To guarantee the best performance from an LED efficient heat dissipation is essential. LED's only convert about 25% of the electricity they consume into visible light. The rest of the power is converted into heat energy which must conducted away from the LED and dissipated into the atmosphere. This unwanted heat if not managed correctly will destroy the LED resulting in greatly reduced lifespans as well as lower efficiency and reliability.

There are 2 main techniques used to remove heat away from LED's. Active and passive cooling.

Passive cooling is the most common using finned heat-sinks made from cast or extruded metal. These types do not suffer from performance degredation over time and do not make any noise.

Active cooling types are less common. They include fan and liquid cooling and are capable of dissipating larger amounts of heat, however they generally produce noise, are more expensive and suffer from performance degradation over time.

An optimal thermal management system is an primary requirement in LED solid-state lighting (SSL) lamps and luminaires in order to deliver long lifespans and consistent color and lumen outputs. Realizing such an optimal design starts in the engineering lab with accurate models and design simulations, includes correct selection of thermal products such as heat-sinks, and continues through to a robust manufacturing plan. 

Low power consumption

  

Dimmable

LED is dimmable as long as the LED lamp or fittings driver circuit is of a dimmable type (refer to Dimming LED). Although halogen & incandescent are easily dimmable, fluorescent, mercury vapour, matal halide & high pressure sodium are not.

  

Higher efficiency

LED wastes far less energy in the form of heat than traditional lighting types. LED= 50lm/W, incandescent= 15lm/w. Despite this LED is only about 10% efficient. Haitz law predicts that the efficiency of LED will double once every 3yrs & to date this has proved to be true.

 

No UV or IR spectrum emitted

Because LED doesnt emit light in the UV or IR spectrum it attract far less insects. These wavelengths of light are also wasted energy as they can't be seen by the human eye.

High CRI

CRI is the ability of the light to accurately represent the object being illuminated. LED generally has high a CRI (>90CRI). Cheap ebay LED usually doesn't. Halogen & incandescent have high CRI (>90CRI) but fluorescent lighting CRI is very low (>70CRI).

Reduced maintenance costs

Everytime a light is relamped it will cost between $5 & $10 in labour plus the cost of the new lamp. A halogen or incandescent lamp will be relamped approximately 25X over the lifespan of just one LED lamp! Also because LED are solid state & have low operating temperatures they are far less prone to decay or breakage. The failure rate of LED is also very low & is ±1% within its expected lifespan.

 

Instant start time & ability to cycle on/off

The ability of LED to switch instantly makes it perfect for use as security lighting with a sensor. Unlike Fluoro/MV/HPS/ MH which require a warm up time in the range of 5-10 minutes.

 

Shock & vibration resistant. (solid state) 

LED are solid state devices which means they are very robust. As they dont have a filament like halogen or incandescent they can handle a drop. 

Low operating temperature

The operating temperature of LED is between 20º-40º, this is because LED is very heat sensitive. A heatsink is used to dissipate the heat created at the LED's junction which is the place where the light is produced. If they are allowed to overheat it will greatly reduce their lifespan but this also makes them a very low fire risk.

Any colour in the visual spectrum

LED can be any colour in the visual spectrum. There by adding various compounds to the diode during production a LED can be any colour desired. The other way to achieve this is by colour mixing the 3 primary colours of light. By varying the levels of red, green & blue light in a fixture we can achieve any colour in the spectrum. 

   

Control gear/power supplies draw & therefore cost less

Regulated DC power supplies are ±98% efficient. Compare this to the old heavy wire wound downlight transformers or fluorescent ballasts which are <90% efficient & will over time add up to the cost of a LED lamp in wasted energy.

Ability to focus light with a lens

Because LED light is emitted from a single point source it is much easier to focus its beam with a lens. This is a more efficient & more compact way than the alternative which is to use a reflector.

 

Small physical size

LED's are small in size which enables them to fit in places that others can't. A notable example is the LED flexible tape which is replacing fluorescent tubes used in pelmet lighting. Where the fluorescent used to stop shy of corners because of its fixed tube size the flexible tape can be cut every 50mm to get to the corners. It can be used on a curved section unlike the fluorescent & will also be free from the gaps of light seen where the fluorescents butted together thus providing even & consistent light.

 LED -

Higher initial price
Although the initial cost of LED is high, you're investment can be recouped 20X over time in energy savings & reduced maintenance costs. This makes LED the cheapest lighting available.

Effected by temperature
Keep the ambient operating temperature under 50º or lifespan is reduced. Be careful of installing LED in extremes like direct sunlight or surrounding it in thermal insulation where heat cant dissipate. Install a sunset switch if your LED is exposed to direct sunlight, this will ensure the LED is protected during the day when the light isn't required.

Voltage sensitive
LED's are highly sensitive to voltage fluctuations & can blow instantly with overvoltage of even 1 or 2 volts. Always use the correct voltage. Using a regulated power supply for low voltage LED will ensure that the voltage will never exceed the operating voltage 

Colour correction
At around ±2000hrs LED will warm. Although the effect is mostly negligible the cheaper ebay LED can warm by as much as a few 100 kelvin.

Gradual dimming
LED will gradually dim over time as it reaches the end of its life. This happens in the last 10000hrs & is instead of the instant blow that occurs with filament lamps. This can be as positive as it can give you ample time to  prepare for a relamp.
 

Beware of cheap LED
Buyer beware! With LED you really do get what you pay for. Cheaper LED like a lot of the stuff sold on ebay can have all sorts of potential problems. Poor CRI, incorrect colour temperatures are a few of the things to watch out for. Overdriving the LED to boost initial performance can be paid for with greatly reduced lamp life.