Glossary of LED Terms

Glossary of LED Terms

Confused by technical terms like Color Temperature and Luminous Efficiency? Not to worry: we explain each of those terms in detail below.


A watt is simply a unit of measuring electrical power (which, in turn, is defined as the rate at which energy is consumed). The higher the wattage, the more energy is consumed. LEDs have become popular alternatives to traditional lighting sources due to their lower energy usage and thus energy savings. For more details on watts, see What is the difference between a watt and a watt-hour?

Operating Voltage

A volt is a unit of electrical pressure running through a current. The LED bulbs listed here have an operating voltage of 90-277 VAC, where VAC refers volts (electrical pressure) of alternating current (AC). This is the actual voltage supplied to the bulb.

Operating Temperature

This is simply the surrounding temperature at which the LED bulb can operate when active. The range listed in the table above is -13° F to 149° F, meaning that the LED bulb can successfully operate under these relatively extreme cold and hot conditions. If the LED is fitted inside of a fixture, then the operating temperature of -13° F to 149° F refers to the temperature within that specific, enclosed environment.

One main consideration in the lifespan of an LED bulb is its operating temperature. Dissimilar to fluorescents, colder temperatures do not affect LED performance, though higher temperatures might. To keep your LED bulb at its ideal operating temperature, consider the following:

  • It is generally advised that the open space around the bulb is approximately four (4) times the bulb size within the fixture or application. If the open space around the bulb is limited, then the bulb could heat the surrounding air and reduce the life of the bulb.
  • If your fixture or application has an opening to allow warm air to ventilate, then higher temperatures should not be a concern.
  • As with anything that uses energy, if not in use, turn the LED bulb off. Allowing the bulb to cool off or rest is typically a good idea for periods where the light source is not needed.

Operating Humidity

The LED lamp’s operating humidity refers to the surrounding air conditions of the fixture. Humidity is the amount of water vapor in the air at a given location. The percentage range listed in our spec details shows the recommended humidity, usually between 10 and 90%, in which the LED can perform optimally. As long as the surrounding air is not too dry or too wet, the LED lamp will function at its optimum level. Any location with a humidity percentage below or above the given range is not recommended.

Power Factor (PF)

Defined as the “active power” divided by the “apparent power” (or, put another way, the product of the rms input voltage and rms input current of a driver). The active power is the real power transmitted to the lamp, which is transformed into light (mechanical power). The root-mean-square (rms) refers to the most well-known mathematical process of defining the effective voltage or current of an AC wave. In a circuit where the applied rms voltage is Vrms and the circulating rms current is Irms, the apparent power S (kVA) is the product: Vrms x Irms. The apparent power is the basis for an electrical equipment rating.

Power Supply Efficiency

Power supply efficiency is the amount of power provided to the unit, divided by the amount of power drawn at the wall. So, a 50% efficient power supply that must provide 50 watts of power has to draw 100 watts from the grid to provide the required wattage to the unit. The extra 50 watts is lost as heat as this percentage of efficiency.

A 90% efficient power supply would draw about 62 watts in the same circumstances, with 6 watts being lost as heat. Our LED corn lamps operate at a 95% power supply efficiency or greater, meaning that a 56 watt LED will draw no more than 59 watts to operate.

LED Luminous Flux (lm)

According to the lighting definitions found here, luminous flux is “the quantity of the energy of the light emitted per second in all directions. The unit of luminous flux is lumen (lm).” In layman’s terms, this is the amount of light radiated by a light source per second. Luminous flux specifies the total amount of light radiated by lamp, but not the directions in which the light is radiated.

Here is great video explaining luminous flux in detail:

Luminous Efficiency

Luminous efficiency is the perceived brightness of light as a ratio of the total luminous flux to total radiant flux of the source and is usually given as a percentage. It is a measure of brightness obtained by dividing the source's luminous flux by the consumption of its energy.

Note: Luminous “efficiency” is different from luminous “efficacy.” For a light source, efficacy defines how well it turns input power into the desired output, lumens. Efficacy is usually conveyed in terms of “lumens per watt.”

CRI (ra) - Color Rendering Index

The CRI or Color Rendering Index is a scale that measures a light source’s ability to accurately render all the colors of their spectrum compared to a familiar reference light source like incandescent light or natural daylight. CRI is rated on a scale from 1-100: the lower the CRI rating, the less accurately colors will be reproduced. Light sources with a higher CRI rating will render colors in their spectrum with greater accuracy.

To know more about CRI, we also recommend the following online articles:

CCT (Kelvins) - Color Temperature

Correlated Color Temperature (CCT) describes the light appearance provided by a light source. It is measured in degrees of Kelvin (K) on a scale from 1,000 to 10,000.

Just remember: the lower the color temperature, the warmer the light’s color. The higher the color temperature, the cooler the light’s color.

  • Usually, commercial and residential lamps have temperatures somewhere on a scale from 2000K to 6500K (as you will find with our LED lamps).
  • A lamp’s color temperature gives us an idea about the look and feel of the light produced: 6000 degrees K will be a cooler white like daylight, whereas 3000 degrees K will produce much warmer light. The lower the color temperature, the warmer the lighting.
  • A light source’s color temperature is assigned on the basis of correlated color temperature (CCT).

