Sailboat Solar Panels: Your Complete Guide to Offshore Power

In a Nutshell...

Looking to go off-grid on your boat? Installing marine solar panels is the perfect solution. They're a reliable and eco-friendly way to keep all your onboard electronics humming, from the fridge to the navigation gear. This guide walks you through everything you need to know, from sizing your system to picking the latest tech. By understanding your energy needs and choosing the right setup, you can enjoy limitless power and a quieter, greener time on the water.

The gantry on this Jeanneau Sun Odyssey is an ideal location for solar panels, as there is nothing else up there to cast shadows over them.

Atop the gantry is a popular location for rigid solar panels...

Assessing Your Energy Needs
Factors Affecting the Performance of Marine Solar Panels
The Technology & Design of a Marine Solar Panel
Installation Considerations
Integrating with Your Existing System
The Cost of Going Solar
What Can Go Wrong: Troubleshooting Common Issues
Maintenance & Longevity
Summing Up
Frequently Asked Questions

Modern sailboats are packed with gadgets and gizmos that need electricity. From navigation systems and autopilots to fridges and entertainment systems, all that tech requires a reliable and sustainable energy source. Installing marine solar panels on your sailboat isn't just a smart move for keeping everything powered up; it's also a step toward eco-friendly sailing.

Assessing Your Energy Needs

Before you jump into installing solar panels, you need to know how much power your boat actually uses. Think of it like a budget: you can't manage your money until you know where it's all going.

Start by making a list of every electrical device on board—think GPS, lights, fridge, radio, everything. Then, estimate how many watt-hours each device consumes per day. Adding up these numbers gives you a solid idea of your total daily energy consumption. For example, my own old-school fridge on my wood-epoxy 38-footer chews through a hefty amount of power, so I know that’s my biggest draw and the key target for any solar setup.

Also, pay attention to when you use the most power. Are evenings when you have all the lights and electronics on? Knowing your peak usage times helps ensure your solar setup can handle your needs without any surprises.

Now, let's talk about cutting down on energy use. Switching to LED lighting is a simple way to reduce power consumption—they use less energy and last longer. Opting for energy-efficient appliances designed for marine use can make a big difference, too. And developing habits like turning off devices when they're not in use can help lower your overall energy needs. The less power you use, the smaller (and more cost-effective) your solar system can be.

Factors Affecting the Performance of Marine Solar Panels

The performance of your marine solar panels is pretty much all about one thing: the sun. Here’s how its behaviour, and a few other things, can impact your power output.

Angle of incidence of the sun's rays: This of course depends on season and latitude. At the equator the sun is high in the sky for much of the day, so excellent performance can be expected. In high latitudes, with the sun low in the sky, performance will be much reduced.

Period of exposure: At the equator, cloud cover accepted, you can feel entitled to 12 hours of sunlight. At high latitudes in the summer, rather more but less intense. But in these latitudes in the winter, you shouldn't expect much from your solar panels at all.

Temperature: As temperature rises, output falls. Output is normally quoted at 25°C, and in the sun-drenched tropics, their surface temperature could easily be double that. Were it not for the cooling trade winds, their output would be seriously impaired.

Cloud cover: Less is best. No surprises there, but modern panels no longer need bucketfuls of direct sunlight.

The Solar Panels on this HR 42 are mounted on the stainless-steel cockpit guardrail, and can be adjusted to get the best angle of incidence.

At anchor, these guardrail-mounted hinged panels can be angled towards the sun for maximum output.

The Technology & Design of a Marine Solar Panel

A photovoltaic (PV) solar cell consists of two layers of silicon-based laminates constructed as a 'semiconductor,' in which one of the layers is electrically positive and the other negative. When subjected to the sun's rays, the photovoltaic activity between the two produces an electrical current.

The principle isn't new, having been unearthed by the French scientist Henri Becquerel back in the 19th century, but it's all moved on a bit since then. So, if you're thinking about installing or upgrading your existing solar panels with the latest technology, here's what you need to be thinking about.

Advancements in Solar Panel Technology

Solar tech has come a long way, and there are some exciting advancements that are perfect for sailboats.

High-Efficiency Solar Cells:

Monocrystalline Panels: These are made from pure silicon, making them super efficient and space-saving—a big plus when deck space is limited. Plus, they have a sleek, uniform look that can complement your boat's style.

PERC Technology (Passivated Emitter Rear Cell): Panels with PERC tech have an extra layer that reflects unused sunlight back into the cell, boosting efficiency. This is especially handy on cloudy days or during sunrise and sunset.

