Originally Posted by klem
They can work really well in certain situations and not too well in others. You are going to be in an area where they should work reasonably well. The issues with solar panels are space to put them, cost, and corrosion(this is the same as any piece of marine electronics).
Before you look into panels, the first thing to do is minimize your loads. This could mean switching to LED lights or doing a better job of insulating your reefer or simply being more diligent about turning stuff off. If you have a Link 10 or other meter like that, it will really help with this. The other thing that you have to do is to figure out what your loads are.
Sizing the system depends on what your loads are and whether you want the system to be totally self sufficient or you don't mind running the engine when it has been cloudy for a while. If you don't mind running the engine from time to time, you want to size a little over 100% of your average house load based on the worst month of the year that you will use the system in. If you look online, you can find tables that will show your geographic region and the solar factor(this has a few different names). It essentially is a measure of how much of the panels rated output you will get based on the number of hours of sunlight, cloudiness, changing sun angle etc. Using this factor, you can figure out how many watts of panels you need and from that you can get an area. Take a look around your boat and see whether you have enough area that will have no shading(or at least rarely) and that won't be in your way/you won't step on. If you have enough space, then you can look at cost.
Cost is a function of system size which you determined above. Your major cost is the panels themselves but the wiring and charge controllers are expensive as well.
It is important to realize that the effectiveness of a solar installation is really up to the user. If you get lazy and start increasing your loads, it will not be able to keep up. Also, if you are diligent and keep the panels angled at the sun with no shading, your system efficiency will go up greatly. Angle is incredibly important which is why you see many cruisers with hinged systems. Solar panels work best in fixed applications like roofs because boats have a lot of variables, but they can be very nice if you don't like charging with your engine(who does?).
I will add that we have been off the grid on our boat for over two years. I have found the array one of the very best things I have ever put on any boat, and especially this one. They ar quiet and dependable.
The trick is a propoerly sized array. The thought of getting a little flexible panel or a little 50w panel and eliminating the need for any supplemental charging is a pipe dream. Solar arrays, in order to be sufficient, must be properly sized and must be large.
We found the largest cost was not the panels or charge controller, but the arch to mount it on. Our arch was aluminum. A stainless of comparable size would have been twice as much (and twice the weight). Consider aluminum for this purpose as it will allow you to use a larger diameter arch for wire runs, cost less, and weigh less. It must be a high grade aluminum and should be coated.
Our system consists of four Kyocera 130 Watt panels, wired in series, to an Outback MX-60 MPPT controller. In general, on a mostly sunny day, we can count on over 200ah from the panels. This exceeds our electrical budget. However, on cloudy days, we will not meet our budget or will cmoe close. That is the benefit of oversizing the array for your needs as it will give you more days in which supplemental charging is not needed or minimized.
Hope this helps. Solar is worth it and an awesome addition to the typical cruising boat... but must be designed and sized appropriately.