I've been considering solar for the Scamp for the past three years. It would be nice if there was a magic bullet, a 'one size fits all' solution. Some vendors would suggest that's exactly the case and they'll sell a standard package. Works well if you have the mythical 'standard' RV with the even more mythical 'standard' power demands. A little study quickly showed there weren't any magic answers.
There are some very worthwhile resources that are specifically oriented to RV solar. But even those resources don't always agree. If you're thinking about solar, I'd suggest you start by carefully reading HandyBob's Blog, the section of Jack Mayer's website about RV Electrical & Solar, and the RV Solar Education section on AM Solar's website. Both Technomadia and Wheeling It have done excellent posts about their massive (at least from our perspective) installations and their selection process. They both used AM Solar for their installations.
Doc Wattson meter to track our 12 volt power utilization. This meter can be installed to show power usage or wired in reverse to show power input to the battery, but it can't do both. Eventually, I'll replace it with a more expensive and much more capable TriMetric 2030 Battery Monitor system. A way to accurately measure, monitor, and understand your power consumption is the first step towards sizing an appropriate system.
When boondocking, we don't have any essential requirement for 110 volt a.c. We do carry a 100 watt portable inverter to use with the camera battery charger but everything else is 12 volt or propane powered. We don't have a TV, microwave, or coffee maker to power so we don't have to account for the cost or power consumption of an large inverter. We converted to all LED lighting which is a major power savings and now average 25 amp/hr use each day. We never go over 30 amp/hr, even with extensive computer use and/or daytime heater use. Our power demands are listed on the Scamp 19 page at the top of the blog and are higher in the winter when we're using the furnace than in the summer.
We swapped out the standard Scamp battery for a pair of 6 volt golf cart batteries about 3 years ago, giving us 205 rated amp hours of battery or about 100 amps of usable battery capacity. Our batteries are Interstate brand, simply because that was what Costco carried at the time. We can go four to five days before needed to charge the batteries, but I don't like to haul and mess with a generator to charge the batteries.
With adequate battery and accurate power demand history, it was time to start thinking about options to create our own power. For a couple years we hauled a Honda generator and would fire it up every four or five days to power a high capacity battery charger. The generator didn't get much use, and it was more hassle to haul and store and keep fresh gas in it than I wanted. Of course, if I were based in the southeast where high temperatures and humidity make air conditioning a very high summer priority, I'd be singing a different tune!
For my RV style, (and style is a significant factor in our design decisions) I much prefer a solar system that is permanently installed on the trailer so there's no chance of leaving an essential component in the garage or at a campsite. Nice idea, but our trailer barely fits in the garage now, with only 3/4" of clearance at the top of the door after I taught the trailer to kneel. Self imposed height restrictions, other equipment installations, and preferred trailer orientation when camping all had implications for available roof real estate. I actually thought I had only one possible location until I talked with the folks at AM Solar while we were in the Northwest last summer. One of their staff suggested the location I'm using.
Solar panels come in a variety of capacities, sizes, and efficiencies. My rooftop real estate limited us to a panel nominally 21 inches wide which cut down our options. I seriously considered the GS135 that AM Solar sells, but selected the 100 watt panel from Renogy because of its higher max power voltage (Vmp) and significantly lower price. The 100 watt panel will be marginal in the winter, but should cover us as long as we tilt the panel.
Next up - building a custom mount.