What voltage range should be used when using a digital volt meter or digital multimeter to measure standard house voltages in the United States?

If your meter lacks an auto-ranging function (many inexpensive units lack such a feature), you must set the range so that the maximum value is greater than the conventional voltage levels in your house. In the United States, the common voltage level is 120 volts RMS, although many homes are equipped with 240-volt service, to accommodate certain appliances, like clothes dryers. (The 240-volt service is really two 120-volt legs.) It's a good idea to set the range higher than expected initially and then adjust it down once you've determined what ballpark you're in. This practice protects you and the meter from dangerous, unexpected over-voltage conditions.