for what its worth from my experience over the last 4 years cruising. We have 2x 135W kyocera panels which by the book put out 7.4amps each but over summer in sunny northland we were getting 18.5amps out of them so pretty efficient. with 450amp/hrs of batteries we were able to run the fridge 24/7 for 6 weeks, autopilot, plotters, tv, radio, inverter running toaster and all sorts, watermaker for hours a day (got to the stage we were making so much water we were filling buckets to wash dive gear and the boat deck). the only thing to take into account is the sun has far less energy in the cooler