Cost per watt of solar panels

Between 2015 and 2023, Facebook kept gaining users while solar panels kept getting cheaper, and the two curves diverged with a companionable precision (r = -0.957) that suggests they have nothing to do with each other in the most thorough possible way. One platform accumulated eyeballs; one technology shed cents. Both arrived at scale. Only one makes electricity.

Facebook's global MAUs grew from 1.55 billion in 2015 to over 3 billion by 2023, while its US/Canada growth plateaued and the international growth carried the platform. Solar panel module costs, meanwhile, fell from about $0.61 per watt to under $0.20 per watt in the same window, a roughly 67% reduction driven by Chinese manufacturing scale and the learning curve of the crystalline silicon industry. Both are stories of compounding global scale — Facebook's network effects, solar's manufacturing curves — driving very different categories to maturity. The inverse correlation is pure coincidence of direction, but both have made the 2020s a different decade than anyone in 2010 predicted.

A feed refreshes. A panel absorbs a photon. Both commodities, now cheap; both, in slightly different ways, unavoidable.