Finding Your Perfect Off-Grid Power Partner
Choosing the right solar panel for a campervan, motorhome, or caravan is a decision that extends far beyond simply selecting a wattage, although wattage is an important consideration. The panel must be a seamless partner to the vehicle, fitting securely and discreetly while providing a reliable source of power. This guide is designed to aid your selection process by matching specific solar panel types to the unique characteristics of different recreational vehicle roofs.
At Solar Technology, we offer four distinct solar panel styles: The Rigid Mono High Density (MHD) glass panel, the lightweight Rigid SlimEdge panels, and the two semi-flexible options, the Flexi MHD and the Flexi standard. We have analysed the optimal application of each panel type across four common vehicle roof configurations - a campervan with a slightly curved metal roof with ridges, a VW campervan with a curved fibreglass pop-top roof, a motorhome with a flat floating metal roof, and a caravan with a curved aluminium roof.
Executive Summary: Your Quick-Reference Panel Picker
The selection of a solar panel is a direct function of the vehicle's roof type and the user's priorities regarding aesthetics, durability, and installation. While all panels convert sunlight into electricity, their physical attributes dictate their ideal application. The following table provides a high-level summary of the best panel for each specific roof configuration, with detailed explanations provided in the sections that follow.
Understanding the Panels
The range of solar panels for recreational vehicles offers a solution for nearly every need, with each type distinguished by its construction, materials, and physical properties. Understanding these differences is the first step toward making an informed decision.
The Rigid Panels: Powerhouses in a Frame
Rigid solar panels are the traditional choice for mobile power systems, known for their robust construction and proven durability.
Rigid MHD (Aluminium Frame & Glass)
The Rigid Mono High Density (MHD) solar panel represents the zenith of conventional solar panel design. It is a formidable unit built around a sturdy, anodised aluminium frame and protected by a durable glass panel. The core of its performance lies in the innovative shingled monocrystalline solar cells, which are designed to deliver superior efficiency in a smaller footprint compared to older technologies. This allows the panel to generate a significant amount of power per day—for example, a 100W panel can produce up to 600W per day, providing ample energy for off-grid travel.
Despite its power output, its physical dimensions and weight are critical considerations. A 100W Rigid MHD panel measures 1150x460x35mm and weighs 6.9 kilograms, making it the heaviest and thickest option in the line-up. This weight and bulk necessitate a secure, elevated installation using brackets, which is a key factor in its ideal application. Solar Technology backs the panel’s longevity with a robust 10-year module warranty, reflecting a high degree of confidence in its glass and aluminium construction.
SlimEdge Rigid (Aluminium Frame & 5-layer composite panel)
The SlimEdge rigid panel is a modern evolution of the traditional rigid panel, designed to address the challenges of weight and profile. It is a superior option for users who want the durability of a framed panel but require a lighter, less bulky solution. The primary material difference is the replacement of the glass top sheet with a tough, lightweight 5-layer composite panel. This material choice is significant, as it allows the panel to be up to 50% lighter than conventional rigid panels and gives it an ultra-thin 12mm profile.
Like its MHD counterpart, the SlimEdge utilises high efficiency shingled monocrystalline cells and is built with a sturdy anodised aluminium frame. This combination of advanced materials and cell technology provides a strong, aesthetically pleasing panel that retains the long-term durability expected of a framed unit. It also carries a 10-year panel warranty, demonstrating that the shift from a glass top sheet to a composite panel does not compromise the panel's long-term integrity.
The Material and Warranty Trade-off
The choice between the Rigid MHD and the SlimEdge rigid panel highlights a crucial design consideration. The Rigid MHD panel's glass top sheet is a heavy, time-tested material that provides excellent resistance to scratching and impact. In contrast, the SlimEdge's composite panel is a highly durable construction that offers a significant weight reduction and a lower profile. Both panels are engineered with strong aluminium frames and high-efficiency cells, and crucially, both are backed by the same 10-year warranty.
This equal warranty period suggests that, for general use, both material choices are considered to have a comparable lifespan. The decision is therefore not a matter of durability but a direct trade-off between weight and profile. A user concerned about minimising the load on a vehicle's roof or seeking a more discreet installation would gravitate towards the SlimEdge. In contrast, a user who prioritises the time-honoured durability of a glass panel would choose the Rigid MHD.
The Flexible Panels: Lightweight and Adaptable
Flexible panels, often called semi-flexible, are engineered for situations where a lightweight, low-profile, and contour-hugging solution is paramount, though there is a premium for flexibility.
Flexi MHD
The Flexible MHD solar panel combines the best of both worlds: the advanced cell technology of the MHD line with the adaptable nature of a flexible panel. At a mere 2mm thick and weighing only 1.9 kilograms for a 110W model, it is an ultra-lightweight and discreet option. Its top sheet is a tough ETFE material, specifically tested for resistance to extreme conditions such as saltwater spray and ultraviolet (UV) light.
