Thanks to new technologies and higher quality standards, outdoor lighting is significantly more economical and has the potential to be more environmentally friendly. The following information is provided to help you choose the best option for your outdoor lighting needs.
Solid-state light sources, such as light emitting diodes (LEDs), are rapidly becoming the most popular option for outdoor lighting. LEDs represent substantial advancements in lighting technology over high-pressure sodium (HPS) lamps most commonly used for outdoor lighting, as they are highly efficient and long lasting. Additionally, LEDs are not vulnerable to vibration or breakage like standard bulbs, making them well-suited for use in locations such as schools, sports complexes, and parking lots.
Control systems can maximize energy savings by automatically dimming or turning off lights based on time of day, traffic flow, and other factors. LEDs have the ability to be configured in control systems that are much more sophisticated than anything used previously with traditional lighting.
What to Consider When Looking to Purchase LEDs:
- Because LEDs have increased in their energy efficiency so rapidly in the past decade, it is difficult if not impossible to specify LED outdoor luminaires by their wattage. As a starting point for retrofit applications, LED outdoor luminaires should produce no more light output (in lumens) than the luminaires they will replace.
- Check third-party certifications to help assess a product’s quality. Look for Design Lights Consortium listed products or Energy Star® certified fixtures and bulbs, which offers a three-year warranty from the date of purchase of any ENERGY STAR LED fixtures and bulbs. Logos for these standards for qualified lighting products are located on specification sheets, which can be requested from lighting vendors, and on manufacturers’ websites.
- Investigate control systems to reduce unnecessary lighting. LEDs are compatible with advanced controls in ways that other technologies are not. The Design Lights Consortium lists control systems that have met their standards.
The following sections of this page summarize issues to consider when designing, replacing or upgrading outdoor lighting, and provide resources you can use to help implement effective lighting that minimizes negative impacts.
Section 1. General Outdoor Lighting Guides, Standards and Recommended Practices
Caption: A worker laying out a measurement grid to check conformance with standards.
Outdoor lighting serves multiple purposes, including safety, security, and visibility. It is important to address those purposes appropriately to avoid wasting energy or creating unwanted impacts on nearby properties and on the nighttime environment.
A key element of successful outdoor lighting is understanding how to use lighting technologies to serve the purposes of a given installation. Numerous organizations, including the Illuminating Engineering Society, have published guidelines and recommendations for outdoor lighting in a variety of applications. In addition, several codes and standards address when outdoor lighting is appropriate and how much energy it should use.
Section 2. Light Pollution Information and Mitigation
Outdoor lighting is a necessary, integral part of our society’s infrastructure. Unfortunately, light pollution can result when lighting is used when and where it is not needed. When purchasing and installing outdoor lighting, avoid:
- Sky glow – brightening of the night sky caused by outdoor lighting.
- Light trespass – an undesirable condition where unwanted exterior light is projected onto neighboring property.
- Glare – an overwhelming light that causes annoyance and can impair or reduce visual performance; glare can occur when outdoor lights project light in the “glare zone.”
Unlike other light sources which emit light in all directions, LEDs are a directional light source that is easily controlled and can be a solution to the issues identified above.
Caption: An illustration of useful light versus light pollution.
Strategies to Help Reduce Light Pollution at Night:
- Follow Dark-Sky Association recommendations. It is desirable that all outdoor lighting be International Dark-Sky Association (IDA) compliant in order to mitigate the impact of artificial light at night. Visit International Dark-Sky Association for a list of compliant products.
- Consider environmental zones and curfews. In areas particularly sensitive to light at night, use lower light levels and dim or turn off lights after 11:00 p.m. or midnight.
- Use the Outdoor Site-Lighting Performance (OSP) metric when designing outdoor lighting. The OSP metric assists engineers to use lighting software to limit all three components of light pollution during the design phase of an outdoor lighting project.
- Consider factors in the environment that may disrupt the light. For example, fixtures should be designed to avoid interference from debris that can reduce the light’s longevity or inhibit light output, such as dirt and insects.
Another resource to help mitigate the negative environmental impacts of light is the Model Lighting Ordinance (MLO), which was jointly published by IES and IDA to help communities to draft local requirements to limit light pollution.
Section 3. Outdoor Lighting Visibility and Brightness
Research has recently uncovered new information about the way people see at night. The human visual system operates differently at low light levels compared with daylight hours as it generally is more sensitive to shorter (cooler) wavelengths of light at night. Using this knowledge, engineers can design and choose lighting equipment that will improve human visual performance at night, make outdoor space appear brighter, and increase people’s sense of safety and security, while minimizing the negative consequences of outdoor lighting.
Caption: Light sources with different spectral characteristics used in parking lots at night. The lights in the left picture emit shorter wavelengths of light than those in the right picture. Lighting with greater short-wavelength content can provide peripheral visibility and perceptions of brightness at lower light levels than lighting with greater long-wavelength content.
The first step in selecting a proper light source is to determine the goals of a lighting installation, for example improving visibility for drivers to help them see objects entering the roadway such as other vehicles, people, or animals. There are guidelines that can assist in selecting light sources that will best meet the objectives while using the least amount of energy and reducing wasted light.
- Download a list of resources about visibility and brightness perception under outdoor lighting. [DOCX]
Section 4. Safety, Security, and Crime Prevention
An important reason for installing outdoor lighting is to significantly improve safety for drivers, pedestrians, and neighborhoods. Sufficient continuous lighting may be important for roadways and streets where traffic and pedestrians frequently interact.
Caption: The impacts, if any, of outdoor lighting on the incidence of crime are not well understood.
Outdoor lighting is essential for the security of neighborhood residents as people generally feel more safe in brightly lighted areas. While research varies on how effective improved street lighting is in reducing crime, people commonly prefer well-lighted areas as they are more aware of their surroundings and can identify potential threats from a distance.
Section 5. Outdoor Lighting Strategies, Tools, Codes, and Standards
As LED technologies have advanced rapidly in the past decade, outdoor lighting specifiers have been challenged by this evolution. Many organizations have documented outdoor lighting installations in parking lots, along streets and roadways, and in other applications to assist specifiers in taking best advantage of the benefits of LEDs and minimizing drawbacks.
At the same time, comparisons of LED and other incumbent lighting technologies on an apples-to-apples basis are important so that governments and property owners can select lighting configurations that will meet the needs of occupants of outdoor locations, whether they are drivers, pedestrians, cyclists or other users.
- Download a list of resources that describe outdoor lighting case studies and comparisons among LED and other lighting technologies. [DOCX]
Section 6. Outdoor Lighting Controls and Adaptive Lighting Strategies
Energy codes for commercial outdoor environments are moving towards increased requirements for lighting controls. Strategies include scheduling time clocks, dimming curfews, or use of occupancy sensors. Developments in solid state lighting (LEDs) enable reductions in light output, and therefore power demand, during hours when an outdoor space is not occupied.
Developments in wireless communication technologies (e.g., “connected lighting systems”) enable widespread adoption of adaptive lighting controls in outdoor environments. While energy-savings opportunities due to outdoor lighting controls are numerous, technology coordination can be troublesome. Various control settings can have a significant impact on energy savings, and potentially, occupant satisfaction. Some demonstrations have evaluated occupant feedback about outdoor lighting controls.