I have enjoyed your Pacific Yachting Tech Talk articles as they are not condescending or preachy. I have also been reading about the Gioco panels you distribute. My interest is twofold. I would like the benefit of solar charging while cruising and secondly, I would like to be more independent of shore power in our Marina where I have recently experienced "issues" from being connected to its AC shore power. We have owned our current boat for a year and replaced our zincs this April when they were 8 months old and half gone. I recently dove under the boat while out at anchor and was shocked to find the prop and shaft zincs were 95% gone after 90 days! We have a Beneteau 36 center cockpit with a full bimini that I think would make a great location for one or two of the flexible monocrystalline or polycrystalline panels and an MPPT regulator. I do not quite understand the distinction between the two types. If one panel was used now, can a similar sized second panel be added in parallel at a later date? If so, is an MPPT regulator available for the demands of two such panels? The distance from Bimini to batteries is about 10 feet; what gauge wire would be required?
Solar power is a great addition to many cruising sailboats. As you mentioned, it is really handy to deal with troublesome AC at marinas as well. In our case, we do not actually need to plug in at the dock in the summer, even with the fridge running. The Gioco GSC (monocrystalline) line provides more power for the same surface area as the GSP (polycrystalline) line. Mono panels are designed for boaters with limited space that require the maximum output per panel and, as a result, mono are more expensive than poly.
To your question, you can install one panel today and then install another later. In similar situations, I would recommend leaving space to accommodate more panels in the future. For efficiency, we have always recommended installing a dedicated panel per controller; this guarantees that each panel is producing the maximum output. In terms of wire, a gauge 10/2 wire would be sufficient.