Michael - I had understood this to be a function of solar panels in general, not just some - but admittedly ours are 9 yrs old so maybe technology has improved ? I was about to post in similar vein to you and say our solar panels have been excellent both in terms of charging and value. Ironically altho you say "except in UK waters" we have found even on cloudy days we get some charge - we were told by the manufacturer that the panels perform less well in hot conditions so our lovely UK weather helps keep them cool ! If you were off to warmer climes tho like dazAutomatics (lucky things) it is another reason for mounting the panels on a stern gantry as you (and we) do - to allow air circulation

Penny