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SolarTown Learning

Great Solar Solutions for Boating Enthusiasts

Category: RV and Marine

Many marine travelers are looking for ways to reduce their impact on the environment while saving money. Solar is a great way to accomplish both goals, and contrary to what you may assume, choosing solar for your marine expeditions doesn't have to be troublesome or expensive. Choosing a high-quality marine solar system that will suit both your maintenance and budget requirements is relatively simple with such a wide selection of marine solar products on the market today. Solar energy for boats

What Solar Can Bring to Your Marine Lifestyle

For the boater, there are many benefits to considering solar power. Most importantly, with solar you have fewer concerns about when you will find the next electrical outlet or whether you will run out of fuel to power your motor or generator. Solar provides a fuel-free, unplugged power source that helps you cut the ties to traditional energy resources.

Your solar system can also be tailored to fit your particular needs and budget, so you can become as energy independent as you like. Whether you want enough energy to power your stereo in the evening or if you want the ability to eliminate problems associated with dead batteries, there's a solar solution for you. Solar photovoltaic (PV) systems come in a wide variety of models, sizes, and capacities, with a ton of extra tools and gadgets for improving any solar arrangement's compatibility with your existing power system. And most solar energy systems can be expanded indefinitely, giving you the ability to add more solar power as time goes on.

Solar energy systems also come with two practical benefits: they run silently and they produce no heat while generating energy. Unlike noisy engines or generators, solar can be used to provide power without the disruption of these other fuel sources. And if the weather is particularly hot, solar won't add to your cooling challenges because it won't heat up your cabin like a diesel engine will.

Of course, solar also has the potential to reduce your boating costs by reducing or eliminating the need for traditional fuels. With correct installation and sizing and attention to optimum solar collection, you may be able to offset a significant portion of your boat's operating costs with solar.

Here are a few examples of solar in marine applications:

  • All batteries self-discharge, and keeping them topped up can be a challenge for some boat owners. In smaller boats, solar can be used to keep batteries fully charged when sitting at her slip or on a trailer to avoid the problem of dead batteries.
  • Larger boats can also benefit from solar, using it for charging batteries or as a power source when mooring without shore power. Solar boat panels generally generate pure DC charge, making them very compatible for most boats provided there is a regulator in the circuit.
  • Cruising and racing sailboats can also benefit from solar. Using PV panels, boaters can generate energy freely to augment or replace other charging sources on board.

Solar can go hand-in-hand with a great boating experience. But how do you go about choosing a system that's right for your unique situation? Read on for some great advice when choosing solar for your marine application.

Calculating Your Marine Solar System's Size

Determining how much energy you consume, and then using that information to estimate how large your solar marine system should be (depending on how much energy you'd like to offset), is the first step in choosing a solar PV system for your boat. All solar panels are measured in terms of Watts, Amps, or both, but for our purposes, we'll talk in terms of amp-hours (Ah) for simplicity.

By and large, most boaters have an idea of how much energy in terms of amp-hours that they use in an average day while cruising; many also know the total Ah capacity of their batteries. If you are not clear about how much energy your boat uses daily, you can calculate that number by taking the Ah rating of your various devices and multiplying those by the number of hours they are used on average. Here's an example:

  • Autopilot runs for 15 hours/day and uses .25 amps = 4.8 Ah/day
  • VHF radio is on 12 hours/day at .6 amps - 7.2 Ah/day
  • Interior light on for 2 hours/day at 1.1 amp = 2.2 Ah/day
  • Running light is on for 9 hours/day .8 amps = 7.2 Ah/day


  • This equals 21.4 Ah/day

You can complete a similar evaluation of your power consumption by adding up the energy use from each of your on-board devices in a similar manner. Using this number, we'll determine what size you will need for your energy requirements (assuming you want to generate 100% of your power via solar).