Heterojunction (HJT) Cells: These combine different types of silicon to perform better in hot temperatures, making them ideal if you sail in warmer climates.

Flexible and Semi-Flexible Panels: Flexible panels can bend to fit the curves of your deck or bimini top. They're lightweight and durable, designed to handle the vibrations and movements of a boat. Plus, you can attach them directly to surfaces without heavy mounting equipment.

Bifacial Solar Panels: These panels absorb light from both the front and back, increasing the total energy they generate by up to 30%. If you mount them over reflective surfaces—like the water or a light-coloured deck—they can capture even more sunlight.

Innovations in Solar Panel Design

Sailing presents unique challenges, but modern solar panels are up to the task.

Marine-Grade Durability: Panels are built with materials that resist saltwater corrosion and UV damage. They have reinforced frames and special coatings to withstand harsh sea conditions.

Integrated Solar Solutions:

Solar Cloth & Sail Integration: Imagine solar cells embedded right into your sails or canvas covers. This setup uses space efficiently without changing your boat's appearance.

Deck-Embedded Panels: These panels sit flush with your deck, maintaining functionality and safety. Some even have textured surfaces to prevent slipping.

Lightweight Materials: Using advanced composites reduces the weight of the panels, lowering your boat's centre of gravity. This can enhance stability and even improve performance. As a sailor who has spent a lot of time calculating weight distribution and its effect on a boat's motion, I can tell you that every kilo counts, especially up high.

Installation Considerations

The skipper of this Catalina Morgan 43 has chosen the dinghy davits as the location for a couple of rigid solar panels

Another good location for solar panels is the dinghy davits

Proper installation is key to getting the most out of your solar panels.

Optimal Placement

Consider where the sun hits your boat throughout the day and avoid areas shaded by masts or sails. Tools or professional consultations can help you figure out the best spots for your panels.

Mounting Solutions

Fixed Mounts: Simple and sturdy, these mounts have no moving parts and can handle rough weather.

Adjustable Mounts: These allow you to tilt or rotate the panels to follow the sun, increasing energy capture—especially useful if you can adjust them based on the season or your location.

Electrical Infrastructure

Use marine-grade, tinned copper wiring to resist corrosion. Proper cable sizing prevents energy loss and overheating. And don't forget MPPT (Maximum Power Point Tracking) charge controllers—they optimise the energy you get from your panels. Unless you're an experienced electrician, it's a good idea to hire a certified marine professional to handle the installation. They'll ensure everything complies with safety standards.

This Pearson 590 has its solar panels mounted over the bimini

Whereas in this location, solar panel performance will be reduced by shadows from the mast and boom

F;exible polar panels on this J40 are mounted on its fabric bimini.

Flexible solar panels on a fabric bimini is an effective use of this space, but their output will suffer from shading on some points of sail.

Integrating with Your Existing System

A sailboat's electrical system is a complex network of components. Your new solar setup won't be working alone; it needs to play nicely with your alternator, shore power charger, and potentially a wind generator. This is where the right charge controller becomes crucial. It acts as a manager, ensuring that power from all sources is directed efficiently to your batteries without overcharging them. When you're tied up in a marina, your shore power might take priority, but as soon as you cast off, your solar panels should seamlessly kick in to top up the batteries. A multi-input charge controller or a dedicated wiring plan for each charging source is key to a robust and reliable system. To get a complete understanding of how all these parts work together, and to avoid common pitfalls, it’s worth diving deeper into a full guide to 12V electrical systems.

The Cost of Going Solar

The initial investment in marine solar panels can vary widely, but it's a cost that often pays for itself over time by reducing the need to run your engine to charge batteries or to pay for shore power.

Component	Price Range (UK)	Notes
Solar Panels	£150 - £600 per panel	Flexible panels are more expensive per watt than rigid ones.
MPPT Charge Controller	£100 - £500+	The price depends on the amperage & features (e.g., Bluetooth monitoring).
LiFePO₄ Batteries	£1,000 - £3,000+	A significant investment but offers a much longer lifespan & faster charging.
Wiring & Fuses	£50 - £200+	Marine-grade, tinned copper wiring is a must to resist corrosion.
Installation	£500 - £2,000+	Varies widely based on the complexity of the job.

What Can Go Wrong: Troubleshooting Common Issues

Even a well-designed solar system can have an off day. Knowing how to troubleshoot common problems can save you a lot of frustration, especially when you're far from land.

