Remember, Outlets in a house or Garage area are NOT the ONLY outlet being supplied by the supply 120 romex line. Doubtfull that the 15 amp outlet you plug into is the ONLY outlet connected to the Breaker. So, while 15 amps is indeed all you need to keep the RV maintained as you require, what happens when you plug a 120 appliance into one of the other outlets in the daisy chain of that 15 amp outlet? Also, I would replace the outlet(15 amp receptacle) with a 30 amp plug and label the plug 15 amps MAX. Better to plug the RV 30 amp plug into the correct receptacle than adapting down from 30 to 15. 30 to 15 amp adapters are notorious for heating up and deterioating and not having a GOOD TIGHT connection. Doug