There have been recent posts concerning how to monitor the AC voltage, either from shore power or the generator. I personally use a very old but efficient analog meter plugged into an outlet which can be viewed from the entry door.
However, some folks with a more modern approach may like the digital style item in the following post:
Amazon.com: DROK 90538 Flat Plug AC 80-300V Voltage Panel Power Line Volt... (https://smile.amazon.com/gp/product/B00CDJRLKI?ref=em_1p_7_im&ref_=pe_3780190_507059070)
Hey, that's a nice little unit at a low price. Thanks, Steve!