This panel is designed for flat roofs as well as surfaces with "a slight curve," making it a perfect choice for campervans and boat decks. However, the physical flexibility and material choice are reflected in a shorter module warranty of 4 years.
Flexi Standard
The Flexible Standard panel is the classic semi-flexible option, known for its versatility and resilience. Its design features a durable, six-layer laminate with an ETFE top layer, providing extra toughness under challenging conditions. These panels are 4mm thick and are also rated for use on flat or slightly curved surfaces.
A key engineering feature of the Flexi Standard panel is the inclusion of built-in shading diodes, which are housed within the waterproof junction box. These diodes are designed to help prevent damaging "hot spots" that can occur when a panel is partially shaded, a common scenario on campervans and boats. Like the Flexi MHD, its durability is reflected in a more limited 2-year panel warranty.
Warranty and Practical Durability
The difference in warranty periods between rigid (10 years) and flexible (2-4 years) panels is a critical indicator of their expected long-term performance. While a flexible panel is rugged and tested for UV and salt spray resistance, its construction lacks the structural integrity and resistance to impact provided by a rigid panel's glass and aluminium frame. Flexible panels are more susceptible to damage from a direct impact, such as falling branches or walking on the surface.
Therefore, the choice is between two forms of durability. The rigid panel is a robust, long-term power solution that can withstand physical stress and impact. In contrast, the flexible panel offers a different form of durability—a resilience to bending and a low profile that makes it less susceptible to wind damage. This understanding is crucial for a customer to weigh the benefits of a lightweight, discreet installation against the long-term structural integrity and warranty of a rigid panel.
Matching Panels to Your Vehicle Roof
The ideal solar panel for a vehicle is one that is perfectly suited to its roof's specific shape, material, and any functional considerations.
The Campervan with a Curved Metal Roof with Ridges
A campervan with a curved metal roof and ridges presents a specific set of challenges for solar panel installation. The gentle curve and the presence of raised structural ridges make a traditional flat, rigid panel a poor fit. Attempting to mount a rigid panel directly on the roof would cause it to "high-centre" on the curve, leaving significant air gaps at the edges and creating a non-uniform surface. To achieve a secure fit, a complex framework of custom brackets would be required to clear the ridges and create a flat mounting surface. This elevated structure, however, introduces a new problem: it creates a large windbreak and a space for air to get underneath, increasing aerodynamic drag and making the vehicle less stable in high winds.
The most effective and straightforward solution for this roof type is a flexible panel, either a Flexi MHD or a Flexi Standard. These panels are specifically engineered for use on surfaces with a slight curve, as they can contour to the shape of the roof. The preferred installation method is direct bonding with a strong elastic adhesive. This technique avoids the need to drill into the metal roof, preserving its integrity and preventing potential rust or leaks. It also results in an incredibly low-profile installation that sits flush with the roof, minimising wind load and maintaining the vehicle's original aerodynamics. To prevent heat build-up, it is critical to apply the adhesive in a specific pattern that allows for a small amount of airflow underneath the panel, as detailed in the installation instructions.
The VW Campervan (or similar) with a Fibreglass Pop-top Roof
The fibreglass pop-top roof on a campervan poses a unique challenge for solar panel installation. The roof's primary function is to be raised and lowered, and it is designed to be lightweight to avoid straining the lifting mechanism.
For this application, a flexible panel is the definitive recommendation. The ultra-lightweight Flexi MHD, at just 1.9 kilograms for a 110W panel, is an ideal choice as it adds minimal weight and will not strain the pop-top's lifting frame. The most secure and recommended installation method is bonding the panel directly to the fibreglass surface with a strong elastic adhesive. A further advantage of a flexible panel is its low profile, which ensures the panel remains a sleek, integrated part of the roof's design, avoiding any snags or issues when the roof is lowered. Some flexible panels also feature a rear-exit junction box, which allows for a completely flush installation without any visible cables or trip hazards.
If the pop-top roof is flat and without any ridges, then a second choice for consideration would be the SlimEdge range of panels. These are lightweight 5-layer composite panels, which, although heavier than the Flexi MHD panels, with the 100W and 120W SlimEdge panels being 3.7 and 4.2 kilograms respectively, are still light enough to be a consideration in this category.
As the lightest 100W MHD rigid panel with mounting brackets is 7 kilograms, fitting a rigid panel on a pop-top is not recommended. The weight could place an unnecessary strain on the lifting system or require an additional locking mechanism to prevent the roof from lowering under the weight.
The Caravan/Motorhome with a Flat Floating Metal Roof
Unlike a curved campervan roof, the main installation challenge is not the roof's shape but the lack of a stable, solid surface, as floating roofs move and flex with temperature changes.
The optimal solution for this type of roof is a rigid panel, either the Rigid MHD or the SlimEdge. The primary reason for this recommendation is that rigid panels are designed to be mounted on brackets, still allowing for the roof to move and flex.
