{If artificial-intelligence models have a hometown, it is probably Ashburn, northern Virginia, just outside Washington, DC. Attentive window-seaters flying into Dulles airport might notice a clutch of white-roofed boxes jutting out next to rows of suburban culs-de-sacs. Those data centres are part of a cluster—the world’s biggest—which last year guzzled more than a quarter of the power produced by Virginia’s main electrical utility.}