How to Measure Outlet (Line) Voltage

To measure the voltage at an electrical outlet requires the use of a suitable multimeter. Do not attempt this measurement without the proper tools and precautions.

CAUTION: Working with a live electrical outlet can be very hazardous. Please read our safety precautions, disclaimer, and Terms of Use before attempting any testing or repairs.
  1. Set the meter to an AC scale capable of measuring the respective AC line voltage for the model being diagnosed.
    • Typical voltage in residential homes and business offices in the US should range from 110 to 120 volts AC.
    • Some commercial and industrial microwave ovens use voltages from 208 up to 220 to 240 volts AC. These can be identified by their different slot configurations.
  2. Carefully grasp the insulated portion of the probes (do not touch the metal probe tips during testing and do not allow the probes to touch each other) and place one probe into each of the two slots as shown.
  3. Note the voltage reading displayed on the meter
  4. Gently remove the probes, being careful not to touch the metal part of the probes to anything or to each other.
  5. If the voltage is more than 10 percent below normal, the problem may need to be referred to a professional electrician or the local power company. This is especially significant during hotter months, when line voltage tends to be lower.
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