In the US and Canada, 220 volts, 230 volts, and 240 volts are used interchangeably to describe one voltage range that is used to power larger appliances. Similarly, 110 volts, 115 volts, and 120 volts all refer to the one voltage range that is available through the common electrical outlet. The sources of these seemingly different numbers are as follows:
The 220 volt and 110 volt designations are older and familiar terminology, but are no longer used in either product design or by electric utilities in the US and Canada.
The 230 volt and 115 volt terminology comes from equipment design standards. Equipment is commonly designed to operate at 230 or 115 volts plus or minus 10%.
Electric utilities typically deliver electricity, under standard conditions, at 240 volts and 120 volts plus or minus 5% at the transformer.