For solar power on vessels, there are really only two parameters, viz.
(1) maximum output per limited footprint and (2) maximum output under limited light conditions.
SunPower are the clear market leaders. SunPower cells are 'officially' rated (under lab conditions) as the most efficient available, but perhaps just as importantly for boats the SunPower cells are also the best under limited light (e.g.
sun low in the sky or overcast) conditions.
The next choice is between the hard and soft panels. The hard panels provide both more power per footprint and they are much better value. SunPower hard panels are also proven performers at sea. We use 2 x SunPower E20 panels (327W@) on CatNirvana
and they are brilliant. SunPower panels also powered the global circumnavigation
on solar power alone by Turanor Planetsolar
Sep 2010-May 2012. You can read more about SunPower at sea here...
So SunPower rules and, if you have the room, the hard panels are a very attractive choice.
Unfortunately, SunPower do not make soft panels, but SunPower cells are available in soft panels from two manufacturers, one Italian (Solbian) and the other (Solarplex) Chinese. The soft panels are appealing for their ease of installation
, but they are seriously more expensive. Some soft panel users note issues/problems with wear ability and at least one rep for the Solarplex panels suggest they will be subject to early de-lamination.
You should also (as suggested by kentobin) familiarize yourself with MPPT
controllers as these are really worthwhile, if not necessary, for any solar at sea setup...and take your time doing your research
We agree as well with both rebel heart and Albro359. Fit as much power as you can -- We're back to that power per footprint parameter! -- and expect that putting yourself into solar at sea can be a pain, but silent power is certainly worthwhile!
If you're around OZ and interested in the SunPower E20 hard panels, we'd be happy to source your panels and MPPT controller -- We are a small business and we only market what we use ourselves -- and we always look after CF Members price-wise.
In any event, we wish you well in your search!