This one the dealer was discussing actually comes with a 150w installed. He was talking about adding an additional 85w to the 150w. All said, I'm likely going to wind up with the trailer that is all set up with the quick connects and the 10w maintainer. Based on what I read @ http://www.rvsolarelectric.com and what you fine folks are suggesting I think two 100w panels and the fancy controller might be a good starting point. Not sure I'm gonna get much more on the roof. The trailer is a 20' box. Less than 24' hitch to bumper. Once I get the trailer in my yard I will add up all the amp draw and to the job right. I really don't plan on using the heater during the day. At least that would not be the norm. I don't really consider us to "fair weather campers" but I am not really intending on going any where that is less than 10 degrees for any real length of time.