[The Economist] Sun Machines: Solar, an energy source that gets cheaper and cheaper, is going to be huge

> Over the course of 2023 the world’s solar cells, their panels currently covering less than 10,000 square kilometres, produced about 1,600 terawatt-hours of energy (a terawatt, or 1tw, is a trillion watts). That represented about 6% of the electricity generated world wide, and just over 1% of the world’s primary-energy use. That last figure sounds fairly marginal, though rather less so when you consider that the fossil fuels which provide most of the world’s primary energy are much less efficient. More than half the primary energy in coal and oil ends up as waste heat, rather than electricity or forward motion.

>What makes solar energy revolutionary is the rate of growth which brought it to this just-beyond-the-marginal state. Michael Liebreich, a veteran analyst of clean-energy technology and economics, puts it this way: **in 2004, it took the world a whole year to install a gigawatt of solar-power capacity (1gw is a billion watts, or a thousandth of a terawatt); in 2010, it took a month; in 2016, a week. In 2023 there were single days which saw a gigawatt of installation worldwide. Over the course of 2024 analysts at BloombergNEF, a data outfit, expect to see 520-655gw of capacity installed: that’s up to two 2004s a day.**