Nominal mains voltage (Europe)

Continental Europe historically ran at 220 V and the United Kingdom at 240 V. Rather than force either side to re-engineer, CENELEC harmonised on 230 V in 1987 with an asymmetric tolerance wide enough that no existing installation had to change a thing: the standard admits 230 V +10%/−6%, later widened to ±10%, which brackets both old values comfortably. Measure a European outlet today and you will often still read close to 220 or 240 depending on where you are standing.

Doubling the voltage relative to North America quarters the current for a given load, so a 3 kW kettle draws 13 A instead of 25 A and can run on ordinary house wiring — which is why European kettles boil faster and why thinner conductors suffice for the same delivered power. The trade is a higher shock hazard, addressed with recessed shuttered sockets and mandatory residual-current devices. Three-phase supply to homes is common, at 400 V line-to-line.