A/C - roof unit, portable, or swamp cooler?

[kagorall]

Hi. I purchased a 1977 Argosy 24' last year to help a friend of mine start a new life. She recently moved into it full-time in the Fort Worth, Texas area. It's really hot there now (100 degrees), and she has no shade where she is located. She discovered that the roof unit, which she thought was an air conditioner, is only a heater. She needs air conditioning as well because the heat it making her sick.

At first she thought of getting an evaporative (swamp) cooler. From what I've read, she would have to keep supplying it with ice, which doesn't seem practical. I think it's often very humid there also. Then she thought of replacing the roof heater with a new heating and cooling unit. I've read that it's better to keep an original roof unit rather than remove them. Now she is looking at portable A/C units to keep inside the Argosy.

Which of these approaches do you recommend? Can you give me an idea of how much power an A/C unit draws? My friend is located next to her sister's house, which she plugs into, and I told her to expect to pay a high electric bill. Do any of you have recommendations for a specific unit - one that would serve the purpose and be relatively quiet and presumably energy-efficient?