The Light Bulb Guide: LED - vs - CFL - vs - Incandescent
The recent introduction of LED light bulbs to the marketplace has many home owners asking questions about the
multitude of choices with light bulbs today.
When first introduced, the high price tags on LED bulbs was hard to fathom when we were, in the recent past,
accustomed to buying regular ol' incandescent bulbs for less than a dollar a piece.
However, as LED bulbs are truly becoming mainstream, the price has come down to a much more competitive level making
it quite clear other types of bulbs will soon become a choice of the past.
Not only has the government begun forceing the retirement of incandescent bulbs by regulation, CFL bulbs will soon
be phased out by legislation...and market driven forces.
In a recent article published on Feb 1, 2016 GE annouced they will be phasing out the production of CFL bulbs in
2016 and focus strictly on the production of LEDs
(read article here).
LED bulbs are here to stay...so you may do well to become more familier with them.
We found this light bulb guide below published by Waseca Utilities of
The Southern Minnesota Municipal Power Agency to be an excellent comparison of the various types of light bulbs on
the market today.
Namely: LED, CFL and Incandescent. We converted it into a graphic...but you can download the original .pdf version
Light Bulb Size and Shape Chart
Bulb Base and Filament Chart
All lamps have a specific "bulb type" designation
that describes the shape of the lamp and the size of the lamp
(diameter). The designation is a two part code consisting of a letter
and a number. The letter indicates the shape of the lamp and the number
relates to the diameter of the lamp in eighths of an inch.
The reference ruler at left illustrates the most
commonly used household lamp, an A19. The "A" indicates the shape
(standard) and the diameter would be 2.38", which is "19" eights of an
All lamp types are available in a variety of
technologies and therefore may vary in appearance. Maximum overall
length (MOL) will also vary.
Additional popular lamp designations are also indicated on the reference ruler. Here is a quick guide to
||Bulged, Bulged with angular tip
||Conical, Candel shape with bent tip
||Reflector, Pear shape
||Straight-sided shape (compare with CA and BA)
||Elliptical, Elliptical with dimple in the crown
||Parabolic Aluminized Reflector
Glossary of Bulb Terminology
AC (Alternating Current)
: Electrical current in which the direction is
reversed at regular intervals or cycles; in the U.S. the standard is 120
reversals or 60 cycles per second.
: The involuntary muscular process by which the eye changes focus from one distance to another.
: The involuntary process by which the visual system
changes its sensitivity, depending on the luminances prevailing in the
visual field. The process involves both the iris and the light sensitive
cells of the retina.
: A measure of electrical current. Amps = Watts (Power)/Volts (Voltage)
American National Standards Institute (ANSI)
: A consensusbased organization which coordinates
voluntary standards for the physical, electrical and performance
characteristics of lamps, ballasts, luminaires and other lighting and
: These are 3-letter codes assigned by the American
National Standards Institute. They provide a system of assuring
mechanical and electrical interchangeability among products from various
: Inert gas used in incandescent and fluorescent lamp
types. In incandescent light sources, argon retards evaporation of the
Average Rated Life
: An average rating, in hours, indicating when 50% of a
large group of lamps have failed, when operated at nominal lamp voltage
and current. Manufacturers use 3 hours per start for fluorescent lamps
and 10 hours per start for HID lamps when performing lamp life testing
procedures. The life of an LED is defined as the operating time in hours
for the lamp to reach L70 which designates 70% lumen maintenance (or
30% reduction in initial light output). Every lamp type has a unique
mortality curve that depicts its average rated life.
: The ballast is an auxiliary electrical device that
performs two basic functions: 1) provides the starting voltage and 2)
the current to sustain lamp operation. There are several types of
ballasts including Instant Start, Programmed Start, Pulse Start and
Rapid Start (see definitions).
: The percentage of a lamp’s rated lumen output that
can be expected when operated on a specific, commercially
available ballast. For example, a ballast with a ballast factor of 0.93
will result in the lamp’s emitting 93% of its rated lumen output. A
ballast with a lower BF results in less light output and also generally
consumes less power.
: The beam angle defines the light pattern around the beam’s central out to the angle where the luminous intensity
(brightness) is half that of the maximum luminous intensity (CBCP - center beam candle power).
