We find solar panels are rather over rated. We have two 55 watt panels and they produce enough power to run the fridge as long as we get good sunny days. They have numerous weaknesses
a) ANY shade across the panels (shadow from mast, halyards,
lazyjack lines, bird droppings, whatever) or cloud seriously reduces or even eliminates the output.
b) extra panels are heavy, expensive and they only work for about six hours a day IF it is sunny.
c) even suppliers have advised us that wattage on most panels is over rated. That is 120 watts of panel will never produce 10 amps on a 12 volt system - 8 if you are lucky and conditions are perfect.
We find with a freezer (cooled by water
pump), hydraulic
autopilot,
lights and a laptop used for navigation and digital TV reception we use about 100 amp hours per day more than the solars produce. That means we have to run our 110 amp alternator for about 1+ hrs per day to maintain power, more if the solar panels have been limited by cloud etc.
Currently looking for a wind generator as more panels will still have same limitations but a wind generator will work whenever the wind is blowing. There seem to be two different styles. The three bladed feathering prop versions only kick in at about 12+ knots but produce more power when they are operating BUT they are incredibly noisy. The multi blade versions work at lower speeds, are silent, but produce less power for same wind speed. Typically four amps at about 15-17 knots.
Price seems to be equivalent to a single 110 watt panel. We are currently looking at a Rutland 913 made in the UK. Any one tried it?
Not sure if any of this helps but would love to hear what others have experienced.