LEDs are the most efficient light source
This is best examined by comparing the luminous efficacy of different lighting sources. This is a measure of how efficiently a light source converts electrical energy into visible light. So this figure takes into account wasted heat as well as how "useful" the emitted light is.
Incandescent light bulb 14-17 Lumens/Watt
Halogen 20-24 Lumens/Watt
Compact Fluorescent 46-75 Lumens/Watt
T12 fluorescent with magnetic ballasts 60-65 Lumens/Watt
White LED 80-110 Lumens/Watt
T5/T8 fluorescent with electronic ballasts 70-100 Lumens/Watt
This comparison of the Luminous Efficacy of a number of different light sources shows that LEDs are not much more efficient than energy saving lamps (CFLs). Fluorescent lamps with electronic ballasts are more efficient.
LEDs are good for some application
This is very true. LEDs are very good at localised lighting for example for architectural mood lighting, worktop lighting, corridor lighting where the light level is not required to be very bright and a narrow beam is acceptable. In fact it is this feature of LEDs that lead some to believe that LEDs are super efficient. Because they produce a narrow beam of light compared to CFLs, it appears that they are throwing out more light than the CFLs. However if the CFL was mounted in a good fitting with reflectors to produce a narrower beam, the lighting outputs would be comparable.
LEDs can be controlled very easily
This also is very true. LEDs can be dimmed, switched on and off without any deterioration to the life of the devices. Unlike CFLs which take some time to reach full brightness, LEDs reach their full brightness instantly. This makes LEDs ideal for applications where daylight or occupancy dimming is being utilised.
LED lighting is very reliable
LEDs themselves are very reliable and it is not unusual to see operating life of around 100,000 hours quoted for them. However they require electronics to drive them, and this can reduce the useful life. If many LEDs are used then the solder joints can be another source of failure. Additionally high powers LEDs require good thermal management to conduct the heat away. If this is not done properly the failure rate can be high.
When assessing the life of LED lighting it is very important to take all the above factors into account and look for a "system life".
One day ALL lighting will use LEDs
Certainly LEDs will find wider use as more powerful ones emerge. Already many traffic lights and car rear lights are designed with LEDs as these need to be quite directional in a relatively narrow beam.
However there are some applications where LEDs will struggle to compete with other forms of lighting and will fall short of the lighting levels required. For example in retail, office, warehouse and production areas where bright lighting levels are required.