There are two shortcut assumptions we make when calculating the size of a marine solar system:

  • Maximum daily solar output: Although many factors will determine the efficiency of your PV system-battery size, age and composition of the battery and panels, shading and other obstructions, speed of self-discharge, as well as your position on the globe-we'll use a standard average to calculate how much energy a solar panel will gather in a day: 5 hours/day = the maximum time a PV panel will generate energy.
  • Battery size maintained by a given solar system: In general, a PV system can maintain a battery that's about half the size of the output capacity. So a 150 mAh solar panel should be able to maintain a 75 Ah battery.

In our example, we require 21.4 Ah/day of energy. Multiplying this amount by two to determine the size of solar panel required, we can estimate that we need a marine solar system that will produce upwards of 40 Ah of energy daily. Since portable solar panels suitable for marine applications range in size from 150 mAh to 1,700 mAh, to generate 100% of our energy using solar, we'd need approximately one 150 mAh solar panels. If these calculations seem too complex, you can also use an Ah meter to do the calculations for you.

Solar Panel Types and Solar Add-Ons

Just like solar PV for your home, solar panels used in marine applications come in two general types: crystalline and thin film. Crystalline panels are by far more efficient than thin film models, with monocrystalline panels producing the most power per square foot than any other type. Polycrystalline panels are somewhat less expensive than monocrystalline panels, but because of their lower efficiency, you'll need more of them to get the job done.

Thin film solar panels are the least efficient option, but what they lack in efficiency is often made up by their flexibility for many boaters. Thin film panels come in both foldable and flexible panels and can be laid out or wrapped around a variety of structures on your boat using bungee cords, grommets, or other fasteners (just be sure they're tethered down when you're under way or in windy weather).

But solar panel type isn't the only question you'll need to answer when selecting a system for your boat. Here are a number of additional features and add-ons you should be mindful of when choosing a solar electric system for your boat:

  • Trickle charger: Because most rechargeable batteries will lose their charge gradually over time, a trickle charger is almost essential. This add-on will ensure that your battery's power is replenished at the same rate as it self-discharges, resulting in a battery at full capacity at all times so that you can avoid dead batteries.
  • Solar regulator: If you're concerned about overcharging your battery, adding a solar regulator is good insurance. These small devices will ensure that your solar panel charges your battery only to capacity and no further and are ideal for times when you can't be present to monitor your electrical system.
  • Mounts and connectors: Today, there are numerous ways to connect your solar panels to your boat. Ask yourself: are you a "set it and forget it" type? If so, you want a permanent installation that involves fastening your panels securely to your boat. On the other hand, if you are willing to invest time to adjust the position of your panel for maximum solar collection, then you may want to consider less-permanent installation methods. These include adjustable rigging options such bungee cords, clamps, rail mounts, and telescoping mounts that allow you to move the panel throughout the day.
  • Tools for integration into your boat's electrical system: If you'd like to tie your solar panels into your boat's electrical system, you generally have two options. For a temporary solution, you can run duplex wire down into your boat and plug it into a DC outlet or use a polarized plug to connect it your electrical system. A more permanent solution involves duplex wire and a waterproof deck connection that's connected to a dedicated circuit breaker on the DC distribution panel, which allows you to switch the solar system on and off as needed.

If you've got questions about your solar options, give SolarTown a call and we'll talk you through all of your choices.

Installing Your Marine Solar System for Maximum Power Generation

Where you locate your solar panels on your boat is perhaps one of the most important steps to renewable energy success in marine life. There are numerous obstructions that can diminish the capacity of your solar system-booms, the mast, running rigging, and more. Even a slight shadow over your panel will reduce your panel's efficiency dramatically, so choosing an ideal location is paramount.

The key is to place your panel where it can collect solar energy unobstructed for at least 5 hours every day. This will sometimes require creative solutions for locating your solar panels, since the most logical places-the top of a cabin or on a boat's dodger-will present many obstructions.

Another important principle to remember is that the solar panel should be perpendicular to the sun's rays as much as possible. This may require that you adjust the panel to track the sun throughout the day, but this method will result in a greater degree of energy independence. Nevertheless, you don't have to completely fuel-free. Even reducing your energy consumption slightly will greatly cut the duration and frequency of engine use.

With these tips, we know that you will enjoy your marine solar system.