Question: what is the maximum acceptable supply voltage tolerance for a 120 volt circuit?
Answer: The national standard in the U.S.A. is ANSI C84. 1. Voltage regulation requirements are defined in two categories: Range A is for normal conditions and the required regulation is ± 5% on a 120 volt base at the service entrance (for services above 600 volts, the required regulation is -2.5% to +5%)