
In the U.S.: we use 120/240.
Since our electric system originally supplied 110 volts that value became embedded in people’s minds and a lot of people still refer to our system as 110/220. Since we used 115 volts for about 50 years a lot of people have that in their minds and still refer to our system as 115/230. But those days are long past. The U.S. is now 120/240 volts.
Most electric motors and many electrical appliances (especially those with motors) have a nameplate rating of 115 volts (meaning that they’re designed to run optimally at 115 volts). This is because they expect that if the utility supplies you with 120 volts at your main electrical panel there will be less than that by the time the current travels through your wires to the appliance. This is due to voltage drop.
Steve Nations, Mechanical Engineer, Home Inspector