: The position in which a lamp is designed to operate in; this applies mainly to High Intensity Discharge lamps.
Capacitor - Device in ballast that stores electrical energy. Often used for power factor correction and lamp
CE (Conformité Européene)
: CE Marking on a product is a manufacturer's
declaration that the product complies with the essential requirements of
the relevant European health, safety and environmental protection
legislations, in practice.
: The measure of luminous intensity of a source in a given direction, regardless of distance.
Center Beam Candlepower (CBCP)
: The luminous intensity at the center of the beam of a
reflector lamp. Measured in candelas.
Chromaticity - Measure to identify the color of a light source,
typically expressed as (x,y) coordinates on a chromaticity chart.
: Refers to a lamp with a special phosphor or coating to give it a color rendering profile similar to natural
Color Rendering Index (CRI)
: A lamp’s ability to render an object’s true colors based on a scale of 100.
Correlated Color Temperature (CCT)
: A numerical measurement of the color appearance of a
light source measured in degrees
Kelvin (K). It also refers to the way color groups are perceived
(psychological impact of lighting). A low color temperature implies
warmer color (more yellow/red) light while high color temperature
implies a cooler light (more blue).
: A measure of the rate of flow of electricity, expressed in amperes (A)
DC (Direct Current)
: A type of electrical current and distribution by
which electricity flows in one direction through the conductor. Battery
operated systems are typical DC applications.
: A reflector (or filter) that reflects the visible
light region of the spectrum while allowing the other region(s)
(heat) to pass through the back of the lamp. A reflector lamp with a
dichroic reflector will have a "cool beam" since most of the heat has
: A light source that produces light by passing a current between electrodes through a vapor or gas. Includes
fluorescent and high intensity discharge lamps.
Department of Energy
: Governmental department whose mission is to advance
energy technology and promote related innovation in the United States.
: A self-contained power supply that has outputs which match the electrical characteristics of the lamp. It is
similar to a
ballast and is used to power illumination sources.
: A measurement of how effective a light source is in
converting electrical energy to lumens of visible light. Expressed in
lumens-per-watt (LPW) this measure gives more weight to the yellow
region of the spectrum and less weight to the blue and red region where
the eye is not as sensitive.
: The efficiency of a light source is simply the
fraction of electrical energy converted to light, i.e. watts of visible
produced for each watt of electrical power with no concern about the
wavelength where the energy is being radiated. For example, a 100 watt
incandescent lamp converts 7% of the electrical energy into light;
discharge lamps convert 25% to 40% into light. The efficiency of a
luminaire or fixture is the percentage of the lamp lumens that actually
comes out of the fixture.
Electrical Testing Laboratory (ETL)
: Independent testing laboratory that performs ballast tests and certifies accuracy of performance data.
: A continuum of electric and magnetic radiation that
is characterized by wavelength or frequency. Visible light encompasses a
small part of the electromagnetic spectrum in the region from about 380
nanometers (violet) to 770 nanometers (red) by wavelength.
Enclosed Fixture Rated
: See Open Fixture Rated.
Environmental Protection Agency
: The mission of EPA is to protect human health and
the environment. The EPA implements environmental laws written by
Congress through the development of regulations and their enforcement.
Energy Independence and Security Act (EISA) 2007
: The Energy Independence and Security Act of 2007 was
signed into law on December 19, 2007. The act builds on the progress
made by the Energy Policy Act of 2005 (EPAct) in setting out a
comprehensive energy strategy for the 21st century. This act is a major
step toward reducing our dependence on oil thereby increasing our energy
security and making our country cleaner for future generations. An
update was issued in 2009 for Incandescent Reflector Lamps and General
Service Fluorescent Lamps. www.bulbrite.com/EISA
: ENERGY STAR is a joint program of the U.S.
Environmental Protection Agency and the U.S. Department of Energy
promoting money savings and the protection of the environment through
the use of energy efficient products and practices. www.energystar.gov
Energy Policy Act (EPAct)
: Energy legislation passed by Congress in 1992 and
updated again in 2005, mandating labeling and minimum energy efficiency
requirements for many commonly used incandescent and fluorescent lamps.
