WHEN A COLLEAGUE from this newspaper visited Sam Altman in 2022 at his home in San Francisco, he noticed two pairs of pink high-tops on a bookshelf. One had the logo of Mr Altman’s machine-learning startup, OpenAI. The other bore an emblem for Helion, a nuclear-fusion company that Mr Altman also backs. The entrepreneur is obsessed with both technologies—not just as foot fashion. He believes that the cost of intelligence and the cost of energy will fall in a mutually sustainable way. He calls it a “long and beautiful exponential curve”.

Nasty, brutish and short, more like. Talk to utilities and data-centre operators and, though many share Mr Altman’s excitement about artificial intelligence (AI), they are grappling with an energy conundrum on which the future of three big economic shifts partly hinges: the AI revolution; the efforts to electrify swathes of the economy; and the fight against climate change. In a nutshell, “generative” AI, the sort behind OpenAI’s ChatGPT, has a ravenous appetite for electricity. It has landed, virtually out of the blue, on a global energy system that is already struggling to cope with alternative sources of power demand. As yet it is not clear whether there will be enough clean energy to meet everyone’s needs.