We hear more and more
about it every day, we want to update our existing lighting technology to LED
but how do we know what we need to look for? Whether you are new to the
lighting retrofit business or a seasoned expert, picking the right LED fixture,
lamp or kit for your space can be challenging. There are so many choices: some
good, some bad and some ugly. How do you choose? This blog post will attempt to
enlighten you more about LED technology, educate you about the benchmarks for
LED efficacy, and explain the importance of evaluating every aspect of a LED
What Are Lumens?
Just as Watts measure the amount of energy in
a light, lumens measure how bright it shines. The term “lumen” actually means
“light,” so that’s an easy way to remember exactly what it is. It’s also
important to realize that Lumens in LED lights are the way to choose LED
lights, not watts. This way of measurement is much more reliable than watts.
In 2011, the US Federal Trade Commission made
it a requirement to measure LED lights by lumens because they deemed it more
important to dictate how bright the bulb was, rather than power output.
Overall, the importance of lumens in LED lights is made clear when it becomes
easier for you to determine minimum requirements for outdoor lighting and other
How to Find the Lumen Output of Your
Existing or New Lighting
The only way to make sure that you will get
the correct amount of light for the area that you intend to light is through a
professional lighting layout. A lighting layout will define the lumen output of
your old fixtures and help to analyze new possibilities that give you the
maximum amount of light while also saving money on your electric bill. XtraLight
provides our clients with a FREE lighting layout and design.
With LED Lighting there is a lot to take into
consideration. One of the biggest arguments is light wattage versus the lumens
and determining brightness. The old way of looking at how bright a light will
be is to look at the wattage, and with incandescent lamps, the higher the
wattage the lamp is, the brighter it is. Now we need to focus on the lumens of
the lamp to determine the brightness of the lamp, especially when it comes to
are all familiar with incandescent lamps and how they are measured in watts (e.g.
40w, 60w and 75w). With LED lighting you may assume the higher the wattage, the
brighter the lamp. However, this is not what you should think about as you
choose LED replacements. Watts and lumens are measured in different ways and
are very different. A watt is a unit of electrical energy –
input. A lumen is a measure of light intensity – output. A light bulb uses watts
to make lumens. As there are so many different types of LED chips with different
lumen outputs, you cannot assume that, for example, all 4w LED lights offer the
same lumen output. There are different types of LED chips: High Power LED, Dip
LED, Lamp LED, SMD, Flux LED and COB LED.
With LED lighting being more
directional, the lumen output to achieve the same brightness will be lower for
LEDs than traditional lighting because a large percentage of the lumen output
is wasted with older technologies.
The energy efficiency of LED products
is typically characterized using efficacy (ratio of power input to light output)
or technically lumens divided by watts. Sounds pretty simple right? There are
some important nuances we need to be aware of. LED products are made up of
packages with their own efficacy.
Baseline – package level efficacy have
many variables that may not be noticeable to specifiers and consumers:
Do I get all the information I need
from the Specification Sheet?
The specification sheet will show in
most cases what the watts and lumens
are of the fixture package. However,
how the light is distributed? What happens if it’s a flood, spot
or any other optic pattern? For
example, LED lighting is far more focused than traditional HID lighting. You can take a traditional 400wMH (458w) and
replace it with a new light fixture with far less wattage, lumen depreciation
and better efficacy. 400W HID has wattage of 458W, lumens of 20,130 and
luminaire efficacy of 44 LPW. With LED fixtures the designer can choose where the lumens go by choosing the right optics and directing
them only where needed, eliminating wasted lumens.
Insert XtraLight Viento photos,
show optic patterns and lumens throw of light how that is important say in a
parking lot where areas are not all the same
Lamp and Luminaire Efficacy
Thermal effects, driver losses, and
optical inefficiencies all combine to reduce the efficacy of LED luminaires
compared to the included LED packages. Considered collectively, these loss
mechanisms can result in a decrease in efficacy of greater than 30%. Notably, the
efficacy of complete LED lamps and luminaires is most relevant to building
A major factor in determining the
lumen output of an LED is junction temperature. As temperature increases, the
light-generation process becomes less efficient and fewer lumens are emitted. For this reason, LED luminaires
generally require a thermal management system. However, even in a well-designed product, the junction temperature may rise
significantly above laboratory conditions, which could result in up to a 15%
decrease in efficacy. Always understand the conditions of the space in choosing
the right LED luminaire.
Fluorescent and HID light sources
cannot function without a ballast, which provides a starting voltage and limits
electrical current to the lamp. Similarly, LEDs require a driver, which is comprised of both
a power source and electronic control circuitry. Most drivers convert line
voltage to low voltage and current from AC to DC, and may include supplementary
electronics for dimming and/or color correction. In choosing the correct driver
for the system the LED manufacturer considers many variables, dimming, lumen
output, voltage all important features essential to optimizing the lighting
Regardless of source type, the use of
lenses, reflectors or other optical systems to shape a product’s distribution
ultimately reduces the total amount of emitted
light. For LEDs,
this is another contributing factor in the difference between package efficacy
and lamp luminaire efficacy. However, the magnitude of the effect is difficult
to state given the large diversity of fixtures in the marketplace.
