Siemans, had two in continuous use since 1987 and are still giving the rated output havingcompleted two Atlantic crossings. The original guaranty was for 90percent rated output for 10 years. Dont buy flexible panels very short lifespan.
May be worth leaving it if you may be in Portugal, there were some good deals there, others may have more recent info on this, but I think they were vat free.
my siemens 18w is still running perfectly i bought it in 1987!And it spent a few days on a grey mud bottem at 9 meters when i droped it overboard.
I would buy siemens again if i found one.Otherwis i have a BP panel and recently bought a secondhand small 50w of supermarket type.
The BP is rather large as the cells have space around them.So as i have id go for a ridgid mono crystal that is in one large compact block my 50w is only about 3 feet long by less than 2 foot wide and the frame is a bit less than one inch.
I'm going for two Plastimo 80w panels - 1.2x0.5 m. The Plastimo mount allows for an amount of swivelling to follow the sun which increases efficiency. By the way I discovered a rule of thumb for converting watts into a daily amp supply from one of the suppliers I talked to.
Multiply the total watts by a regional factor and divide by the volatge of the panel. The factor is roughly 6 for the tropics, 5 for the med and 4 for UK.
So my two 80w (13.8 A) panels will give about 45 amps in a typical UK summer day or 70 amps in the Caribbean. Hope this helps.
I am a very satisfied customer who followed their recommendations. No other connection.
I knew enough to be able to judge that they knew their stuff and were very helpful in recommending all the other bits and pieces you will need. After sales support is good too.
We have two Kyocera 120s--they've worked flawlessly for the last four years, so we're going to add at least one more--two if we can find the room as they're big babies (though now I think they only make the 130). Siemens has an excellent reputation, but they were more pricey than the ones we bought. So far, no worries and we have them rail mounted so they can be adjusted.
We also have 2 Kyocera 120w panels. I chose this brand because they were the only one I could find that specifically covered marine use in their warranty. Many of the others only cover domestic/land based use as part of their 10 or 20 year warranty.
If you get panels make sure you get a MPPT controller (maximum power point) which effectively gives up to 25% more power than a standard controller that limits their output to the battery voltage at the time. MPPT is like a solid state transformer that will let the panel work at its maximum output voltage (17.5V in our case).
Also make sure you mount them where they are completely clear of shadows. Even the shadow of your backstay crossing over 2 or 3 cells can drop output by 20% or more. Putting them on deck where the boom can shade them is a complete waste of money.