Please note, the Energy Independence and Security Act of 2007 (EISA
2007) and Executive Order (E.O.) 13423 have been issued subsequent to
the passage of EPAct 2005. See Energy Independence and Security Act
Federal Communications Commission (FCC)
: The U. S. Federal agency that regulates emissions in
the radio frequency portion of the electromagnetic spectrum. Part 18 of
the FCC rules specifies electromagnetic interference (EMI) from
lighting devices operating at frequencies greater than 9 kilohertz
(kHz). Typical electronicallyballasted compact fluorescent lamps operate
in the 24 - 100 kHz frequency range.
: The angular dimension of the cone of light from
reflectorized lamps (such as R and PAR types) encompassing the central
part of the beam out to the angle where the intensity is 10% of maximum.
See Beam Angle.
: Wire used in incandescent lamps, usually made of
tungsten and often coiled, that emits light when heated by an electrical
: The unit of measure for the density of light on a
surface. One footcandle is equal to one lumen per square foot (lm/ft2).
One footcandle = 10.674 lux.
: Glare is an interference with visual perception
caused by an uncomfortably bright light source or reflection within
one’s field of view; a form of visual noise.
: A group of inert gases, particularly Bromine, which
is used to reduce the amount of tungsten that plates the interior wall
of the lamp. At high temperatures, the halogen reacts with the tungsten
to form tungsten bromide freeing tungsten from the wall and redepositing
it onto the filament.
: A regenerative cycle of tungsten and halogen atoms,
which prevents blackening of the lamp envelope during the life of the
lamp. See Halogen.
: Lamps that operate with higher lumens (brightness) than the standard model.
High Output Fluorescent (HO)
: Fluorescent lamps designed to be used with an 800
milliampere ballast. These lamps are able to operate at low temperatures
(down to 0oF) and still produce high light levels.
: The total density of visible light - from all directions - illuminating, falling on or incident to, a surface; one
square foot equals one footcandle (lm/ft2), while one lumen per square meter equals one lux (lm/m2).
: The measured luminous output of a new light source.
: A type of fluorescent lamp-ballast circuit designed
to start fluorescent lamps as soon as the power is applied. Originally,
instant-start circuits were developed to eliminate separate mechanical
Integrated Circuit (IC)
: IC-based CFLs operate by controlling the voltage and
current by adjusting the output frequency which provides stable
operation of the CFL. Controlling the current produces less stress on
the cathode and the electronic components, which results in long life,
smoother dimming, and less noise.
International Dark Sky Association (IDA
: IDA is the recognized authority on light pollution.
Founded in 1988, IDA is the first organization to call attention to the
hazards of light pollution. www. darksky.org
: The protection of enclosures against ingress of dirt
or against the ingress of water is defined in IEC529 (BSEN60529:1991).
first digit in the rating is the protection against contact and foreign
bodies. The second digit in the rating is the water protection factor.
IP65 indicates a lamp is totally protected against dust and protected
against low pressure jets if water from all directions - limited ingress
: The Kelvin unit is the basis of all temperature
measurement. In lighting, Kelvin is the unit of measure for color
temperature used to indicate the overall color of the light produced
from a source. See correlated color temperature.
: The measure of electrical power equal to 1000 watts.
Kilowatt Hour (kWh)
: The measure of electrical energy from which electricity billing is determined. For example, at the rate of $0.11
kWh, a 100 watt lamp operating for 1000 hours will cost $11.00 (100 x 1000/1000 = 100 kWh x .11 = $11.00)
: A noble gas used in lamps, typically Krypton lamps offer brighter, whiter light than standard incandescent.
: The lighting industry term for a complete light source package, typically referred to by consumers as a "bulb".
Light Center Length (LCL)
: The distance between the center of the filament, or arc tube, and a reference plane - usually the bottom of the
: Radiant energy that stimulates the sense of sight.
The "visible" part of the electromagnetic spectrum from 380-770 nm.
Light is the energy which allows us to see.
: Light that is directed to areas where it is not
needed, and thereby interferes with some visual act. Light pollution
directed or reflected into the sky creates a "dome" of wasted light and
makes it difficult to see stars above cities.
