Everything you need to know about flexible solar panels
If you’re a boater, camper, or anybody who needs portable off-grid power, flexible solar panels are a great way to keep your devices powered with clean energy.
All of us are packing more and more energy-hungry devices with us all the time. Smartphones, tablets, cameras - indispensible little things that we need to keep charged all the time.
If you’re into outdoor activities or anything that takes you off the grid, keeping your devices charged starts to be a challenge if you’re away from a power outlet for a day or more.
If you only need a little power, portable batteries are good for a few charges of small devices. If you have bigger power needs and vehicle to carry it, you could fire up a gas generator. But do you really want that kind of noise while you’re out in the woods, trying to enjoy a little quiet?
If you plan to be off the grid for days or even weeks but don’t want the noise and maintenance issues of a generator, go with solar panels. Solar electricity is the ticket if you electricity without the smoke and noise. Batteries even come in sizes large enough to take the place of a gas generator.
The kind of solar panel we’re talking about is not the type you’d put on a house - too bulky, heavy, and not exactly portable. You want something lightweight. This is what flexible solar panels are for.
TIP: If it isn’t absolutely necessary that your solar panels need to be flexible, a rigid but foldable solar panel will often provide better performance and durability at a better price. Be sure to check out our article on foldable solar panels to learn more.
Types of flexible solar panels
There are two types of flexible solar panels that you’ll come across: thin film and crystalline silicon.
Thin-film solar panels
Thin-film is a type of solar cell where the photovoltaic material is essentially printed onto a surface. This is very different from the more common crystalline silicon solar cells that are used in most solar panels.
Flexibility is one of the main advantages of thin-film solar cells. Thin-film cells can be bent and even rolled. They can be placed on many different materials including glass, metal, and even fabrics. Because of this property, thin-film is sometimes used to make highly flexible, small solar panels for portable applications.
While thin-film solar has a lot of promise, crystalline silicon has a much larger global market, making it cheaper than thin-film. It also is less efficient than crystalline silicon, and many of the materials used, such as cadmium telluride or copper indium gallium selenide, are toxic.
Because of these disadvantages, thin-film isn’t very widely used. Still, this could change. For example, First Solar makes innovative thin-film based solar panels with high output. It’s also one of the larger US solar manufacturers.
Crystalline silicon solar panels
Most solar panels used today are made with silicon, which is the primary element in beach sand. The two types of solar cells on the market are polycrystalline and monocrystalline.
With both, the cells are made by cutting wafers of silicon out of a block. The cells are wired together to make a panel.
In a conventional panel, the individual wafers are thick and not flexible. But it turns out that if you cut the wafers thin enough, they become fairly flexible while retaining their photovoltaic properties.
The result is a solar cell that can bend at about a 30 degree angle. While this is less flexible than thin-film solar, it’s well suited for a lot of applications where you want the solar panel to conform to a curved surface, such as the roof of an RV.
Plus, these cells can be made of the same silicon as conventional panels, including high efficiency monocrystalline, gaining the benefit of economies of scale. For example, SunPower uses their Maxeon cells in both conventional rigid solar panels as well as their line of flexible panels.
Because of these advantages, all of the recommended panels in this article are crystalline silicon.
Disadvantages of flexible solar panels
Given the benefits, you might wonder why all solar panels aren’t made to be flexible. Well, there are some tradeoffs.
Because of the thinner silicon, flexible solar cells are less durable over the long run. Also, instead of being protected by a thick layer of glass and a rigid alumimum frame, they are attached to flexible sheets subjecting them to more stress over their lifetime. Eventually, wiring can fail or cells can crack.
Because of this, flexible solar panels have shorter warranties. For example, conventional SunPower solar panels with Maxeon cells come with a 25 year warranty on both materials and power production, but a SunPower flexible panel (also with Maxeon cells) has only a 2 year materials and 5 year power warranty.
If you need a portable solar panel but can sacrifice a little weight in exchange for better durability, consider a foldable solar panel instead.
