By one estimate, lighting in the U.S. commands 22% of electricity usage. Shifting to CFL bulbs helps, since they are three times more energy efficient than incandescent bulbs. But because they use mercury, which has dire consequences on wildlife, CFLs are seen as simply a stop-gap measure until the next wave of lighting matures. This next generation technology is LED, or light-emitting diode. Like the name suggests, LEDs aren’t bulbs like we think of them, but a collection of small silicon chips-like instruments that emit a certain color of light. They use so little electricity that when Prince Charles...