Depending on your layout, it could be a real bear running a wire from the 2nd A/C back to your existing breaker box, then upgrading the box to the larger 50A model, plus adding storage for the fatter 50A cord. I'm with you, that's the way it should be done, but how much are you willing to pay? It just may not be practical. As BB mentioned, many on the forum have added a similar set up to run a space heater or add a second space heater. So you would have 2 shore power cords, your 30A and a separate 20A feeding the 2nd A/C.