Over a span of only a few years in the early to mid-2010s the lighting industry was revolutionized by the arrival on the market of products using light-emitting diodes (LEDs) for general lighting applications. During that period, LED lighting products underwent both a dramatic growth in sales along with a precipitous decline in price. In the United States alone, sales of LED-based standard household light bulbs rose by more than two orders of magnitude, while falling nearly 10-fold in price. This rapid rate of change in both price and production represented an excellent opportunity for tracking the effects of technological learning in real time. Measuring the learning effect directly on manufacturing costs is challenging, owing to a lack of available data on cost, as well as very rapid evolution in product design. Because LED products are sold directly to consumers through online retail channels, it was possible to use web-crawling techniques to track retail prices at high frequency and track the price decline in great detail. A variety of studies using web crawling and other retail tracking approaches pointed consistently to a steady 20%30% annual rate of price decline for household LED light bulbs from 2011 to 2018, in both the United States and elsewhere. Coupling this with a public sales index for the US market, a picture emerges of a technological learning curve characterized by an 18% price decline for each doubling of cumulative sales. Projecting these trends forward implies that substantial price declines are still to come, with prices expected to drop by more than a factor of four between 2015 and 2030.