For us it had nothing to do with being Green. It was all about self-sufficiency and comfort.
The first thing you need to do is quantify your
electrical needs/wants. This will depend on two things:
1. Lifestyle/comfort level: small
refrigerator? Big one? None?
Watermaker? Hot
water shower every day? computer?, etc.
2. The specific
equipment on the
boat you will be cruising - eg. Halogen lights will use more
power than fluorescents and fluorescents will use more than LEDs and
solar garden lights use none at all. Until you have the
boat you want equipped the way you want, the best you can do is an estimate of average demand on the boat with the
equipment you think you will have.
Once you have a fair idea of what your demand will be, you can try to calculate what wind/solar equipment would be necessary to meet all or some of this demand and whether you can fit it on the boat you intend to use. How practical the result is depends in part on where and when you go. Becalmed in a
fog bank off the coast of
Maine, you either run down the
batteries, fire up the engine/generator, or go without power. OTOH, your
refrigerator will use less power on the
Maine coast than it will on the Venezuelan coast.
FWIW, our
electrical demands for our lifestyle were about 50 to 80 amps and we were fairly consistently able to meet them with
solar and
wind (360 watts
solar panels and KISS wind generator) in the
Bahamas and
eastern Caribbean where there is a lot of sun and wind.