Energy Saving--The key strength of LED lighting is reduced power consumption. When designed properly, an LED circuit will approach 80% efficiency, which means 80% of the electrical energy is converted to light energy. The remaining 20% is lost as heat energy. Compare that with incandescent bulbs which operate at about 20% efficiency (80% of the electrical energy is lost as heat). In real money terms, if a 100 Watt incandescent bulb is used for 1 year, with an electrical cost of 10 cents/kilowatt hour, $88 will be spent on electricity costs. Of the $88 expense, $70 will have been used to heat the room, not light the room. If an 80% efficient LED system had been used, the electricity cost would be $23 per year - there would be a cost savings of $65 on electricity during the year. Realistically the cost savings would be higher as most incandescent light bulbs blow out within a year and require replacements whereas LED light bulbs can be used easily for a decade without burning out.
Long Lifespan--The life of a high-power white LED is projected to be from 35,000 to 50,000 hours, compared to 750 to 2,000 hours for an incandescent bulb, 8,000 to 10,000 hours for a compact fluorescent and 20,000 to 30,000 hours for a linear fluorescent bulb. LED lifetimes are rated differently than conventional lights, which go out when the filament breaks. Typical lifetime is defined as the average number of hours until light falls to 70 percent of initial brightness, in lumens. LEDs typically just fade gradually.
Eco-Friendly--"Switching 52M US street and high way lights to LED fixture would have saved 20.2 terawatt hours in 2010." and "In 2010 around 0.38 terawatt hours were saved due to the LED replacement. LED replacement can eventually achiece up to 133 TWh hours per year in energy saved nationwide."--US Department of Energy