Light Trespass (Spill Light)
: Light that is not aimed properly or shielded
effectively can spill out at into areas that don't want it: it can be
directed towards drivers, pedestrians or neighbors. It is distracting
and can be disabling.
: See voltage.
: A measure of luminous flux or quantity of light emitted by a source.
: The gradual decline in light output from a light source over time due to filament deterioration and bulb
: A measurement of how a lamp maintains its light output over time.
Lumens Per Watt (LPW)
: A measure of the efficacy (efficiency) of a light source. The number is achieved by dividing lumens produced by
: A complete lighting unit consisting of a lamp (or
lamps), ballast (or ballasts) as required to distribute the light,
position and protect the lamps and connect them to the power supply. A
luminaire is often referred to as a fixture.
: A photometric measure of "brightness" of a surface as seen by the observer, measured in candelas per square meter.
: The light output (lumens) of a light source divided
by the total power input (watts) to that source. It is expressed in
lumens per watt.
: A unit of illuminance or light falling onto a surface. One lux is equal to one lumen per square meter. Ten lux is
Lighting Facts Label
: The Federal Trade Commission (FTC) mandated a new
lighting facts label which will be included on all bulbs intended for
general service purposes. Packaging for standard base LEDs, CFLs and
your household incandescents will show this new two part label over the
next few months leading up to the effective date for this new ruling of
January 1st, 2012. www.bulbrite. com/lightingfacts
Maximum Overall Length (M.O.L.)
: The end-to-end measurement of a lamp, expressed in inches or millimeters.
: The measured luminous output of a light source at: 40% of lamp life for fluorescent and metal halide lamps and 50%
of lamp life for mercury, high-pressure sodium and incandescent lamps.
Maximum of Diameter (M.O.D.)
: The measurement of a lamp’s diameter, expressed in inches or millimeters.
: Metallic chemical element, chemical symbol Hg,
atomic number 80. Mercury is the only elemental metal that is liquid at
ordinary temperatures, with a freezing point of -38 ºF (-39 ºC) and a
boiling point of 674 ºF (356.9 ºC). It is used in Compact Fluorescent,
Fluorescent and HID lamps.
: Light sources that utilize neodymium glass or coating (composed of rare earth elements) to simulate true daylight.
This special glass or coating filters out the yellow light produced by standard incandescent lamps.
: A unit of wavelength equal to one billionth of a meter.
: A rare earth element used to produce modified
spectrum (full spectrum) incandescent lamps; also known as daylight or
natural light. They use a colored glass shell to filter out the yellow
light produced by standard incandescent lamps.
: A measurement for Fluorescent lamp length based on the length of the lamp plus an allowance for the luminaire's
Open Fixture Rated
: Lamps that are approved for burning in open fixtures
(as opposed to enclosed fixtures which have an acrylic lens or plate
: A PAR lamp, parabolic aluminized reflector, which
may utilize either an incandescent filament, a halogen filament tube or a
HID arc tube, is a precision pressed-glass reflector lamp. PAR lamps
rely on both the internal reflector and prisms in the lens for control
the light beam. PAR lamps are also available using LED technology in
which the lens is used to control the beam.
: An inorganic chemical compound processed into a
powder and deposited on the inner glass surface of fluorescent tubes,
CFL's, LED's and some mercury and metal-halide lamp bulbs. Phosphors are
designed to absorb short wavelength ultraviolet radiation and to
transform and emit it as visible light.
: The measurement of light and related quantities.
Power Factor (PF)
: Measurement of the relationship between the AC
source voltage and current. Power factors can range from 0 to 1.0, with
1.0 being ideal. Power factor is sometimes expressed as a percent.
Incandescent lamps have power factors close to 1.0 because they are
simple "resistive" loads. The power factor of a fluorescent and HID lamp
system is determined by the ballast used. "High" power factor usually
means a rating of 0.9 or greater.
: A fluorescent lamp in which the filament must be
heated by use of a starter before the arc is created. These lamps are
typically operated with electromagnetic ballasts.
