High-efficacy LEDs are already delivering significant electricity savings worldwide—it also helps that they can provide light for three hours a day for about 20 years, and if you forget to switch them off you will hardly notice on your next electricity bill. But, much like all other sources of artificial light, they still cannot match natural light’s spectrum. Incandescent lights gave out too little blue light, and fluorescent lights had hardly any red; LEDs have too little intensity in the red part of the spectrum and too much in the blue part. They don’t quite please the eye.