Using flexible solar panels on this type of roof is not advisable. Since these panels are bonded directly to the roof, they would be subjected to constant flexing due to the roof's expansion and contraction. Flexible panels are primarily designed for curved surfaces, where they are gently shaped to fit the roof, and the flexing occurs only once during installation. Continuous bending of these panels will damage the crystalline solar cells, leading to premature panel failure.
The Caravan with a Curved Aluminium Roof
A caravan with a curved aluminium roof shares many of the same installation challenges as a curved campervan roof. The primary consideration is the roof's curvature, which makes a traditional flat, rigid panel a difficult fit.
For this application, there are two viable paths, each catering to a different set of priorities.
The most effective and straightforward choice for ease of installation, low profile, and weight is a flexible panel. The ability of a flexible panel to conform to the gentle curve of the aluminium roof allows for a clean, bonded installation that requires no complex brackets. This method preserves the roof's integrity, is aesthetically pleasing, and minimises wind resistance.
However, for a customer who prioritises the durability and long-term warranty of a rigid panel, a professional installation using specialised or custom-made brackets is a viable alternative. These brackets can be designed to compensate for the roof's curve, creating a level mounting surface for the panel. While this approach adds complexity, cost, and installation time, it provides the benefit of a 10-year warranty and a more structurally robust system.
The Motorhome with a Flat Solid Roof
A motorhome with a flat, solid roof provides the widest range of options, though the simplest and most cost-effective solution for this type of roof would be either the Rigid MHD or the SlimEdge panel. The primary reason for this recommendation is that the rigid panels offer the longest warranty for the lowest price, compared to the flexible panels. If there is no requirement for a panel to curve, then paying for the benefit of that flexibility is counterproductive.
An additional benefit of a raised installation is the improved cooling airflow underneath the panels, which enhances their power output. Furthermore, research suggests that smaller rigid panels (e.g., 100W) may have less flex and prove more durable over time for in-motion use on vehicles, compared to larger panels.
Comprehensive Comparison and Practical Advice
Choosing a solar panel is a matter of weighing key attributes against the specific needs of a vehicle and its owner. The final decision rests on a comprehensive understanding of each panel's strengths and weaknesses.
Key Factors for Your Decision
● Efficiency & Performance: All but the standard flexi panels are built with high-efficiency monocrystalline cells, ensuring excellent power generation. However, a panel's output is heavily influenced by its installation. A flat-mounted panel, even on a slightly curved roof, will perform well for most uses and avoid the maintenance issues associated with pooling water. Rigid panels, when mounted on adjustable brackets on a canalboat for example, can be tilted to an optimal angle to the sun, which can maximise energy output, particularly in low-light conditions or specific seasons.
● Durability & Warranty: The 10-year warranty on the rigid panels is a testament to the long-term confidence in their glass and aluminium construction. Glass is highly resistant to scratching, a significant advantage on a vehicle roof where branches and debris may be a concern. The shorter warranties on flexible panels reflect the reality that while their ETFE top layer is resilient to UV and saltwater, it is not as resistant to impacts as a glass panel.
● Weight & Aesthetics: Weight is a critical factor for any vehicle. A flexible panel's minimal weight reduces its impact on a vehicle's centre of gravity and fuel efficiency. The low-profile, bonded installation of a flexible panel also offers a clean, discreet aesthetic that integrates seamlessly with the roof's design. In contrast, a rigid panel, mounted on brackets, is a more visible addition that stands proud of the roof's surface.
● Installation Method: The installation method is a direct consequence of the panel type. Rigid panels require brackets to be securely attached to a vehicle with elastic adhesive, whereas flexible panels are bonded directly to the roof.
Panel-by-Panel Comparison Table
This table provides a concise, side-by-side comparison of the core attributes of each panel type.
Conclusion: Making the Right Choice with Confidence
The selection of a solar panel for a mobile power system is not a one-size-fits-all decision. The optimal choice is the one that achieves a perfect synergy between the panel's physical characteristics and the vehicle's unique roof.
For a customer with a curved campervan or a VW pop-top, the benefits of a flexible panel - its minimal weight, low-profile aesthetics, and adhesive-based installation are overwhelming. The Flexi MHD stands out as a premium choice with its high-efficiency cells and enhanced durability, while the Flexi Standard offers a versatile and cost-effective solution.
For a customer with a flat motorhome roof, a rigid panel is the most logical choice. Its ability to be secured using brackets while maintaining the best performance-to-cost ratio means it outclasses a flexible panel in this sector. The SlimEdge offers a lighter-weight solution, while the Rigid MHD provides a robust, heavy-duty alternative.
Ultimately, the decision comes down to a clear understanding of personal priorities. Whether a customer values the lightweight, discreet aesthetics of a flexible panel or the long-term structural durability and versatility of a rigid panel, an informed choice can be made with confidence.
We hope this guide has been helpful, if you need any further information, or would like to discuss your specific needs in detail, please contact our Technical Team by emailing support@solartechnology.co.uk