Announcements planned for 2010 show LED efficacy well exceeds that of fluorescent technology.  As you read here, keep in mind that LED justification and ROI (return on investment) are different between indoor and outdoor lighting.  When you have prices and specifications for LED products with comparable and adequate lighting capability, use this Payback Calculator to determine if it's right for your application.

The LED manufacturer rates lumen output at a specific junction temperature, typically 25°C, and some luminaire marketing will use that lumen figure to promote a new LED light.  Few LEDs perform in the real world as they did in laboratory tests.  LED marketing has become clever and caused the lighting industry to think in terms like "wall plug efficiency."    (Note that Energy Star calls this "Luminaire Efficacy")

Selling LED lighting isn't so easy.  Because the LED is more expensive, you may be told that LEDs make better light, e.g. scotopic advantage.  Be skeptical of proposals offering less foot candles or reduced fixture count.  Remember - If you were willing to reduce your lighting levels, you would save energy without spending money on LED fixtures.  By definition, "lighting" is to illuminate, which is quite different from accent lights and display devices; your sales person may need better training.  See Meeting the Standards later in this article.

Here we discuss a few hopeful ideas or rumors, and some of the reality to support or dispel them. 
Let's get started.  If you are new to LED technology, see "About LEDs" for a basic overview. 
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That seems like a practical statement since LED traffic signals saved over 80 percent when they came on the scene.  But beware.

LED traffic signals saved energy because the signals are monochromatic (single color).  The extra color spectrum generated in incandescent bulbs was absorbed in a filter (colored lens) and LEDs naturally emit only a single color so there's no extra light generated to throw away. 

The issue of saving energy with LEDs comes down to producing only what the task requires, AND using all the light that is produced.  Competing technologies may produce higher lumens, but it's not easy getting all that light where it's needed, and usually any extra light is just masked.

A typical bulb type luminaire may be only 60% effective, or in other words, a lot of the light it produces doesn't go to the intended target (it becomes light pollution or it can't get out of the luminaire).  And, the higher efficacy HID bulbs require a ballast to start the arc and regulate the gas ionization.  The ballast may consume more than 20% of the electrical energy going into the luminaire.

   That's  0.6 × 0.8 = 0.48
       or  Metal Halide = 80 lumens/watt × 0.48 = 38   delivered lumens per watt.

In contrast, the LED luminaire may be 90% effective with a power supply that's 90% efficient. 
   That's  0.9 × 0.9 = 0.81
          or  LEDs = 70 actual lumens/watt × 0.81 = 57   delivered lumens per watt.
Myth Busted
The LED will not easily pay for itself with energy savings alone when equal illumination is required.
Use a Payback Calculator to be sure.

High lumens are not always required for certain tasks, just because older luminaires were so inefficient.  Where have all those lumens been going, and at what cost to the consumer? 
Is this deceptive?  You bet it is.  This I call the "Lumen Legacy." 
See this breakdown on Sodium Lighting effectiveness.

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	: ef·fi·ca·cy Pronunciation: 'e-fi-k&-sE Function:  noun  Inflected Form(s):  plural -cies  : the power to produce an effect

"Efficiency" does not relate a measure of input energy to a unit of light output.  Luminous Efficacy is the appropriate term for comparing a light effect from an electrical input, and is commonly used by lighting specialists and LED Engineers worldwide.  Efficiency would be used for example, to compare power in to power out of a power supply, or, compare the light produced by a bulb inside a fixture to the light emitted from that fixture, etc.  "Light" refers only to the visible portion of the spectrum, and not to other emissions. 

Lighting Type	Efficacy (lumens/watt)	Lifetime (hours)	Color Rendition Index (CRI)	Color Temperature (K)	Indoor/ Outdoor
Mercury vapor	25–60	16,000–24,000	50 (poor to fair)	3200–7000 (warm to cold)	Out
Metal halide	70–115	5,000–20,000	70 (fair)	3700 (neutral*)	In/Out
High Pressure Sodium	50–140	16,000–24,000	25 (poor)	2100 (warm)	Out
Fluorescent	57–70	10,000–15,000	79 (fair)	2700–6000 (warm to cold)	In/Out

LED chip manufacturers are boasting of 100+ lumens per watt (at 25°C  T_J  of course). 
Outside the laboratory, in the real world, LEDs rarely deliver over 70 lumens per watt. 

