240V. Since we're throwing around numbers, let's be accurate. This is a pet peeve of mine. We've been standardized at 240V since 1967, and it was higher than 220V years before that.
Thanks for the correction about the actual voltage today.
However, it seems like 220V was the standard before that [1], which is why it's still common parlance, referring to the "higher" voltage. Certainly I've heard many people in the trades still refer to it with the older term, even if the circuit is actually 240V.
The voltage started at 220 way before the 60s, and then increased incrementally over the years, until standardizing at 240V. I don't know when the first bump past 220 happened exactly, and it may not have been simultaneous in all areas. I gather the reason for the standardization was to stop the creep and pick a voltage to stick with for everyone.
However, it seems like 220V was the standard before that [1], which is why it's still common parlance, referring to the "higher" voltage. Certainly I've heard many people in the trades still refer to it with the older term, even if the circuit is actually 240V.
1. https://en.wikipedia.org/wiki/Mains_electricity#History