Features to consider when shopping for flexible solar panels
Solar panel wattage
The advertised power output of a solar panel likely isn’t what you’ll see in the real world. The nameplate rating of a solar panel (in watts) is always the standard test conditions (STC) rating, which is a laboratory test standard under ideal conditions - but those ideal conditions are rarely encountered in the real world.
Instead, you want to look for a more realistic test rating, which include the CEC, PTC, or NOTC test standards. While these ratings are always provided with solar panels for residential or commercial use, lower cost flexible solar panels don’t always come with detailed specifications.
As a rule of thumb, you can estimate that your solar panel will produce about 75% of its STC rated power under ideal conditions: this means cool weather, bright sun, and an orientation perpendicular to the sun. The upshot is that if you buy a 100 watt flexible solar panel, expect it to produce about 75 watts at most. You might get lucky and see better performance, but 75% gives you a good margin for error.
If you need more power, you can always link multiple panels in series or parallel.
Nominal, operating, and open circuit voltage
Voltage can get a little confusing. When you shop for flexible solar panels, they’re usually intended for portable applications such as RVs and camping. This world is designed around 12 volt DC devices.
Because of that, these panels are typically advertised as either 12 volt or 18 volt panels. But that’s not the actual voltage that comes down the wire. Voltage will vary with the amount of sunlight, so you will typically see a few different things listed in the specifications:
- Nominal voltage refers to the intended application. This is usually the voltage you see advertised. In this category, most of the time the panel will be listed as 12v or 18v.
- Operating voltage is the maximum voltage the panel will output in bright sun. In this category, you’ll typically see a rating between 15-22v.
- Open circuit voltage is the maximum potential voltage of the solar cells in the panel. As a practical concern, this rating isn’t as useful to know as the others.
An important point is that if you want to charge a 12v battery, you need a panel with a higher voltage. This is why a panel advertised as 12v will typically have an operating voltage around 18v or so. It simply means that it has enough voltage to charge a 12v battery.
Keep in mind that when you wire multiple solar panels in series, the voltage is added together. For example, if you wire two panels with an operating voltage of 18v in series, their combined operating voltage will be 36v. This can be useful for raising the voltage if needed. (Wiring panels in parallel does not increase voltage.)
MC4 connectors and cables
With solar panels in this category (and larger) the MC4 connector is the standard for wiring cables.
The MC4 standard has a female and male connector and allows for a waterproof connection that clicks easily into place. The typical wire will be 10-gauge, giving you the ability to use quite long cable runs with less electrical resistance.
A solar panel will have a junction box with a pair of MC4 connectors, which is where the electrical connection is made.
You’ll need a cable to connect the panel to your battery or device. The cable may have MC4 connectors at both ends or a different type of connector at one end, such as a round DC plug, to allow you to connect to different devices. Check the package to see if it comes with a cable or if you’ll need to buy it separately.
A solar panel can have a rating for how much pressure it can withstand on the front and rear of the panel. This is often referred to as the snow load (front) and wind load (back).
Any solar panel approved for rooftop or utility use will have a rating of 5,400Pa/2,400Pa, but flexible panels don’t always have one. If your panel will be subject to some abuse from the elements, look for a panel with a strength rating.
When it comes to rain or salt spray (like you would encounter on a boat) the most vulnerable component is the junction box, which is why you should look for a waterproof rating. Check out this explanation to learn how to read the ratings. You will typically see ratings between IP65 and IP68, where a higher number is more waterproof.
ETFE is better than PET
Flexible solar panels are constructed by sandwiching the solar cells between layers of a polymer. Cheaper panels will use a polymer called polyethylene terephthalate, while better panels will use ETFE (ethylene tetrafluoroethylene). ETFE has slightly better light transmittance compared to PET, and is also more durable, which is an important consideration when your panel is exposed to the heat and rain on top of your RV’s roof.
