My last boat had 200 watts of solar charging
to maintain 4 golf cart batteries (house) and a seperate flexible panel to maintain the starting battery
. The house circuit was always full unless the refrigeration
ran for several days in cloudy conditions which are common in New England
Only once in three years was it necessary to start the engine
to augment the solar panels. I have since sold that boat, but am gathering the equipment
necessary to outfit my new boat which should be here in a month or so. I will add 320 watts to the new vessel to ensure that there is no shortage of power since our days are shorter and less sunny than our counterparts to the south.
In the winter, I leave all the navigation
instruments on to keep the LCDs from freezing and going south. It is easier than removing the instruments as so many do. I generally disconnect all but one of the solar panels for the winter. The remaining solar panel is sufficient, even with the ice and snow that collects on the panel to keep all the batteries fully charged.