When planning a long cruise, the question of energy becomes central. How can you cover your onboard needs without being dependent on the engine or a noisy, power-hungry generator? Solar panels are proving to be a sustainable solution, suited to independent living. But with so many different models, boat configurations and needs to choose from, there's plenty of food for thought. This article answers them with pragmatism, insight and feedback.
Why install solar panels on large cruises?
Energy autonomy is a quest common to all long-distance sailors. Solar panels allow us to power essential systems (fridge, autopilot, lights, instruments, recharging appliances) without having to start the engine. It's also a way of respecting the places we pass through: silence on board, no exhaust fumes, no noise pollution in anchorages.
The advantage? A source of energy that's free once installed, requires no complex maintenance, and works just as well offshore as it does at port. For those planning to live aboard for several weeks or months at a time, it's an essential investment.
Evaluate your on-board electrical needs
Before choosing your system, you need to know your average daily consumption. A fridge, a watermaker, LED lighting, an autopilot for navigation, instrument and telephone recharging: all this added up can reach between 100 and 300 Ah/day.
There are a number of tools and spreadsheets available to help you make this calculation. It's best to leave a margin for days without sunshine, while remaining realistic about your usage. Your needs may change over time, so it's best to oversize slightly from the outset.
On average, a family on a long-distance cruise consumes between 80 and 150 Ah per day. For such autonomy, you'll need a solar system capable of producing around 500 to 800 Wp (peak watts) per day, i.e. between 3 and 5 panels depending on unit power.
What type of panel should I choose?
There are three main families: rigid (often gantry-mounted), flexible (glued to bimini, hood or deck) and semi-flexible removable.
Rigid panels generally offer better performance and longer service life, but require a fastening structure. Flexible panels, on the other hand, can be easily integrated without drilling, but wear out faster and heat up more. The choice depends on the space available, your budget and your sailing schedule.
Finally, when it comes to monocrystalline and polycrystalline panels, monocrystalline panels offer better performance in low-light conditions, which is an advantage at sea.
Where and how to install them?
The place of installation has a major influence on performance. A panel in the shade of a boom or sail quickly loses efficiency. The gantry remains the most effective solution, with good exposure and little risk of shading. The bimini, canopy top or even deck can be used, but with more compromises.
And don't forget panel ventilation: a panel that heats up too much will lose its efficiency. A tiltable installation further optimizes yield, but is more rare and restrictive when sailing.
Note: there are now bifacial solar panels, capable of capturing light from both sides. On a sailboat, this can be interesting if they are raised and exposed to reverberation (particularly in Polynesia or the West Indies). Their efficiency can be 5 to 15% higher, depending on the environment.
The right regulator and battery compatibility
An MPPT (Maximum Power Point Tracking) solar controller is often recommended to maximize yield. It adapts panel voltage to battery voltage. Conversely, a simpler but less expensive PWM (Pulse Width Modulation) regulator simply lowers the panel voltage to that of the batteries, resulting in a loss of efficiency.
Check that your batteries (AGM, gel, lithium) are compatible and correctly sized. A good solar installation is nothing without a suitable battery bank.
Quick comparison
- Rigid monocrystalline
Yield: 4/5
Cost (?/Wp): 1.2 to 2.5
Installation: arch or gantry
Durability: 5/5 - Flexible monocrystalline
Yield: 3/5
Cost (?/Wp): 2.5 to 4
Installation: Glued or fixed
Durability: 2/5 - Rigid bifacial
Yield: 5/5
Cost (?/Wp): 3 to 5
Installation: Arch over water
Durability: 4/5
Controllers :
- PWM
Efficiency: 2/5
Suggested retail price: ?30 to ?100
Recommended for : Small systems (less than 100 Wp) - MPTT
Yield: 4/5
Guide price: ?80 to ?300
Recommended for: Medium to large installations
Practical advice and feedback
- Clean the panels regularly: salt, droppings and dust reduce their performance.
- Avoid partial shading: a cell in shadow can affect the whole panel.
- Plan a simple monitoring system to track production and adjust your usage.
Many navigators install too few panels. When in doubt, plan ahead. We often think we've had enough... until the first extended anchorage on an overcast day.
Conclusion
Fitting solar panels is not just an optional extra for long-distance cruising: it's the key to greater comfort, autonomy and peace of mind. With a well-thought-out installation, you'll reduce your ecological footprint while gaining in freedom. And if you're unsure about sizing or products, it's best to seek advice: every boat is unique, and every crew has its own needs. That's part of the fun of roaming: learning to deal with the elements.
As Thomas Friedman reminds us:
"The sun doesn't send us a bill."
So we might as well make the most of it.
