Solar Power

Something to keep in mind is that partial shading will prevent an entire solar panel from producing any useful output.  So if one corner of the panel gets some shade, its as if the entire panel is in shade.  This is due to the internal series wiring of the individual cells - when one cell is in shade it acts as a resistor and so it blocks the current from the other cells.  If you often camp - or store the camper - where you can't get the panel(s) in full sun most of the day you should reconsider using solar.  Often just buying a 2nd battery is the cheaper and more reliable option for a week-long trip, and/or using your tow vehicle to top off your battery every other day for a half-hour (use jumper cables and make sure to start the vehicle before attaching the camper battery).

 Local Harbor Freight has this same solar set up on sale for $199. Regular price is $249. They had this for for last black friday 2009 sale for  $150.

Myself, I don't trust Harbor Freight to anything near good quality.

Terry 

That would be 45 watts per hour in full sunlight.  You can look up the "solar insolence" for your area by searching the net (one resource is below).  Around me in MD its about 4.5 hours per day average, which means year-round you can count on 4.5 hours of useful sun.  You'll get more during the summer when you are camping.  Let's say its 6.