The first time I saw an LED was when my Aunt Sheila brought a Texas Instruments LED watch from America in 1977.
More recently, Shuji Nakamura, Isamu Akasaki and Hiroshi Amano won the Nobel Prize for physics in 2014 for their work on blue LEDs, which were essential in the development of the white LEDs now used in lighting.
LED lightbulbs currently have an efficiency of up to 223 lumens per watt. For comparison, incandescent lamps typically put out about 16 lumens per watt (LED bulbs also last about 20 times as long as incandescent, so more savings there).
Apparently, about 10% of global energy production is consumed by lighting, so the potential savings in CO2 emissions are huge.
On a smaller scale, this article in Which? magazine says the average household could save £232 by switching from halogen to LED bulbs.
I’m going to switch all our remaining CFL and incandescent bulbs (There are only a few left) to LED over the coming few months.