The barrier to keep an eye on in the LED illumination business is not the efficiency, it's the LED's high cost per lumen.  HID bulbs can jump in increments of ten thousand lumens for mere dollars, whereas LEDs cannot.
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Several LED luminaire suppliers are trying to use a Scotopic Advantage  when promoting less lumens to do an equivalent lighting job.  There will be lots more to come on this subject, so check back for updates.  In the meantime, here is a LRLL white paper that shines some light on the OUTDOOR Scotopic issue. 

One sales pitch for indoor lighting promotes LEDs to replace Metal Halide and Fluorescent for factory assembly work areas, claiming less footcandles are acceptable due to that Scotopic Advantage    This couldn't be more misleading since detailed assembly work requires good spectral coverage AND at least 30-50 foot-candles. 

This Scotopic Advantage  is possible only when new lighting improves spectral content AND luminance is below 3cd/m²  (approx. 6 foot-candles).  You might never find that condition for indoor task environments.  Visual work requiring direct focus and color rendition relies upon the cones, which allows NO Scotopic Advantage. 

Another case of buyer beware, and a potential black eye for LED sales people. 
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Entrepreneurs may need to re-write a few laws of thermodynamics when showing screw-in LED light bulb replacements.  These inventions need more thought to live up to claims.

Will the consumer settle for less light because it's a novel gadget?  Reducing their lighting requirements will itself save energy, but is that what they intended?  This leaves the market open for a rude awakening - buyer beware?

LEDs produce more light per watt than an incandescent bulb.  But most of the watts they consume is still converted to heat, and if not dissipated, will drastically shorten their life.  Heat doesn't radiate from an LED, so it must be conducted away, usually into an exchanger to free flowing air.  The LED junction must operate below about 85°C. 

A light bulb is fundamentally a heater that just happens to send out a little visible light.  Yes, a heater, and the socket it's screwed into is designed to protect the base and wiring from all that heat.  In other words, the socket is a very poor thermal path for cooling that screw-in LED light bulb.  Something must cool the LED, and cooling will not happen through the socket.

Each watt of LED power needs about 6 square inches of surface area in free air for cooling. 
That 3" post-it-note on your desk is 9 square inches.  Roll it up, fold it & shape it to get an idea of the size neded to dissipate about 1.5 watts. 

If the LED has twice the efficacy of incandescent, then lumen for lumen, a 60-watt light bulb replacement must dissipate 30-watts of heat.  That's about 180 square inches of surface metal attached to that screw-in LED device.

To get the lumens and keep the life, you gotta cool that thing.  Of course an alternative is forced air with a fan.
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On the surface that statement is partially true.  We don't get a monthly bill for using the Sun's energy, and the process of converting the Sun to electricity produces no harmful side effects.  However, lighting is needed at night when the Sun is not around, so our night lighting is powered by energy stored during the day in batteries.  Batteries contain materials that aren't land-fill friendly, and they must be replaced every few years, so costs are quite high.  Photo-voltaic cells are the key to harnessing the Sun's rays, and those cells are not cheap.  The solar panels may cost 2 or 3 times that of the light they power, and the amortization may be 30 or more years.

Solar powered nighttime lighting can be justified only when there is no electrical service, or, when complete independence from the utility company is essential.  Solar power isn't likely to win if the competing power source is hydroelectric.
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Technology has come into the equation, and with that comes many ways to measure performance and even ROI.  Electronic controls are now involved that can inform the owner of pending failure or lumen depreciation, they can allow remote control of your luminaire.  Can you imagine a communications protocol between streetlights and your central office?  It's here.  Now you need interchangeability, and NEMA can drive manufacturer functional compatibility.

Spreadsheet generated Photometric files are here too.  NEMA can draft appropriate performance Standards, and possibly find ways to police deceptive practices.  We used to expect the Photometric file came from an independent lab, but until there are NEMA Type numbers for Luminaires, you should insist on Certified Independent IES Files and Test Lab Report before committing poles and luminaires.

We can hope that NEMA will raise Manufacturer Standards and Ethics.     Leave your comments here.
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Claims like this will make skeptics of us all. 
A particular IESNA (Illuminating Engineering Society of North America) "Standard" must be identified by number, e.g. RP-1, RP-8, RP-20, etc. 

IES LM-63-95 is the IESNA Standard File Format for Electronic Transfer of Photometric Data.  This is a photometric file; a tabular format representing typically a 180° x 360° plot of candela measurement. 

An LM-63 photometric file along with layout software, can determine the quantity, location and spacing for luminaires to provide lighting levels and uniformity based on your selection.  Your luminaire manufacturer must provide this photometric file for the luminaire. 

Type Classification
The IES roadway classification system is based on the position of a half-maximum candela line plot.  Any luminaire, indoor or outdoor, can be classified regardless of style, technology or lumen output. 
  
