Depending on where you get the power for your house, (power company) you can't always depend on getting a static voltage to your main panel. The voltage can go up and down in your neighborhood as well. (that can effect the voltage at your panel) After your AC has been running for a few hours, it would be a good idea to check the voltage at the input of your main panel and compare that to the voltage DROP you are seeing inside your RV.
That way you will KNOW the voltage drop from your panel to the RV which could be important as summer gets in full swing and the power demand in your neighborhood goes up. (the available voltage at your panel may go down) I've seen line voltages (from the power company) fluctuate at as much as 15 volts on a 120 volt nominal residential service.
Chum lee
