Retrofitting solar panels (photovoltaic systems) on boats and yachts is a sensible measure for greater self-sufficiency on board—especially for sailors, long-distance crews, or owners who want to anchor in quiet bays for extended periods. However, there are some important technical, safety, and legal aspects that should be considered during installation.
Self-sufficient on board: To ensure that lights, refrigerators, electric outboard motors, and water pumps function reliably without a power connection, boat owners are increasingly turning to solar energy. “Installing a photovoltaic system on a vehicle is a practical solution for generating electricity independently and emission-free—provided it is installed professionally,” says Frank Schneider, vehicle technology consultant at the TÜV Association.
“In practice, experts repeatedly encounter adventurous homemade constructions that disregard basic safety requirements.” For example, inadequately secured or unprotected components can come loose or slip during braking maneuvers. Schneider: “Critical issues include incorrectly dimensioned cables, missing fuses, or thermal overload. In the worst case, this can lead to short circuits or fires.”
Retrofitting a photovoltaic system on board requires a great deal of technical expertise
What applies to motorhomes from the perspective of the TÜV professional also applies to boats and yachts. In both cases, a great deal of technical expertise is required, especially when retrofitting. Which cables can be used? How must modules be fastened or battery systems secured? Which installations and conversions are actually permitted? SeaHelp explains what must be taken into account when installing solar systems on boats/yachts.
Boat owners should proceed with caution when selecting components. There are two types of solar modules: flexible (lighter but more sensitive) and rigid (more robust but heavier). There are also differences in terms of charge controllers: an MPPT charge controller is more efficient than a PWM controller – especially in changing light conditions.
(Explanation of terms: Maximum Power Point (MPP) refers to the point at which a solar system achieves its maximum power output. This point is influenced by various factors, such as temperature changes or shadows cast by surrounding objects. Maximum Power Point Tracking (MPPT) makes it possible to achieve the maximum output of the solar system despite these influences by continuously searching for the optimal power point).
Care should be taken when selecting panels, charge controllers, batteries, cables, and connectors
What is the difference between MPPT and PWM? PWM (pulse width modulation) controllers reduce the voltage of the solar system to almost the battery voltage, while MPPT controllers optimize the input voltage to utilize the maximum power of the solar system. MPPT controllers are therefore more efficient than PWM controllers.
How does Maximum Power Point Tracking (MPPT) work? There are various technical methods for achieving the optimum power point, such as shadow management, voltage increase, load jumps, increasing conductance, and constant voltage. These methods enable a continuous search for the maximum power point, regardless of external conditions.
Once you have decided on the appropriate charge controller, you need to choose a battery: here you can choose between AGM, gel, or lithium batteries – depending on your requirements. AGM stands for Absorbent Glass Mat – a special design for lead-acid batteries. The difference to conventional starter batteries lies in the way the electrolyte is stored: instead of being free in liquid form, the acid is bound in a glass fiber mat. It should be noted that special fuses are required for lithium batteries.
With regard to cables and connectors, it should be noted that only UV-resistant, multi-core, marine-certified cables should be used (e.g., H07RN-F or special marine cables). Plugs should comply with the IP67/68 standard (the IP67 standard protects against dust and temporary submersion up to a depth of one meter for a maximum of 30 minutes, while the IP68 standard protects against dust and permanent submersion under conditions specified by the manufacturer, which is typically deeper than one meter).
The solar system must be installed professionally, otherwise there is a risk of fire
Finally, there are also a few things to consider during installation: it should be carried out “professionally.” This means: the modules must be mounted in such a way that they are shock and vibration resistant, preferably on solid structures (e.g., a equipment rack, davits, or a bimini frame). Adhesive or mounting solutions for flexible modules should only be carried out with suitable materials (e.g., Sikaflex 292i, UV-resistant).
When laying cables correctly, care should be taken to ensure that they are never loose; instead, the cables must be securely fixed in place with clamps, cable ducts, or UV-resistant cable ties. In addition, the cables should be protected against chafing (e.g., by cable glands, rubber grommets, etc.).
Furthermore, attention should be paid to the correct cable cross-sections, which depend on the current and cable length – keyword: voltage loss. When using fuses, they should be placed close to the battery (fuses according to ISO 10133 or ISO 13297 – depending on the on-board voltage system).
As far as electrical connections are concerned, the connections should only be made via marine-grade fuse panels. Open luster terminals should be avoided – only screw-connected, encapsulated terminal connections should be used. When installing in metal yachts, care should also be taken to ensure that a connection to the lightning protection or grounding system may be necessary.
Important: Improper wiring poses a fire hazard. Lithium batteries should only be used with a BMS (battery management system) and temperature sensors. And: missing fuses or incorrectly dimensioned cables are also common causes of fire!
Although there is no general TÜV certification for boats, improperly installed systems can still be relevant for insurance purposes in the event of damage
What is legally permissible – and what could be objected to? Although there is no general TÜV requirement in Germany and Austria, for example, as there is for cars, certain requirements still apply – e.g., if the boat is registered in the German maritime register or is used commercially (e.g., for charter). For recreational boats, modifications are subject to CE directives (Directive 2013/53/EU) and, if applicable, construction and equipment regulations.
Why should you always err on the side of caution in this case? On the one hand, there is the safety aspect: malfunctions or smoldering fires are not uncommon with poorly installed solar systems. Insurance coverage should not be neglected either: in the event of fire damage or a short circuit, the insurance company will check carefully whether everything on board has been installed in accordance with regulations.
Finally, a professionally installed system is likely to increase the resale value of the boat. Also worth considering: on international voyages, problems may arise during inspections by the authorities if the system has been installed incorrectly.
Tips for proper installation can also be found in a new information sheet from TÜV Germany
Tips for DIY enthusiasts who want to retrofit a photovoltaic system on board: Answers can also be found in the new information sheet 769 “Photovoltaic systems in/on vehicles,” which was recently published by the TÜV Association Germany and is expressly intended to assist with professional installation.
The information sheet is primarily aimed at experts who are responsible for individual assessments, change approvals, or vehicle inspections as part of the general inspection for motorhomes. However, it also contains detailed information that can help DIY enthusiasts to install PV systems professionally and safely on boats and yachts.
The main contents of the information sheet include: Electrical safety requirements, for example cable dimensioning, fuses, electromagnetic compatibility (EMC), specifications for the mechanical fastening of modules, energy storage devices, and controllers, information on grounding, fire protection, reflection behavior, and roof load, technical rules for cable protection, connection technology, and insulation monitoring, as well as references to relevant standards such as DIN VDE 0100-721, DIN EN 50618, and UN regulations. The information sheet is supplemented by information on cybersecurity, software updates, and testing principles for lithium batteries or high-voltage systems.
The new TÜV Association Information Sheet 769 “Photovoltaic Systems in/on Vehicles” is now available as a digital version in the TÜV Association online shop and costs €24.90: shop.tuev-verband.de/merkblaetter.
