LEDs differ in producing light

JG 0512
Interesting Facts on LED Lighting
Advantages of LED Lighting
 Compact size, Long life, Low maintenance, Resistance to breakage/vibration, Instant-on
 Average LED life is 30,000-50,000 hours; fluorescent tube is 10,000-20,000 hrs; compact
fluorescent (CFL) is 8,000-10,000 hrs; incandescent is 1,000 hrs
 They use about half the energy (watts) of a fluorescent tube
 LEDs do not burn out – they get progressively dimmer over time
 Very good dimming and color control
LEDs differ in producing light
 Incandescent/Fluorescent/Sodium/Halide are natural light sources (think the sun)
o They emit white light
 White light is the sum of all colors
o They emit infrared radiation (i.e. produce heat into the air)
 LEDs are not a natural light source
o They are monochromatic (single color)
 Makes them great for traffic lights and other single color applications
o To produce white light, they typically use InGaN base with a phosphor coating
 Although not practical, they can also use Red/Green/Blue LEDs in
combination– remember old “RGB” monitors and rear-projection TVs
o They are cool to the touch as they don’t emit infrared radiation
 They are sensitive to thermal and electrical conditions so thermal
management at the LED junction is very important to longevity
 They must dissipate heat via conduction (touch)/convection (moving air)
 You’ll see heat sinks on the luminaire - large metal fins on the casing
behind the LEDs to provide cooling
 Use a thermal imager to see the location of the heat!!
 LEDs produce directional light
o Natural light sources emit light in all directions
 40%-50% of light can be lost before leaving fixture
o LEDs good for focused downlighting
o Many LEDs are contained in a single bulb housing at various angles to broadcast
light over a larger area
LEDs keep coming down in price with advances in technology
 LED luminaires have an initial cost premium over other light sources
o Investment payback is much closer when maintenance and energy consumption
are factored in with the purchase price
 Costs are declining fast -- dropped 50% in one year (2010) to $18 per kilo-lumen (klm).
By 2015, they are projected to be $2 per klm.
Information is from the Department of Energy (DOE).
LED lighting has the highest efficacy – efficiency of device and fixture in total:
Product Type
Typical Luminous Efficacy (in lm/W)
LED cool white package
LED warm white package
LED A19 lamp (warm white)
LED PAR38 lamp (warm white)
High intensity discharge (high watt)
Lamp and ballast
Linear fluorescent
Lamp and ballast
High intensity discharge (low watt)
Lamp and ballast
Compact fluorescent lamp
Typical LED Efficacy Compared to Conventional Lighting
Technologies in 2010