How to Size Solar Panels for a Cruising Boat

How to Size Solar Panels for a Cruising Boat
Keeping your battery recharged with the sun is a viable alternative for a pure sailboat, or even an auxiliary sailboat or power boat, when you don't want to use a generator to keep the lights on and the batteries charged -- as long as the solar panel you use is sufficiently large to compensate for the drain on your batteries that comes from every instrument, appliance, light, pump or toy that draws an electrical breath on your boat. A near-exhaustive inventory of each potential drain on your battery and a bit of math are all it takes.

Instructions

Difficulty: Moderate

Step 1
Take an inventory of your electrical system and find out exactly what it provides power to. Make a list with pen and paper -- this list will vary from boat to boat, but some common drains on your power source include water pumps, lighting, GPS, fish finder and refrigerator. Take note of the power rating of each item, usually clearly marked in the same plate or label as the serial number.
Step 2
Multiply the power rating for each item (use a calculator) by the time it's likely to be used each day. If you have a 100-watt light bulb that you expect to leave on two hours a day, 2 times 100 equals 200 watts. Make a list of the total watts used.
Step 3
Add up the wattage used on your boat during the day and divide the total by 5; solar panels require five hours to recharge your batteries. For example, if your total electric use for a day equals 500 watts, 500 divided by 5 equals 100. You'll need a 100-watt solar panel to keep your battery charged.

Tips & Warnings

 
Don't forget to include your head, if you use a type I Marine Sanitation Device; the macerator pump is electrically powered. Crystalline panels are rigid, but offer twice as much efficiency as thin film panels; however, thin film panels come in both rigid and flexible sizes, and capture light more efficiently on cloudy days.
 
Don't forget to include your head, if you use a type I Marine Sanitation Device; the macerator pump is electrically powered.
 
Crystalline panels are rigid, but offer twice as much efficiency as thin film panels; however, thin film panels come in both rigid and flexible sizes, and capture light more efficiently on cloudy days.
 
Check out the charging characteristics of a solar panel and its installation instructions carefully before making a purchase. While a solar panel is less boat-intrusive and more environmentally friendly than a generator, not all solar panels are created equally and will end up costing -- in terms of convenience and suitability -- more than others.
 
Check out the charging characteristics of a solar panel and its installation instructions carefully before making a purchase. While a solar panel is less boat-intrusive and more environmentally friendly than a generator, not all solar panels are created equally and will end up costing -- in terms of convenience and suitability -- more than others.

Article Written By Will Charpentier

Will Charpentier is a writer who specializes in boating and maritime subjects. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. He is also a certified marine technician and the author of a popular text on writing local history.

Don't Miss a Thing!

All our latest outdoor content delivered to your inbox once a week.

FREE UPDATES

Subscribe

We promise to keep your email address safe and secure.