Voltmeters “fresh out of the wrapper” have a range of accuracy, and taking the time to understand that characteristic for digital instruments measuring AC voltage can keep a foot out of your mouth.
Many utilities have their ‘service conditions’ or ‘electric rules’ posted on their websites. A North American standard that is often cited is ANSI C84.1, but a state PUC may mandate tighter extremes than published in C84. For a 120-volt base, usually 126 or 127 volts is the upper [sustained] limit, but certain regions limit it to 125V.
If a trouble guy comes out to check voltage, ask to compare your readings to his with both meters simultaneously connected.
