The problem with extension cords is the VOLTAGE (not POWER)
drop/loss. The voltage drops in amount of current times the resistance of the wire.......the greater the current, the longer the wire
and the more 'skinny' the wire, the greater the loss.
Low voltage will dim lights and cause heaters to emit
less heat, but will cause MOTORS (Air Conditioners) to
use MORE current..........that means a possible burnout.
So, get a voltmeter (one that plugs into a receptacle IN
the R V is fine) for a few dollars at WalMart or any
hardware store......if the voltage drops below about
108 volts, turn off something to incease the voltage.
If you do this, all will be fine.