Programmed Rapid Start
: A fluorescent lamp-ballast circuit that uses a
custom integrated circuit (IC), which monitors lamp and ballast
conditions to ensure optimal system lighting performance. PS ballasts
heat the lamp cathodes to 700oC prior to lamp ignition. This puts the
least amount of stress on the lamp electrodes, resulting in maximum lamp
life regardless of the number of lamp starts. Programmed-start ballasts
are typically wired in series.
: A fluorescent lamp-ballast circuit that is designed with an ignitor to ignite the arc tube. Due to this, bulbs
have no need for
the starter electrode. Pulse start lamps are typically more efficient than standard counterparts.
: A fluorescent lamp-ballast circuit which utilized
continuous cathode heating, while the system is energized, to start
and maintain lamp light output at efficient levels. Rapid start ballasts
may be either electromagnetic, electronic or of hybrid designs.
Full-range fluorescent lamp dimming is only possible with rapid start
Rated Lamp Life
: The length of time of a statistically large sample between first use and the point when 50% of lamps died (no
: RoHS, a European directive, stands for the Restriction on hazardous Substances. RoHS is a regulation for the
the use of certain hazardous substances in electrical and electronic equipment.
: A discharge lamp with an integral ballasting device
allowing the lamp to be directly connected to a socket providing line
Spectral Power Distribution (SPD)
: A graph of the radiant power emitted by a light
source as a function of wavelength. SPDs provide a visual profile or
"finger print" of the color characteristics of the source throughout the
visible part of the spectrum.
: An electronic module or device used to assist in starting a discharge lamp, typically by providing a high-voltage
Starting Temperature (Minimum)
: The minimum ambient temperature at which the lamp will start reliably.
: Lighting designed for a specific visible operation (task) which requires higher light levels; requirements vary
to the proximity to that task and the level of detail involved.
Total Harmonic Distortion (THD)
: A measure of the distortion of the input current on
alternating current (AC) power systems caused by higher order harmonics
of the fundamental frequency (60Hz in North America). THD is expressed
in percent and may refer to individual electrical loads (such as
ballast) or a total electrical circuit or system in a building. ANSI
C82.77 recommends THD not exceed 32% for individual commercial
electronic ballasts, although
some electrical utilities may require lower THDs on some systems.
Excessive THDs on electrical systems can cause efficiency losses as well
as overheating and deterioration of system components.
Toxicity Characteristic Leaching Procedure (TCLP)
: The Toxicity Characteristic Leaching Procedure
(TCLP) test, specified in the Resource Conservation and Recovery Act
(RCRA) of 1990, is used to characterize fluorescent lamp waste as
hazardous or nonhazardous for the purpose of disposal. The TCLP test
measures the ability of the mercury and/or lead in a lamp to leach from a
landfill into groundwater.
: An electrical device by which the alternating current of one voltage is changed (stepped up or down) to another
: Fluorescent lamps that utilize red, green, and blue
phosphor compounds that glow to produce light similar in color rendering
to regular illumination.
: A hard, brittle, corrosion-resistant, gray to white
metallic element extracted from wolframite, scheelite, and other
having the highest melting point and lowest vapor pressure of any metal.
Tungsten and its alloys are used in high-temperature structural
materials; notably lamp filaments.
: An international service group, TUV Rheinland
documents the safety and quality of new and existing products, systems
and services. www.tuv.com
Ultraviolet (UV) Radiation
: Radiant energy in the range of about 100-380
nanometers (nm). For practical applications, the UV band is broken down
further as follows:
- Ozone-producing - 180-220 nm
- Bactericidal (germicidal) - 220-300
- Erythemal (skin reddening) - 280-320
- "Black" light - 320-400
The International Commission on Illumination (CIE)
defines the UV band as UV-A (315-400 nm); UV-B (280-315 nm) and UV-C
Underwriter’s Laboratory (UL)
: A private organization which tests and lists
electrical (and other) equipment for electrical and fire safety
according to recognized UL and other standards. A UL listing is not an
indication of overall performance. Lamps are not UL listed except for
compact fluorescent and LED lamp assemblies - those with screw bases and
: A measurement of the electromotive force in an electrical circuit or device expressed in volts. Line voltage in
the USA is 120V.
