Energy demand and costs: Swanson's Law

Graph below shows the distribution of energy demand in the US, from wood burning at the time of independence to gas and oil now.

Renewable sources are still a small share. But there are good news in that front, with solar energy prices falling at a fast pace. According to The Economist, "Swanson’s law, named after Richard Swanson, the founder of SunPower, a big American solar-cell manufacturer, suggests that the cost of the photovoltaic cells needed to generate solar power falls by 20% with each doubling of global manufacturing capacity." Hope springs eternal.