This really depends on your air conditioner model. You should always check with your local RV dealer or do your own research for the A/C units’ start-up amperage and the power it needs to continue running. Most roof Air Conditioners kick-on at 16-18 amps, and
draw a steady current of 12-15 amps. If you are plugged into a 15 amp outlet, it will most likely trip the
breaker at the plug/source, even if you do not have any other appliance on.
Also…Just because your unit is running doesn’t mean that it is getting enough power. You can find many occasions on the internet where low voltage has cause A/C units (and the adapter) to burn out, and never trip a breaker.
If you do plan on running an A/C unit, you would want to consider using a 10 Gauge 15A Extension Cord with the step down adapter for your RV. Listed below are the two most common step down adapters you may have to use on your RV.