I don't know but Nigel Calder's book has a really good section with form to fill out and is how I calculated mine.

Sam. Here is what we have and it works well. I have 240 watts of solar and a kiss wind gen. I have everything led and our fridge draws 5.4 amps. That is our biggest draw. We have been living 5 to 6 months on the hook the past 4 years. With out the wind gen I could not make it with out running the motor. With what we have we usually can set for weeks at a time with out any extra need to recharge the batteries. I would say 200 watts is to small if just solar and not using the Honda.

A 100W panel, installed horizontally on a bimini, will yield anywhere from about 10Ah - 34Ah per day. Two of them should be able to deliver 20Ah - 68Ah each solar day. Sure some days you may exceed 34Ah per panel but this would be a super optimal day. This is of course assuming a top-notch installation with minimal voltage loss in the wiring and an MPPT controller set up to get the most from the panels.

Be aware that semi-flexible solar panels, other than Aurinco, Solbian and Gioco, are made in China and are of rather questionable quality. They most often utilize "orphan" solar cells no one else wants and they are often riddle with "micro-cracking" right out of the gate.. If you want to buy a Chinese knock-off most of them all come out of the same factory and have numerous brand names slapped onto them so buy from a company that will stand behind the product. ALWAYS test these panels before installation to ensure they are meeting spec. I test lots of Chinese semiflexible panels and a good chunk of them do not meet spec.

If price is an issue I would urge you to consider going rigid frame panels...

Even if your PV cells were able to deliver 12 amps peak (about 60 ah/day), please be aware that figure is only valid for a system that can 100% utilize that power.  As your refrigerator cycles on and off and your batteries come up in SOC, the draw power will be mismatched to your PV output.  You also have to allow for cloudy days.  If you have one cloudy day, not only does your battery bank have to support the entire load, but the following sunny days have to make up for the missed day.  This means that you have to substantially over-design your system if you expect to rely 100% on PV.  200 watts will not allow for these variables.  Much better to have a PV system that delivers high amounts of energy to allow the batteries to come out of absorption before the end of the the day AND support the on/off cycle of the refrigerator AND be able to make up for missed days.  Assuming you have a high capacity house bank, 300 watts would be a bare minimal starting point.  But one cloudy day and you'll be in unrecoverable deficit, so add another 100 watts for this scenario.  BTW, I've never met anyone who said they had excessive PV capacity....

The sheer reality of solar on monohull cruising boats (a real estate issue) is that unless you use your alternator or other source to punch through bulk charging there is rarely enough solar hours in a day to recharge a lead acid battery to 100% SOC. So each day the usable capacity walks down a bit unless you help the solar along.

A basically brand new Trojan flooded battery, when charged at .15C, still takes approx 7 hours to hit 100% SOC from 50% SOC. Even expensive AGM batteries, in good health, can take 5.5+ hours at high .2C and .4C charge rates. As batteries age & sulfate the charging process takes even longer. As was mentioned above you can't go too large with solar...

For a bit of perspective a .15C charge rate on a 450Ah bank would be a charge current of about 68A. This 7 hours assumes no "premature floatulation" as most solar controllers and smart chargers will do. Premature floatulation only extends the time it takes to get back to 100% SOC, when we drop to float before the battery is actually full.....

The 3 80 watt panels i have are Kyocera. They are hard framed and mounted on a bar 12 inches our 
hard bimini. That way I am able to tit them to just a bit extra  amps. Just like now I am in St Augustine and making power thru the night. It is nice to the other comment's.

Sam. I should have added that I do believe those 80 watt panels are not made no more.

I haven't sprung for a solar system but I've paid more and more attention to boats in my marina that do have them.

One popular configuration is to mount on the bimini plus the cabintop or dodger and on folding mounts attached to the stanchions. You have the issue of shade from the sail and boom on one side of the boat, which means that you aim for a system where either port or starboard will give you the necessary amperage, and then at anchor you have the entire overbuilt system to really top off your batteries.

This does have the downside of being expensive... But it seems to be what the solar serious small-boat monohull sailors go for. 

Here are the pictures I promised.

One shows the four solar panels.  I got the stainless steel supporting mounts from EMarine Systems in Fort Lauderdale. 

Another shows one of the middle supporting strut (angling down from the center of the wooden piling to the right side of the ropes) and gthe forward supporting strut on the far right edge of the picture.  It attaches to the upper part of a stanchion (not shown).

The third shows the aft supporting strut at the far right edge of the dinghy.

As you can see, there is room for another four which would bring me up to 800 and I think the beefed up bimini frame will hold the weight ok in all but a major storm (in which case I plan to take them all down).

 

Panel frame pic

Other panel frame pic.

Other panel frame pic.

Just thought I'd share my solar panel installation.

Picture speaks for itself.

Bill Matley

Very nice!

When we were on our annual spring cruise, we noticed a semi flexible solar panel installation. They were mounted directly on the bimini by zippers sewn on the edges of the panels and on the the bimini. This process avoids the "oil derrick" appearance of additional stainless brackets and gives a very clean appearance. We have been in contact with Emarine in Ft. Lauderdale which has designed a system using 2 95 watt semi flexible Gioco panels and a Blue Sky MPPI controller. The panels would be sufficient to meet our 60 amp daily requirement and would be located in front of our split backstays. We have been told that the shading at times from the backstays is not the problem it once was. What experience have any of you had with shading, i.e. sharp shadowing or diffused shadow line? Another option would be 2 75 watt panels located to the outside of the backstays. In addition, we also came across a Catalina that went the Defender route with the 2 100 panels that Sam was considering and used velcro to attach them to his bimini. He was pleased with their performance. He came all the way down from New York, mostly on the outside, and had no issues with the installation.