Swanson's law

Swanson's law is an observation that the price of solar photovoltaic modules tends to drop 20 percent for every doubling of cumulative shipped volume. At present rates, costs halve about every 10 years. The Law is named after Richard Swanson, the founder of SunPower Corporation, a solar panel manufacturer. Swanson's Law has been compared to Moore's law. Crystalline silicon photovoltaic cell prices have fallen from $76.67 per watt in 1977 to $0.36 per watt in 2014. Plotting the module price (in $/Wp) versus time shows a dropping by 10% per year.

As of the end of 2016^[update], the U.S. had 40 gigawatts (GW) of installed photovoltaic capacity, having almost doubled in capacity from the previous year. In the twelve months through March 2017, utility scale solar power generated 38.3 terawatt-hours (TWh), 0.94% of total U.S. electricity. During the same time period total solar generation, including estimated distributed solar photovoltaic generation, was 59.8 TWh, 1.47 % of total U.S. electricity. Based on this trend, solar could contribute 20% of total electricity consumption by 2030.

The term Swanson's Law appears to have originated with an article in The Economist published in late 2012. It is a misnomer in that Swanson was not the first person to make this observation. The method used by Swanson is more commonly referred to as learning curve or experience curve analysis. It was first developed and applied to the aeronautics industry in the mid-1930s, and saw its first widespread application to the photovoltaics industry in the mid-1990s.

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