Low Power Output: If you notice a sudden drop in power, the first thing to check is shading. A partially shaded panel can drastically reduce the output of the entire array. Also, check for dirt, salt buildup, or bird droppings on the panel's surface. A quick rinse with fresh water might be all you need.

Battery Not Charging: Check all connections. Loose or corroded terminals are a common culprit for poor performance. Ensure the fuses on the system are intact.

System Overheating: This is less common but can occur with poor ventilation around the charge controller, especially on a hot day in the tropics. Make sure your charge controller is installed in a well-ventilated area.

On the Water...

We were around a couple of hundred miles west of the Cabo Verdes, on passage to the West Indies, when this chap came to join us. He's a Brown Booby and he stayed with us until Guadeloupe was smudge on the horizon. "Fascinating, but what's this got to do with solar panels?" I hear you say.

Well 'Bird', as he became known, took rather a fancy to them—particularly so as a location for his ablutions. I was well aware of the mess seagulls can make, but this was on another scale. Let's just say that he, if he was a he, was solely responsible for a considerable drop in our solar panel output.

"Bird", the uninvited guest that stayed with us most of the way across the Atlantic

Incidentally, if you'd like to hear more of Bird's exploits, take a look at Mary's eBook "First Time Atlantic Crossing".

Maintenance & Longevity

Keeping your solar panels in good shape doesn't have to be tough.

Routine Task	Frequency	Purpose
Cleaning	Regularly, as needed	Rinse panels with fresh water to remove salt & grime. Use a soft cloth to avoid scratching.
Inspections	At least once a month	Check for cracks, scratches, or loose connections. Look for corrosion on the wiring.
Protective Measures	When boat is not in use	Use covers for long periods of lay-up. Consider UV-resistant coatings.
Performance Monitoring	Regularly	Keep an eye on energy production. A sudden drop could signal a problem.

Summing Up

Adding solar panels to your sailboat is a smart move that boosts your independence on the water and reduces your environmental impact. By understanding your energy needs, embracing the latest solar technologies, and planning for future upgrades, you're setting yourself up for smooth sailing ahead. It's about more than just power; it's about the freedom to explore anchorages and cruise remote areas without worrying about running out of juice.

This article was written by Dick McClary, RYA Yachtmaster and author of 'Offshore Sailing' published by the Royal Yachting Association ( RYA) and member of The Yachting Journalists Association (YJA).

Frequently Asked Questions

1. How do marine solar panels work?

Marine solar panels, or photovoltaic (PV) cells, convert sunlight into electricity. They're made of semiconductor materials, usually silicon, which absorb photons from the sun. This creates a flow of electrons that generates a direct electrical current, which can then be used to charge your boat's batteries or power devices.

2. Are flexible solar panels as efficient as rigid ones?

Generally, rigid panels (often made with monocrystalline cells) are more efficient than flexible ones on a per-square-metre basis. However, flexible panels have a huge advantage in their ability to conform to curved surfaces and their lighter weight, making them ideal for mounting on dodgers, biminis, or decks where rigid panels might not fit.

3. How much power do I need from my solar system?

The power you need depends entirely on your daily energy consumption. A good starting point is to create a list of all your electrical devices and their average usage per day. This calculation, measured in amp-hours or watt-hours, will tell you the minimum output your solar system needs to provide to keep up with your demand.

4. What's the difference between a PWM and an MPPT charge controller?

A PWM (Pulse Width Modulation) controller is a simpler, more affordable option that regulates voltage by switching the current on and off. An MPPT (Maximum Power Point Tracking) controller is more advanced; it optimises the voltage and current from the panels to get the maximum possible power out of them. MPPT controllers are more efficient, especially in colder or low-light conditions, and can harvest up to 30% more power than a PWM.

5. How do I prevent my solar panels from being damaged by saltwater?

The best way to protect your panels is by choosing marine-grade products specifically designed to resist saltwater corrosion. Regular maintenance is also key: a simple rinse with fresh water after each trip or a strong sea breeze is the best way to remove salt deposits and prevent long-term damage.

6. If I have an array of solar panels on my sailboat that produce more power than I can use, can this damage my batteries?

The short answer is: no, not if your system is properly regulated.

You’ll want to ensure your system includes a quality solar charge controller:

PWM (Pulse Width Modulation): Basic, affordable, but less efficient
MPPT (Maximum Power Point Tracking): More expensive, but optimizes panel output and protects batteries better.