One of the fastest developing lighting technologies today is the light-emitting diode (or LED). A type of solid-state lighting, LEDs use a semiconductor to convert electricity into light, are often small in area (less than 1 square millimeter) and emit light in a specific direction, reducing the need for reflectors and diffusers that can trap light.

They are also the most efficient lights on the market. Also called luminous efficacy, a light bulb’s efficacy is a measure of emitted light (lumens) divided by power it draws (watts). A bulb that is 100 percent efficient at converting energy into light would have an efficacy of 683 lm/W. To put this in context, a 60 to 100-watt incandescent bulb has an efficacy of 15 lm/W, an equivalent CFL has an efficacy of 50-70 lm/W, and current LED-based replacement bulbs on the market range from 90-140 lm/W.