If your RV air conditioner unit has an integrated heat pump, then it is possible to heat your RV with your air conditioner. However, if you are using a rooftop air conditioner, you may find that the heat pump is not the most effective way to heat your RV. This is because heat rises, so the warmer air will be created at roof level and will stay there. You also need to be aware of the heat pumps working restrictions, including the temperature range at which it is effective. If you are traveling in areas where the temperature is regularly around freezing, then your air conditioner heat pump is unlikely to be effective at all. A secondary heat source is always a good idea.