Originally Posted by sailingdog
I guess a lot of it has to do with what you're running on your boat, and the design and efficiency of the refrigeration. I have relatively modest electrical use on my boat—a small DC refrigerator, a stereo, a VHF, running lights, cabin lights, a laptop computer—and I find that solar power is more than adequate for my needs. .
It's also a function of your battery capacity and your cruising style. I was having this debate with a friend of mine with a similar steel full keeler. He was thinking that when he upgraded his engine, he would run two 100 amp alternators to get a rapid charge on his battery banks. This is a man who likes his toys, mind you.
Our energy needs are more modest. While we have a 2000 watt inverter, I am going to simply get a bigger battery bank than most people (probably three 8D AGMs). I will charge this on the hook with solar and will carry a Honda 2000 gas generator for running power tools and if necessary to charge the banks. I figure that the key to not running the alternator to produce electricity (which I consider noisy and inefficient) is to have a modest energy budget in the first place (that means fridge, but not a lot else while stationary), and to seriously gear your stays to your passagemaking.
By this I mean that if you expect to be on the hook for a week in some tropical paradise, have enough capacity (with solar charging) to defer running the diesel until you decide to up anchor and go to the next place via *motorsailing*. Then you can run the diesel *under load* efficiently and get your charge on for much of a day, say, while blowing fumes, heat and noise in your wake. Then you can return, if you wish, and get a rep as "the quiet boat".
This is possible for us, of course, because of the nature of our boat and my actual desire to keep a half-ton of lead on either side of the engine room for ballast purposes. But it's not a crazy idea for many cruisers to carry more amp-hours that can give them more of an ability to burn diesel to turn an alternator.
Of course, along with energy budgeting (that plasma 42" LCD has no place aboard, does it?) is the idea of better or even extreme insulation, meal planning that doesn't rely on refrigerated foods, and just saying no to ice cubes that cost a buck a litre.