For one thing, the price of solar is falling, and rapidly. In a March 2011 post for Scientific American’s website, Ramez Naam, a computer scientist and technological enthusiast, compared the rapid progress of solar power to Moore’s Law, the famous dictum that described the process by which microchips grew steadily more useful over time, doubling in efficiency every two years. The price of solar power had fallen in two decades from nearly $10 a watt to about $3. By 2030, he predicted, the price could drop to just 50 cents a watt.
Four years later, in the spring of this year, Naam revisited his post and admitted his prediction had been wrong. It was far too conservative. The price of solar power had already hit the 50-cent threshold. In the sunniest locations in the world, building a new solar-power plant now costs less than coal or natural gas, even without subsidies, and within six years, this will be true of places with average sunlight, too. Taller turbines, with longer and more powerful blades, have made wind power competitive in a growing swath of the country (the windy parts). By 2023, new wind power is expected to cost less than new power plants burning natural gas.