Lighting Terminology Glossary

Adaptive Lighting: Adaptive lighting means varying lighting levels as needed during peak and non-peak times to maintain safety and visibility while reducing energy consumption

Better Buildings Outdoor Lighting Accelerator: Cities participating in the Outdoor Lighting Accelerator will demonstrate practical and effective best practices to accelerate the adoption of high-efficiency outdoor lighting and improve system-wide replacement processes at the municipal level. Cities will work together and with U.S. DOE to drive analysis, secure funding and install outdoor lighting systems. In doing so, Partners will develop best practice approaches to system-wide upgrades as well as address issues that limit investment in high-efficiency technologies such as financing and utility tariff-rates. A state or region may also join in a collaborative and supportive role, working with three or more cities in its state/region.

CALiPER: The U.S. DOE launched the CALiPER (Commercially Available LED Product Evaluation and Reporting) program in 2006 to address a need for unbiased, trusted product performance information in the early years of SSL. CALiPER testing and analysis, conducted by accredited test labs using industry-standard test procedures, helped to discourage low-quality products and inflated manufacturer claims. As a result, there are far fewer exaggerated performance claims today, and product quality has vastly improved. Read more at

Circadian Rhythm: Biological rhythms that repeat approximately every 24 hours are called circadian rhythms. Light helps maintain the circadian clock, and researchers are working to better understand how lighting can support or disrupt circadian rhythms. 

Correlated Color Temperature (CCT): Indicates how warm/cool light is. CCT is measured in Kelvin (K). Higher values (>5,000K) indicate a cooler/bluer light color; lower values (<4,500K) indicate a warmer/more orange light color.

Color Rendering Index (CRI): Indicates the light’s ability to render colors across the spectrum.

Compatibility: The ability for devices to coexist in a system without corrupting, interfering with, or hindering each other’s operations.

Controls/Adaptive Controls: Light control allows users to regulate the level and quality of light in a given space for specific tasks or situations by integrating dimming, daylighting detection, networkability and task tuning. 

Design Lights Consortium (DLC): The Design Lights Consortium (DLC) drives lighting market innovation by providing information, education, tools and technical expertise. Since 2010, the DLC has administered the Qualified Products List (QPL), a resource that distinguishes high quality, energy efficient commercial LED products. Read more at

Fixtures: A light fixture (also known as a luminaire) includes one or more lamps, a fixture body, and a light socket.

High-pressure sodium (HPS): The most commonly used technology by municipalities today. They emit an orange or burnt yellow color. 

Illuminating Engineering Society of North America (IESNA): A membership-based organization that communicates information on all aspects of lighting, including the development of standards, guidelines and testing requirements.

Illuminance: Indicates the light intensity on a surface per unit area. It is measured in footcandles (fc). 1 fc = 1 lumen/square foot. 

Incandescent: The most outdated and least efficient street lighting technology available. They emit a warm yellow glow. 

Induction lighting: Transfers electric power via electromagnetic fields, rather than electrodes. It is one of the more efficient methods of transforming electric power into light. 

Interchangeability: Devices are interchangeable if they can be exchanged for each other, providing the same operations without the need for additional configuration.

Interoperability: Devices are interoperable if they can both work together and share a common defined set of information. Examples of communications protocols that address interoperability include: 0-10V, DALI, ZigBee, EnOcean, Connected Lighting Alliance, TALQ, and ANSI C137.

Kilowatt-hour (kWh): A measurement of electric energy use in thousands, calculated by multiplying wattage by the total time the fixture draws power (a 100 watt light bulb that is on for 10 hours uses 100 watts x 10 hours =1,000 watt-hours = 1 kWh).

Lamp: An electric lightbulb, whether LED, CFL, halogen, or incandescent.

LED Lighting Facts®: LED Lighting Facts® is a program of the U.S. DOE that showcases LED products for general illumination from manufacturers that commit to testing products and reporting performance results according to industry standards. Read more at

Light-emitting diode (LED), a.k.a. Solid-State Lighting (SSL): Provides directional light and has a longer life than other light sources. LEDs are also improving rapidly in terms of color quality, optical design, and thermal management. Costs continue to decrease for these very efficient fixtures. 

Luminaire: A lighting product including one or more lamps, parts and wiring.

Mercury vapor (MV): Replaced incandescent light fixtures in the 1950s and continue to be a widely used technology today. They are often characterized by a bluish-green tint.

Metal halide (MH): Commonly used lighting source that emits a bright white to bluish light. 

Municipal Solid-State Street Lighting Consortium (MSSLC): The U.S. DOE Municipal Solid-State Street Lighting Consortium shares technical information and experiences related to LED street and area lighting demonstrations and serves as an objective resource for evaluating new products on the market. Cities, power providers, and others who invest in street and area lighting are invited to join the Consortium and share their experiences. Consortium members are part of an international knowledge base and peer group. Members receive updates on Consortium tools and resources, receive the Consortium E-Newsletter and help steer the work of the Consortium by participating on a committee. Read more at

Qualified Products List (QPL): DLC publishes manufacturer and model identifying information, as well as verified tested performance or rated performance information for each product. These fields include: Manufacturer, Brand, Model Number, Luminaire Efficacy, Light Output, Power Factor, Correlated Color Temperature, CRI, Wattage, Dimming Information and Light Distributions (i.e., zonal lumen density, NEMA classification, and/or spacing criteria). Read more at

Retrofit: Replacing select components of a lighting system or product to save energy. A lighting upgrade can include any strategy that reduces the system's energy use.

Smart Lighting: Replacing select components of a lighting system or product to save energy. A lighting upgrade can include any strategy that reduces the system's energy use.

Uniformity: Describes how evenly light is distributed across an area.

Useful life: Measures fixture lifetime. For non-LED fixtures, the useful life is the length of time until the lamp “burns out.” For LEDs, this term is usually defined as the estimated time after which light output depreciates to 70% of its initial rating.

Volume Purchasing: Refers to purchasing lamps or fixtures in bulk—sometimes with other jurisdictions—to receive bulk discounts.