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In April 1954, top scientists gathered in Washington, D.C., to hear something new: voice and music broadcast by a solar-powered radio transmitter. Scientists at Bell Labs in New Jersey were demonstrating their invention, the first practical solar cell, which was made of silicon. This breakthrough paved the way for the solar revolution taking place today on rooftops and in massive ground-mounted solar farms around the world.

Solar cells, also called solar photovoltaics or PV, powered U.S. satellites during the 1960s space race with the Soviet Union. But PV technology was still too expensive to be used for much else until the Arab oil embargo of 1973. Amid rising fears about energy security, governments and private firms poured billions of dollars into solar research and development, reaping big gains in efficiency and cost reductions. This led to widespread use of PV in the 1980s for powering telephone relay stations, highway call boxes, and similar applications.

Japanese and U.S. companies became early leaders in PV manufacturing for uses both large and small. For example, Japanese firms such as Sharp and Kyocera pioneered the use of solar cells in pocket calculators. A credit-card-sized solar-powered calculator from 1983 still helps us do quick calculations.

In the mid-1980s, Germany joined the United States and Japan in the race for PV production dominance, but by the early years of the new millennium, Japanese and U.S. companies accounted for roughly 70 percent of the world’s PV output.

Forward-thinking energy policies in Germany were the catalyst that spurred solar power’s astounding growth over the last decade or so. By guaranteeing renewable power producers access to the grid as well as a long-term premium price for their electricity, the German government’s policy made going solar economically attractive. A reinvigorated German PV manufacturing industry climbed back into the number two spot behind Japan. As world production increased to meet demand, the price of solar panels dropped, helping to drive demand higher.

With demand for PV cells growing quickly, China — factory to the world — got into the game. Beginning around 2006, a boom in the Chinese PV industry massively expanded global production and drove prices down even further. Today China is a solar manufacturing giant, producing close to two thirds of the world’s PV—more than the United States, Japan, and Germany combined.

The decline in PV panel prices over the decades is astonishing. In 1972, they cost over $74 per watt. The average price as of mid-2014 was less than 70¢ per watt—99 percent cheaper. (For reference, the typical U.S. rooftop system today has between 2 and 10 kilowatts of generating capacity. One kilowatt equals 1,000 watts.)

Around the world, solar installations are growing by leaps and bounds on residential and commercial rooftops and in solar farms, also called solar power plants or parks, that can cover thousands of acres. Between 2008 and 2013, as solar panel prices dropped by roughly two thirds, the PV installed worldwide skyrocketed from 16,000 to 139,000 megawatts. That is enough to power every home in Germany, a country with 83 million people. In its January 2014 solar outlook report, Deutsche Bank projected that 46,000 megawatts would be added to global PV capacity in 2014 and that new installations would jump to a record 56,000 megawatts in 2015.

The International Energy Agency in Paris, which is typically conservative in its renewable energy forecasts, has been revising its solar projections upward. As recently as 2011 it forecast 112,000 megawatts of solar generating capacity by 2015 — a figure the world left far behind in 2013. The organization now projects that by 2018 the total will be 326,000 megawatts of generating capacity, but the world will likely come close to this in 2016.

As solar power installations spread, it is worth remembering a point often made in the energy literature to convey the sheer scale of the solar resource: The sunlight striking the earth’s surface in just one hour delivers enough energy to power the world economy for one year.

[Excerpted from the book The Great Transition: Shifting from Fossil Fuels to Solar and Wind Energy, by Lester R. Brown, with Janet Larsen, J. Matthew Roney, and Emily E. Adams.]