Encouraging reports keep emerging about growth prospects for renewable energy. The International Energy Agency’s November report, Renewables 2020: Analysis and forecast to 2025 , projects that by 2025 electricity from renewable sources will surpass that from coal, the world’s biggest and dirtiest power source. Also last month, Max Roser, writing in Our World in Data , became the latest journalist to report that in most parts of the world, new wind and solar generating stations can make electricity more cheaply than new plants powered by fossil fuels. The common driver behind both developments is renewable technologies’ impressive learning curves. Each doubling of cumulative installed capacity has brought a constant price decline, which Roser pegs at about 20% (see chart). The upshot, say Roser and others, is that large investments into scaling up renewable technologies will pay off with still cheaper prices, driving a “virtuous cycle” of ever-cheaper wind and […]