What does all of this mean? If you heat up a metal object, that object will glow. Depending on the temperature (in Kelvins) of the metal object, the glow will be orange (warm), yellow (natural), or blue (cool). A light source’s color temperature is designed to replicate the Kelvin temperature and corresponding color of the metal object’s glow.

Lens type

As you might guess, lens type simply refers to the type of lens housing the LED modules. The lens ensures that internal, basic insulated or live metal parts are not accessible to touch (see our Testing & Compliance section for more info). Our LED corn lamps use clear lenses.

Expected Life

The expected life of an LED lamp (or any light source) is the period of usage expected before the light source depletes and must be replaced. Our LEDs are projected to last up to 15 years under normal usage conditions and when installed under the supervision of a licensed electrician (view our warranty for more information).


L70 is a measure of LED lumen depreciation for its projected lifespan. It describes the brightness of an LED after 50,000 hours. After 50,000 hours of burning, the lights will be 70% as bright as they were when first installed.

Note that L70 is a meaningless term without the corresponding number of hours. Some manufacturers may list L80 or L90 at 50,000 hours. This means that after that period, the LED lamps will be 80% or 90% as bright as they were when first installed.

Note: be careful not to confuse L70 with LM79 and LM80 (described below in more detail).

For more on lighting lifespans, we recommend this Lighting Basics article from P-2.


LM-79 is an IES* document that prescribes the approved method for taking electrical and photometric measurements of SSL or Solid-State Lighting products. It covers total flux (light output), electrical power, efficacy, chromaticity, and intensity distribution.

* IES refers to the Illuminating Engineering Society of North America.


An IES document that prescribes the approved method for Measuring Lumen Maintenance of LED Light Sources. It applies to bare LED light sources and does not cover complete fixtures. The LM80 specification deals a lamp’s usable life.

Beam Angle

An LED lamp’s beam angle is simply the angle at which light is emitted from the given source. In more technical terms, it is the angle between the points on either side of the beam axis where intensity decreases to roughly half of its maximum illumination (see our diagram below).

The main points to note:

  • A wider beam angle distributes less intense or less concentrated light over a wider surface area.
  • A narrower beam provides more intense or more concentrated light over a smaller surface area.
  • For most indoor applications, a wider beam angle like the one shown in our diagram will be the norm.

Shown below is the beam angle for one of our 54w LED lamps. Note: the higher the ceiling or housing for your LEDs, the wider the beam angle over the ground area and vice versa.


IP Rating

IP stands for Ingress Protection. In an LED rated IP64, the 6 designates the level of protection from solids (on a scale of 1 through 6), and the 4 designates the level of protection from liquids (on a scale of 1 through 8).

Such a standard is designed to provide customers with more detailed information beyond vague marketing terms like "waterproof."

The 6 in IP64 also means that the material is fully protected from dust and other contaminants. The 4 means that the material is fully protected from splashing water against the enclosure from any direction, but not from direct jets of water or total submersion in liquid.


The connector describes the type of connection point for the light source. In the case of our LED lamps, the connector is a base type utilizing the E26 type. E27, E39, and E40 are also available but lead times may vary for customers who choose these base types.

Base Type (Edison E26, E27) / Mogul (E39) / Goliath (E40)

The base type depends on the nature of your application. For an indoor LED lighting application, the E26 base will be the standard. For street lights, the E39 Mogul base is required.

Here are some key points regarding base type:

  • The Edison E26 is the standard 120-volt American base.
  • The E27 is the European variant and is rated at 220 volts.
  • The number refers to the circumference of the base in millimeters. So, E26 is 26mm in circumference whereas an E27 base is 27mm.
  • Often customers want to know if E26 and E27 light bulb bases interchangeable. The answer is yes, they are.
  • An E26 bulb can fit in an E27 base and an E27 bulb can fit in an E26 base without any problems. The sockets and bulbs are interchangeable except for the voltage rating. An LED E26 bulb that is considered universal line-voltage can be used in both E26 and E27 sockets.*
  • The large E39 Mogul and E40 Goliath base are used on street lights and high-wattage lamps.
  • The E39 Mogul is the U.S. standard whereas the E40 Goliath is the European standard.

*Always consult a licensed electrician in your area when considering LED lamps for any application.

Heat Radiator

Our LED corn lamps use heat radiators made of anodized aluminum. This is the standard material for heat sinks in most LED corn lamps, as it is well suited to dissipating heat emitted from the bulb during use. Heat dissipation is crucial for any lighting application, so you should always verify that your LED lamp is equipped with a heat radiator.

Safety Compliance - cUL and UL

The Underwriters Laboratory (UL) seal indicates that a product meets certain standards that conform with insurance company requirements for safety. An LED bulb without this designation is not of high enough quality for insurance purposes and may be unsafe to use.

EMI/RFI compliance - FCC

EMI refers to Electromagnetic interference. It is known as RFI or Radio-frequency interference in the radio frequency spectrum. The product complies with FCC regulations specific to EMI/RFI.

Environmental - RoHS

RoHS is the acronym for Restriction of Hazardous Substances. RoHS, also known as Directive 2002/95/EC, originated in the European Union and restricts the use of specific hazardous materials found in electrical and electronic products. All of our LED Lamps comply with the RoHS standards. For more on RoHS, see this page.

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