The voltage from your inverter is a little different than the voltage in your home. The voltage in your home is called a “sine wave”, while the voltage from the inverter is a “modified sine wave”. Because of this difference, you will need a meter that measures “true RMS” voltage. If your meter does not measure “true RMS”, then it will read low.
If it does not say “true RMS” on the front of your meter, then it is not a true RMS meter and it will read low.