The technology known as LED stands for light-emitting diode, and when it's built into bulbs, lamps and other lighting fixtures, it's significantly more efficient than incandescent or fluorescent light. As this chart demonstrates, the cost of LED A-type bulbs — the standard-looking ones you're going to see at the hardware store — has dropped dramatically: 94 percent in seven years.
It's no coincidence that, in turn, A-type bulb installations have increased dramatically. In 2008, about 400,000 LED bulbs were installed in the United States. In 2014, that number was 77 million. At the end of 2015, the Department of Energy estimates there were more than 200 million bulbs installed in nationwide. LED lamps and bulbs consumer up to 85 percent less energy than old-school incandescent bulbs.