We've seen a few with a framed panel but I really like the idea of the flexible panels that are stuck down to the roof of the boat. They are much less obtrusive and less likely to get broken, but they do appear have a shorter life span. There is another compromise with the flexible panels and that is being unable to angle them to the sun.
This website includes prices for flexible panels :
I also came across this company that uses solar energy to deal with damp issues. The cost for one of these dehumidifier units on a narrowboat is around £350. They are a great idea for boats being left over Winter.
|Dehumidifier unit solar panel|
For further information I've found about all types of solar energy on narrowboats :