Whether you are keeping the batteries from going dead or running your alternative lifestyle, solar panels on a boat make a lot of sense. Most of us are not willing to live without the comfort and safety afforded by electrical power. Creating that power from fossil fuels can be expensive, smelly, loud, and inconvenient. Solar power is silent, reliable, environmentally correct, and in most cases cost effective.
Solar vs Fossil Fuels Making all of your electrical power from a generator or high-output alternator on the auxilary engine will be much more expensive than getting it from the grid. A typical cuising sailboat uses about 150 a amp-hours per day (Ah/d). If you were getting this power from the grid (like at your house), this would cost about $0.20 per day. If you make this amount of power with fossil fuels, just the fuel alone is likely to cost over $1.00 per day (and require that you carry additional fuel or top off the tanks more often). If you add maintenance, depreciation, and repairs that could easily go to over $2.00 per day, and that doesn’t consider the noise, smell, etc. With solar there is virtually no maintenance (maybe cleaning the bird pooh off occationally). Solar modules will last a long time, probably more than 40 years. The warranty is typically 20 – 25 years. Figure the cost of the solar at $6 watt (including the controller and installation equipment), and the break-even point compared to fossil fuels is about 3.5 years.
Other Advantages But wait, there’s more; solar does not polute. Solar is much more cool (it doesn’t heat up the boat). Batteries prefer to be charged at a low rate over a long time, compared to the high rate for short time from a high-output alternator or generator, which can overheat and shorten their life or even damage them. Your batteries are more likely to get fully charged with solar, because when charging in a short time from fossil fuels, they typically do not accept the last 10% or so of the charge, and they are likely to not get cycled as deeply with solar, making them last longer.
The Down Side Cost. At $6 per watt, a typical system for an offshore cruising boat would cost about $2700. But, unless you have a catamaran or have a generous sized arch, you probably do not have room for the all the solar modules needed. Also,if your boat already has a high-output alternator or gen-set, then you will have little in the way of avoided cost, at least for the initial investment.