: A unit of electrical power. Lamps are rated in watts to indicate the rate at which they consume energy.
: A noble gas used in lamps, typically Xenon lamps offer brighter, whiter light than standard incandescent.
Glossary of LED Terminology
Average Rated Life
: An average rating, in hours, indicating when
a percentage of a large group of lamps have failed, when operated at
nominal lamp voltage and current. The life of an LED is defined as the
operating time in hours for the lamp to reach L70 which designates 70%
lumen maintenance (or 30% reduction in initial light output). Every lamp
type has a unique mortality curve that depicts its average rated life.
: The separation of LEDs according to color temperature
subsequent to a production run for full manufactured, distribution in
terms of color, lumen output and forward voltage. This allows luminaire
manufacturers to select only those LEDs that meet their acceptable
performance ranges and also maintain consistency in production.
Center Beam Candlepower (CBCP)
: The luminous intensity at the
center of the beam of a reflector lamp. Measured in candelas.
: A two-terminal semiconductor device having a p-n (positivenegative)
junction which allows energy travel in one direction.
: A self-contained power supply that has outputs which match the
electrical characteristics of the lamp. It is similar to a ballast and is used
to power illumination sources.
Federal Communications Commission (FCC)
: The U.S. Federal
agency that regulates emissions in the radio frequency portion of
the electromagnetic spectrum. Part 18 of the FCC rules specifies
electromagnetic interference (EMI) from lighting devices operating at
frequencies greater than 9 kilohertz (kHz). Typical electronically-ballasted
compact fluorescent lamps operate in the 24 - 100 kHz frequency range.
: A heat sink is an environment or object that absorbs and
dissipates heat from another object. The design of an LED retrofit lamp's
heat sink is an integral factor in the overall performance of the lamp.
High Power LED
: LED chips can be assembled in two primary methods
for integration in an LED retrofit lamp: SMD (Surface Mount Device) and
COB (Chip on Board).
- SMD – SMD LEDs are enclosed by a housing and the
encased LED is soldered onto the printed circuit board
(PCB). This method of assembly does not have optimal
- COB – COB LEDs are neither encased nor connected.
The LED chips are placed directly onto the PCB through
wire bonding and connected to the contact surface
of the PCB. The benefits of COB technology include
longer life, better performance as well as higher light
output due to better heat conduction in this assembly
: An IES approved method describing procedures and precautions
in performing reproducible measurements of LEDs including total flux,
electrical power, efficacy (lpw) and chromaticity. This is applicable to LED
products incorporating control electronics and heat sinks (LED luminaires
and integrated LED sources).
: An IES approved method for measuring lumen depreciation of
solid-state (LED) light sources, array and modules. This does not apply to
luminaires and does not define or provide methods for estimation of life.
Power Factor (PF)
: Measurement of the relationship between the
AC source voltage and current. Power factors can range from 0 to 1.0,
with 1.0 being ideal. Power factor is sometimes expressed as a percent.
"High" power factor usually means a rating of 0.9 or greater.
: IESNA TM-21-11 provides the method for determining when the
"useful lifetime" of an LED is reached, a point when the light emitted from
an LED depreciates to a level where it is no longer considered adequate
for a specific application through the use of extrapolated data from LM80
testing. Lumen maintenance of LED products and LED packages can
vary by manufacturer. TM-21 ensures consistent lumen maintenance
extrapolation methods for all LED manufacturers. TM-21 extrapolations
are 'best-case' system lifetime estimates, and assume that no other
failure mechanisms influence the life of the LED luminaire.
Total Harmonic Distortion (THD)
: A measure of the distortion of the
input current on alternating current (AC) power systems caused by higher
order harmonics of the fundamental frequency (60Hz in North America).
THD is expressed in percent and may refer to individual electrical loads
(such as ballast) or a total electrical circuit or system in a building. ANSI
C82.77 recommends THD not exceed 32% for individual commercial
: An electrical device by which the alternating current
of one voltage is changed (stepped up or down) to another voltage.
Magnetic transformers use a core and coil assembly transformer to
start and operate the lamp. Electronic transformers operate lamps at
frequencies above 20,000Hz through the use of electronic circuitry.