How much solar power to sail the seas?

Most boats have two types of batteries. The starting one gives off a short burst of current to power the engine. The deep-cycle one or the house battery powers all the electric appliances when you are not connected to shore power or not using an alternator in the engine. But how do you keep it charged in your travels out in the open sea?

Whether you have a small boat or a fancy yacht, solar panels are a good choice. They aren't those loud and smelly generators: they don't need fuel, pay for themselves over the years and produce energy even when you're away from your ship. You don't need a solar farm to become energy independent: one solar panel may well be enough. Everything depends on your energy needs, though.

To determine how many panels you need, first you have to calculate your energy consumption. When it comes to a boat, the simplest way to do it is to make a table and include:

• all the electrical devices you plan to use during your trip;
  
• their power rating;
  
• number of hours in use per day.
  

It will give you an understanding of how much power your future solar array has to generate.

Let's try to compose this table together.

Thus we have to figure out how to get around 1 kWh of power with our solar array. Solar panels on your boat aren't going to perform at their maximum, so let's add 25% to our energy needs just to be safe.

1 kWh * 1.25 = 1.25 kWh

The number of peak sun hours, during which panels perform at their best, depends on the area where you're sailing at and the time of year. In the USA it ranges from 4 to 5 hours on average. Let's assume our array is going to give its all for 5 hours a day. Hourly power output of our marine solar panels should be:

1.25 kWh ÷ 5h = 250 W

As you can see, our sailors don't consume much, so we need only 250 W of solar power. 100 W is considered a very popular power size of solar panels for boats as well as for RVs. Three of those are going to be just enough. However, you might get one 300 W solar panel instead to save some space. Now let's talk about how we're going to install it.

When it comes to solar panel marine installation, space is the primary concern. This is why sailors come up with all sorts of ideas about where to put solar panels. They clip panels to a stern rail, attach them to the deck, install PV modules on canvas and even on sails.

Shading is a common problem with boat solar panel installation. The mast, the flag, the sails – anything can cast a shadow on your panels and greatly decrease their performance. This is why solar panels on boats are often connected in parallel: if one panel stops working, it doesn't affect the others.

Direction and angle are crucial for solar panel performance. In the USA panels generate maximum energy when they face south at 30-45 degree angle. However, a boat constantly moves around, so there is no catch-all solution. Just keep in mind that it is best to keep panels perpendicular to the sunlight.

To fix solar panels you can use the velcro tape, glue or fasteners. However, the method of installation depends on the type of panels you choose.

Rigid solar panels, monocrystalline or polycrystalline, are more efficient. It means they produce more energy while occupying less space. However, they are the most expensive among panels, heavy, and you'll probably need to use a drill to fix them.

Thin-film or amorphous solar panels are cheaper, but less efficient. Plus, their lifespan is shorter – from 10 to 15 years. The installation process is much simpler: they are usually fixed with strong adhesives. This type is flexible, so it's easier to install on boats with difficult configurations. Manufacturers claim that you can even step on these panels without the risk of breaking them, though we would recommend against it anyway.