In June 2024, the DesignLights Consortium (DLC) published a study that found that when it comes to maximizing energy savings and minimizing light pollution, owners looking to upgrade outdoor lighting do not have to choose one over the other.

“Light pollution” is an informal term encompassing skyglow, light trespass and glare. Skyglow is light emitted or reflected skyward to obscure a view of the stars. Light trespass is light emitted onto adjacent properties. Glare is high brightness that can impair or disable vision. In recent years, spectral emission and its effect on circadian health has become another concern, leading the American Medical Association to issue guidelines in 2016 that recommend 3,000K light sources.

What to do?

The Illuminating Engineering Society (IES) and DarkSky International published “Five Principles of Responsible Outdoor Lighting,” which states that outdoor lighting should be useful (light is produced because it is needed), targeted (directed only where needed), appropriate (not brighter or of a higher level than necessary), controlled (produced only when and in the amount needed) and using warmer shades of white light where possible. The DLC enhanced these principles by publishing seven strategies:

1. Use dimmable and control-ready outdoor lighting
2. Consult with the community and local experts
3. Use the right amount of light
4. Control the lighting to save energy and minimize light pollution
5. Control the lighting to respond to seasonal environmental changes
6. Control the light distribution
7. Minimize blue-violet emission

Municipalities across the United States have adopted light pollution ordinances. The IES and DarkSky developed a Model Lighting Ordinance, partly based on the TM-15 “BUG” method of rating outdoor luminaires based on backlight, uplight and glare. The LEED building rating system incorporates requirements based on these guidelines, while the WELL rating system includes a requirement for 2,700K–3,000K light sources. Unfortunately, many community ordinances were written by people with little lighting knowledge. The DLC analyzed more than 650 (mapped on the DLC website) and found numerous inconsistencies and references to outdated methods and terminology.

Responsible, efficient lighting

In recent years, DLC has taken a leadership role regarding this issue. Representing some 100 utilities and organizations that administer lighting rebate programs, DLC maintains qualified products lists (QPL), notably a QPL for solid-state lighting (SSL) products, of which about half are outdoor LED products. The majority of commercial lighting rebate programs require product listing to qualify.

In December 2021, the organization addressed responsible outdoor lighting by launching LUNA 1.0, a set of technical requirements mitigating light pollution, with products satisfying the SSL and LUNA technical requirements listed as a subset of the SSL QPL. The result is a publicly available list of outdoor LED products that save energy and promote responsible outdoor lighting. The DLC subsequently released a sample outdoor lighting ordinance that is strikingly elegant, with a set of design requirements that can be met by simply installing LUNA products.

With the proliferation of LED lighting, the technology available to provide responsible outdoor lighting is readily available. LED light emission is relatively easy to optically control. LEDs are inherently controllable through switching and dimming, and the efficacy divide between cool and warm light sources has blurred. Today, products providing responsible outdoor lighting are widely available, with more than 350 products listed as LUNA-qualified. In its most recent facilities standard, the General Services Administration added a requirement for designers to use LUNA-listed products for area, wall-mount and bollard lighting.

Theoretically, responsible lighting is possible without a trade-off for energy efficiency. The DLC tested this notion by conducting a study in which two common applications—perimeter, walkway and parking lot lighting at a high school, and streetlighting on a town’s main street—were modeled and analyzed using lighting and photometrically accurate design software. In each, the base condition was a traditional HID light source upgraded in two scenarios: 4,000K LED luminaires and 3,000K LUNA-listed LED luminaires. The LUNA products reduced light pollution in the streetlighting application, though energy consumption varied based on luminaire type and product. 

In the high school application, however, designing to lower light levels—eliminating overlighting and dimming lights after-hours—saved energy compared to the non-LUNA option while reducing light pollution more than the luminaire optics. 

Overall, the study demonstrated that addressing light pollution proactively in an outdoor upgrade can be cost-effective when energy savings are considered. DLC offers a free economic calculator that includes rebates and control strategies and compares multiple applications. Electrical contractors can learn more and access these resources here.

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