Terms Commonly Used When Referring to Lumens
LPW – Lumens per Watt. The number of lumens produced by a light
source for each watt of electrical power supplied to the light source.
LUMEN DEPRECIATION – The decrease in lumen output of a
light source over time; every lamp type has a unique lumen depreciation curve
(sometimes called a lumen maintenance curve) depicting the pattern of
decreasing light output.
For instance, a 400 watt metal halide
depreciates nearly 70% in the first 3 years vs a comparable LED High bay
fixture which depreciates 30% over 50,000 hours, one of the distinct advantages
of LED lighting.
LUMEN MAINTENANCE – The deterioration in the amount of
light that is emitted from a lamp over time. A lamp with good lumen maintenance
will emit a consistent amount of light over its lifetime, emitting as much as
90% of its original capability at the end of its lifespan.
LUMINAIRE – A complete lighting unit which
contains a lamp/LED board, housing, driver/ ballast, sockets and any other
LUMINAIRE EFFICIENCY – The ratio of lumens emitted by a
luminaire to the total lumens emitted from the light source within the
LUX – A
unit of illuminance equal to 1 lumen per square meter.
MEAN LUMENS – The average lumen output of a lamp
over its rated life. Mean lumen values for fluorescent and HID lamps are
typically measured at 40% of their rated lives.
INITIAL LUMENS – The lumens produced by a lamp after
an initial burn in period (usually 100 hours).
How LED Lighting differs from other
energy-efficient lighting technologies?
LEDs offer the
potential for cutting general lighting energy use nearly in half by 2030,
saving energy dollars and carbon emissions in the process. LEDs have many
unique characteristics – including compact size, long life and ease of maintenance,
resistance to breakage and vibration, good performance in cold temperatures,
lack of infrared or ultraviolet emissions, and instant-on performance, these
are all beneficial in many lighting applications. Additionally, LEDs have the
ability to be dimmed and to provide color control.
Do LEDs Provide High Quality Light?
Key aspects of high-quality light are
the color appearance of the light itself, which is described by its correlated
color temperature (CCT), and how the light affects the color appearance of
objects, which is commonly called color rendition. Color rendition can be
quantified using the color rendering index (CRI), or with one of several other
recently developed metrics. LED light sources have demonstrated that they can
achieve a wide range of color quality, depending on the demands of the lighting
application. However, in order to achieve high levels of color quality, there
are typically cost and efficiency tradeoffs. In general, a minimum CRI of 80 is
recommended for interior lighting, and LED products can readily achieve this
performance. CRIs of 90 or higher indicate excellent color fidelity; LEDs can
also meet this threshold. CRI is far from a perfect metric and is especially
poor at predicting the fidelity of saturated reds, for which the supplemental
value R9 is often used. New metrics, such as the fidelity index (Rf) and the
gamut index (Rg¬), which are described in IES TM-30-15, can provide a more
comprehensive evaluation of color rendering. Learn more about TM-30-15 and LED
How Long Do LEDs Last?
LED luminaire useful life is often
described by the number of operating hours until the LED luminaire is emitting
70 percent of its initial light output. Good-quality white LED lighting
products are expected to have a useful life of 30,000 to 50,000 hours or even
longer. A typical incandescent lamp lasts about 1,000 hours; a comparable CFL,
8,000 to 10,000 hours; and the best linear fluorescent lamps, more than 30,000
A primary cause of lumen depreciation
is heat generated at the LED junction. Unlike other light sources, LEDs don’t
emit heat as infrared radiation, so it must be removed by conduction or
convection. Thermal management is arguably the most important aspect of
successful LED system design.
Are LEDs Cost-Effective?
Costs of LED lighting products vary
widely. Good-quality LED products may carry a significant cost premium compared
to standard lighting technologies. However, costs are declining rapidly. LED
package prices declined to approximately $1/klm by 2016, resulting in
dramatically reduced LED lamp and luminaire prices. In general, LED lighting
products are still more expensive than their conventional counterparts, but
when the costs of energy and maintenance are included in the total cost of
ownership, LED-based products can have a distinct advantage.
The efficacy of LED products has
steadily improved since their introduction as a source for general
illumination. This trend is expected to continue, thanks to new materials,
better manufacturing processes, and new configurations.
Currently, the efficacy of LED
packages compares favorably to conventional light sources. Many integrated LED
lamps and luminaires have efficacies that are comparable to their traditional
counterparts, but the viability in LED products is greater than the mature
technologies and the LED products are changing rapidly.
Importantly, you must look at other
characteristics when choosing LED technology: color quality, luminous
intensity, distribution and the ability to be dimmable. Although high efficacy
is an important attribute for energy savings, it is unperceivable to the users
of the space. By just choosing a fixture based on wattage and lumens alone and
not considering where the lumens are being used and/or lost, the project may
not produce the financial success you strived for.
LED technology is still rapidly
changing. When considering an LED upgrade, remember that the ratio of watts and
lumens is very important but also to know where the lumens are going. Are they
wasted? Partner with a trusted manufacture that can perform photometric
testing, can design with the right fixtures, provide precise optical patterns
and recommend the right packages for your space.