U.S. Department of Energy Energy Efficiency and Renewable Energy

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October 05, 2012
Q.

I am council member of small Va town that has investigated whether installing 4 solar  street lights in lieu of standard street lights on power company poles is economical alternative. Our town employees determined that even with an upfront cost of $7000.00 to pay local power company (Dominion Resources) to install a transformer along with operating cost of $12 per light per month that it would take 48 years for the solar to pay for  itself.

Is solar that inefficient or am I receiving bad information? Do you have someone in your organization that can confirm or give me an analysis of what I should be expecting for use of solar lights in lieu of street lights for small Va town? Really need your help to analyze if solar is a viable option especially when i can in effect subsidized the cost in this situation where a $7K transformer is need for normal electric lights. -James
 

SunShot Solar Outreach Partnership

The SunShot Solar Outreach Partnership has been tasked with helping accelerate adoption of photovoltaic (PV) solar at the local level by providing timely and actionable information to local governments.

A.

Solar street lights have a number of advantages including lower maintenance costs, lighting in emergency situations or during power outages, and avoided emissions. However, solar powered street lights do often have a higher up-front cost. Given that we don’t have your staff's financial analysis in front of us, it is not possible for us to evaluate the exact circumstances of your potential solar street light project. In general, however, solar street lights may be a viable option in many locations when combined with LED lighting technology. Solar PV is actually quite efficient at capturing and converting sunlight into electrons and the panels on solar street lighting provide plenty of power to run the street lights and in some cases provide addition energy back to the grid. The long payback you reported would not necessarily be due to solar PV “inefficiency” but rather the specific circumstances of your project including how much your electricity costs, whether or not the solar is powering LEDs vs. more inefficient lamps, how often the lights are used, and whether or not the lights are “net metered.”

There are also examples where street lights are not separately metered by utilities and therefore without a special rate designation, savings might not be realized on the energy saved and only on the maintenance costs.  Given the high up-front costs it may make more sense to convert the street lights to LEDs first and consider adding solar PV at some point in the future. LED retrofitting or conversion of street lights can have a payback of 5-years or less.  We would recommend following up with the solar street light company that provided your Town with a price quote and also reaching out to other communities that have successfully implemented solar street light projects. Here are a few useful links to additional information. 

Here is analysis of solar street lighting done for Federal Facilities Managers:
http://www1.eere.energy.gov/femp/pdfs/ssl_lighting_systems.pdf
Here is an example of a DOE funded solar street light pilot project in Alabama:
http://energy.gov/articles/solar-led-light-pilot-project-illuminates-way-alabama
In addition, there are numerous examples of LED retrofit programs:
http://www1.eere.energy.gov/buildings/ssl/gatewaydemos_results.html
Again, thank you for contacting the SunShot Solar Outreach Partnership via the Department of Energy's Solar Resource Center.

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