Average life cycle cost per mile (excluding poles) of the "higher power" LED street lights
|25,000 hours (6 years)||2.6X incumbent 150W HPS||2.3X incumbent 150W HPS
|50,000 hours (12 years)||2.1X incumbent 150W HPS||1.7X incumbent 150W HPS|
The results of these analyses reinforce the fact that specifiers need to evaluate all available products, regardless of the technology, to provide their customers, as well as society, with the greatest lighting value.
In many ways the LRC is grateful for the attention given to this report, because the overarching goal of NLPIP is to provide objective information to those specifiers. Without that attention, many specifiers would have remained unaware of these findings.
To meet the collector-road lighting criteria, NLPIP found that when compared to HPS, current LED street lights:
• can save a modest amount of energy, and
• usually have a greater life cycle cost, with or without the need for new poles
Also, be aware that manufacturer representatives may recommend street lights that are not equal in performance.
|Name: ramadas Posted: Thu, 16 Dec 2010 05:12|
|Life cycle cost for LED luminaire is not as high as indicated in the article. Request provide more data to comment further - like
1. Life of sodium luminaire considered
2. Energy tariff considered
3. Number of hours of use per annum, considered
4. Maintenance schedule considered
5. Cost of maintenance
6. Efficacy of sodium luminaire & LED luminaire
7. Is carbon credit benefit is taken in to account?
|Name: richard Posted: Thu, 16 Dec 2010 22:12|
|Outdoor lighting has one serious flaw; misdirection. The pouring of light by fixtures designed in the 1950's up into the sky, or into the face of drivers. What it means is that the light is being wasted and isn't being completely directed toward the ground where it is supposed to be. What good is using fixtures that cost 2-3x as much if they commit the same sins as the original ones? I suggest people look at cities like Tucson (because of astronomical observatories) and around airports for ideas on how to house outdoor lights, where those lights a shielded from wastefully misdirecting their energy. Light pollution is serious problem, with many negative consequences and must be addressed.
|Name: david lepage Posted: Fri, 17 Dec 2010 14:12|
|I do not believe this study is relevant in 2010 (or 2011 for that matter.) Even the new addendum, with tests performed on more recent luminaires, does not represent reality.
First, why opt for collector roads? 68% of roads are in fact Local (Rural and Urban) in the US while collector roads represent only 20%. It would have been more interesting, in my humble opinion, to do tests that cover local roads applications.
As for the performance and costs, I am certain that much better results could be obtained with higher quality luminaires.
I invite you to take a look at this blogpost. Disclaimer: I work for Philips and I wrote this blogpost. It represents my personal opinion.
|Name: jeff xiong Posted: Tue, 28 Dec 2010 04:12|
|LEDs may not be able to provide sufficient light to the collector roads with the same pole spacing for high pressure sodium lights, however, in the streets where is little traffic, the present technology of LED lights can meet the lighting demands.
|Name: john lumo Posted: Mon, 21 Mar 2011 07:03|
|In a recent energy efficient tender for residential road street lights for a retrofit of 125MV Luminaires in one of the largest cities in South Africa, an international firm of consulting engineers was appointed to carry out a 15 year life cycle cost evaluation . Technologies of all types were invited to tender. The evaluation resulted in the long life electronically ballasted 57W CFLs being the most optimal technology on offer. Over 15years the life cycle costing worked out at just over a third of the cost of the LEDs on offer.|
|Name: armando Posted: Wed, 27 Apr 2011 23:04|
|First the disclaimer I work for Empower Electronics (empowerelec.com). Second, it is my personal opinion that HPS is a very viable light source for roadways, especially highways. I understand that 80% of center-line miles are local and rural roads but they are not illuminated to the extent of collectors and highways.
HPS is a fairly efficient light source and with emerging digital technology (electronic ballasts) can reach efficacies equal to LED with probably a lower life cycle cost once all factors are considered.
|Name: mark bahner Posted: Mon, 21 Jan 2013 23:01|
|When considering the results of this study, it is important to note that the costs of LED lighting have historically been coming down according to "Haitz's Law" (the LED lighting equivalent to "Moore's Law" for computers).
Haitz's Law observes that the cost per lumen of LED lights have been coming down by a factor of 10 every decade, and that the flux per unit have been going up by a factor of 20 every decade.
Here is a website that discusses Haitz's Law and the implications for LED lighting:
In my mind, the implication of Haitz's Law is that LEDs will be the only street lighting fixture used in a decade or two.
Written January 2013. ;-)|