Picking the best solar panels for a sailboat: Buyer’s guide

When it comes to solar panels for sailboats, their weight and size matters more than with PV modules for residential systems. Efficiency is important but power — not that much, because the energy needs of a boat are relatively low. The first thing you’ll have to decide about your panels is their type.

Generally, you’ll choose between thin-film panels and monocrystalline modules. While polycrystalline panels are still around and they are indeed cheaper than mono panels, they are much less efficient, which means they’ll need more space and add more weight to your boat.

Thin-film or flexible solar panels bend well and they are very easy to install which makes them a great choice for boats with difficult configurations. Some sailors say that flexible panels are the best choice for fast boats because they don’t impact the aerodynamics of a vessel as much as rigid panels do.

The downside of flexible panels is their low wattage. If there are many appliances on board, you’ll need several panels and you’ll need to find the right place for each of them. They also age faster than rigid panels — a thin-film panel generally lasts for 10-15 years.

Rigid solar modules, monocrystalline and polycrystalline, are heavier and bulkier than thin-film panels. You can fix flexible panels with adhesives, but rigid panels require drilling. They are also more expensive than flexible panels.

On the other hand, monocrystalline panels are the most efficient type of panels which means that they provide more power for less space. Even one powerful mono panel can be enough for everything that you’ve got on board. They are also much more reliable and will survive any storm that is coming your way. A monocrystalline panel lasts for at least 25 years.

The best solar panels for sailboats don’t have to be powerful, but they better be efficient — find the number in the datasheet. For rigid panels anything over 18-19% is fine. Panels also should be sturdy enough to withstand seastorms. You generally also want good shading tolerance since panels often get shaded by masts and sails. Finally, good performance in low-light conditions is appreciated.

Picking bifacial panels, 72/144-cell panels or larger, anything too powerful generally doesn't make a lot of sense. Performance at high temperatures matters less than it does with home systems. Warranties also play a lesser role. You won’t be able to make use of them because they generally have effect only for residential installations.

The markets of thin-film and rigid panels are different. Generally, a manufacturer of flexible panels doesn’t offer mono- or poly-panels. Canadian Solar, Q CELLS and Jinko Solar are good choices when it comes to monocrystalline modules for boats. Renogy, WindyNation and PowerFilm make fine thin-film panels.

The amount of power for your boat depends on the number of appliances on your board. There are two main ways to determine the size of installation that you need. You can take a test trip and see how much of your battery’s charge you’ve spent in one day. You can also do the calculations manually: write down all the appliances on the board with their power rating and number of hours in use per day. You can read about it in detail in our article "How much solar power to sail the seas?" It doesn’t make sense to oversize a marine PV system, because all the excess power will just go to waste.

Keep in mind that adding photovoltaics doesn’t make your vessel a solar boat, unless you have a solar-powered motor. You can switch your boat to solar energy fully, especially if it’s small, but you’ll have to calculate your energy needs accordingly.

Once you’ve purchased your panels, you’ll have to install them properly. You can order professional service or do it yourself. The most popular places for solar panels on a boat are a stern rail, masts, deck and canvas. Thin-film panels can even go on the sails. Ideally, you want a place where panels wouldn’t be shaded by masts on any other parts of a boat.

We’ve asked our engineer to pick the panels that would complement a small boat well. These are his choices:

Solar panels from ZNShine Solar are inexpensive and fit all kinds of applications, including boat systems. ZXM6-NH120-370/M provides 370 Watts of power with a 19.88% efficiency. It performs well in low-light conditions. Graphene coating increases power generation and allows self-cleaning. The only downside is a lower wind tolerance, compared to other models: it is rated to withstand 2400 Pa pressure which is comparable to 140 mph wind.

MSE 345 is a simple solar panel for all kinds of applications, including boat installations. Mission Solar panels are manufactured in Texas. The module provides 345 Watts of power with 18.7% efficiency. It is certified for high snow (5400 Pa) and wind loads (4000 Pa). The model is resistant to salt mist corrosion.

Suntech is a Chinese company that offers quality budget-friendly solar panels. The STP365S model stands out in line because of its great performance in weak light, such as cloudy weather and mornings. It is designed to withstand harsh weather conditions, and the module is certified to tolerate wind of over 170 mph. Half-cut design makes cells sturdier and improves shading tolerance. Overall, this panel earns a place among the best boat solar panels.