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LEDs have a reputation for long life, but they are also easily abused.  Light Emitting Diodes are more fragile than some designers are aware, but electrical or thermal deficiencies in their fixture design will not often cause a sudden failure.  Too much current or too much heat, for example, could result in a 50,000 hour part lasting only 10,000 hours. 

High quality, high output monochromatic LEDs can provide 70% of their original lumen output at 100,000 hours IF they are not abused.  Note that Monochromatic is stipulated because the Phosphor in PC (Phosphor Converted) white LEDs can degrade faster than the LED junction.  This can be caused from thermal overload, excessive ultra-violet exposure or moisture.  Most manufacturers have overcome these problems, now the integrator must adhere to good science.  See the previous section here Screw-In LEDs Replace Bulbs.

As an example, I have tested this Journée Lotus product, and found the heat sink section to exceed 65°C with a room ambient of only 24°C.  A rise this high will surely limit the LED life to far less than the manufacturer's claim of 40,000 hours.  The phosphor output shifts through several colors while the assembly is stabilizing, which is a good sign the phosphor is not very happy.  But as an office or desk lamp, if you don't leave it on all night, how many years is 10,000 hours, really?  So you need to be careful not to burn yourself, because it will leave a welt.     Time will tell.
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Correlated Color Temperature Chart

Color Rendering Index  (CRI) indicates how well a test source renders eight standard colors of intermediate saturation, when compared to a reference lamp of the same color temperature.  Lab measured CRI is a comparison against a spectrally continuous red-weighted reference.  Field conducted CRI tests are subjective with Human observers when luminance levels are below 3 cd/m2. 

The industry is discovering that CRI is not the best metric for comparing LED light sources, especially at Mesopic levels.  Originally developed in 1964, this index is based on outdated color models and assumes illumination sources with broad spectral distributions, whereas LEDs are narrow-band sources.  And, nighttime lighting requirements fall primarily in the Mesopic range where our color sensitivity shifts with luminance, and there is no defined index.  Several standards bodies are addressing this deficiency, and in the interim, Color Temperature may be the most suitable tool for comparison because it is independent of observer subjectivity.  Click for more...

Correlated Color Temperature (CCT) defines a color as the temperature in degrees Kelvin that a "black body" source must reach in order to produce that same color.  CCT describes the dominant color without regard to Human visual response or the source technology and is more appropriate for comparison of visual effectiveness at lower light levels and among different technologies. 

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Which measurement shall I use:  Candela or Lumens?

The user community, contractors, agencies and municipalities, have established lighting criteria so they can maintain a quality of illuminance through time.  Specifying a lighting fixture by lumens is merely requiring a power consumption and not a lighting criteria. 

Indoors:  Dimensions of an area illuminated does define minimum delivered lumens, but lightmeters measure footcandles or lux. 
              Calculate the minumum delivered lumens  required:  (square ft.  ×  foot-candles)  + 10%
NOTE - this is an approximation that will depend on fixture placement, mounting height and angles, and when estimating, add at least 10%.  It may help you get into the ball park.

Outdoors:  Properly managed LEDs in a suitable luminaire have been field-measured as placing 3-times more foot-candles on the ground per watt than other technologies, partly because they can be directed where most suitable, and partly because they produce light only where needed. 

Be careful of the Lumen Legacy.  Select fixtures based on application footcandles or lux rather than lumens.
Now we have LEED certification to ensure Green.
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The popularity of LED Lighting brings a lot of wannabe experts to the scene.  Even with poorly designed products lacking quality control in production, LED products may survive the warranty period and never give the R.O.I. you paid for. 

Your LED product should be built to at least   ISO 9001:2008 certification.
Is the manufacturer listed as an Energy Star Partner?

Begin with a Google or Yahoo Search.  
Type in the company name or product (within quotes if more than one word) followed with keywords,
  e.g. failure, fault, recall, etc.   

Next search financial records and duration in business, then see if their state of filing records are up to date.  Today, it's a red flag if LED Lighting companies haven't shown reasonable growth (at least 25%) within the first two years. 

There are several sites on the Internet that make this research an instant reality.
        Manta is a free business record service, you register to use.
        Hoovers a free trial D&B Business Search Service
        Free Public Records Finder
        Experian Business Reports for a fee

Next, check their status in the State where they filed for incorporation.  You can search for any state with SOS (Secretary of State) Business Entity Search. 
      Here are a few links for example.
When you find the company, hope to see "Active" rather than "Default" or especially "Revoked" or even "Permanently Revoked".
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