5 recommended flexible solar panels
Best overall: Renogy Flexible Monocrystalline Solar Panel (50W, 100W, 160, 175W)
- Available in 50, 100, 160, and 170W sizes
- Operating voltage: 18.5V to 19.5V
- Long warranty (25 year power, 5 year product)
- High efficiency monocrystalline
- Reputable US-based company
The Renogy series of flexible monocrystalline solar panels is your best overall value if you’re needing a well-made flexible solar panel. Constructed with 21% efficient monocrystalline silion, this panel will produce a lot of power with a relatively small footprint.
The Renogy panel comes with an excellent 25 year power and 5 year product warranty, which is longer than warranties offer by other companies, including SunPower.
Renogy is a US-based company that makes a wide variety of solar products.
Amazon rating: 4.6 stars
Price: about $100 to $300
Rich Solar 100 Watt Flexible Monocrystalline Solar Panel
- Available in a 100W size
- Cheap price
- High efficiency SunPower cells
- Black panel
- Operating voltage: 18.6V
- IP67 waterproof junction box
- Warranty: 25 year power, 1 year product
- US-based company
Available in a 100 watt size.
Rich Solar is based in Montclair, CA and makes a variety of small solar panels and related gear. As another US-based company, this is a good choice if you want a better chance of getting customer service if needed.
This 100 watt panel uses very high efficiency SunPower cells. For comparison, it’s about 6 inches shorter than the Renogy 100 watt panel above but has the same power rating.
The cells for this panel are mounted on black ETFE plastic. You might choose this for aesthetic reasons, but the darker color will have a very small impact on energy production: solar panels don’t perform as well when hot. However, the impact probably will not be noticeable.
It’s about $40 cheaper than the Renogy panel, making it a good deal. However, you get only a 1 year product warranty, so it may not be as robust.
It has an Amazon rating of only 3.6 stars, but that’s based on just 8 ratings. (The Renogy panel above has 733 ratings.)
Amazon rating: 3.6 stars
Price: about $140
SunPower Flexible Monocrystalline High Efficiency Solar Panel
- Available in 50, 100, 110, and 170 watt sizes
- High efficiency SunPower cells
- Operating voltage: 17.6-29.4V
- IP67 waterproof junction box
- Warranty: 5 year power, 2 year product
- US-based company
These panels are made with SunPower’s line of Maxeon cells, the same silicon used in their conventional solar panels but manufactured thinner to make them flexible. These cells aren’t exclusive to SunPower: they’re used in the Rich Solar panels above and several others that you can find on Amazon.
Compared to the Rich Solar panel above, these SunPower panels are available in a wide variety of sizes, giving you options if you need different dimensions for your project.
The SunPower panel comes with a 5 power and 2 year materials warranty. This isn’t nearly as good as Renogy’s, but better than other competitors. If you want a flexible panel with SunPower cells, this product is probably better constructed than the many no-name brand manufacturers that also use SunPower cells.
Finally, these SunPower panels is the only one I could find with a full datasheet that includes all the technical specifications of the panels. Overseas manufacturers are particularly neglient when it comes to providing documentation, which makes SunPower a good choice if the technical specs are critical information for you.
Amazon rating: 4.8 stars
Price: about $75 to $375
Winnewsun Bifacial 100 Watt Flexible Solar Panel
- Available in a 100W size
- Operating voltage: 20V
- Unique bifacial design harvests sunlight from front and back of panel
- Smaller footprint than other flexible 100 Watt panels
- 5 year product warranty
- Taking full advantage of the bifacial cells requires special mounting
This flexible solar panel by Winnewsun is unique among all the panels listed on this page because it is a bifacial panel.
A bifacial solar panel is constructed to be transparent in the rear, allowing the solar cells to capture sunlight from both the front and back of the panel. This makes the panel more efficient in terms of electricity generated per square inch because it can capture sunlight reflected from the ground, or whatever surface is behind the panel.
Don’t expect a doubling of efficiency: depending on how reflective the surface behind the panel is, you can expect an average power increase of 6-9%, although if you correctly install this above the bright white roof of an RV, you can probably expect to exceed a 9% gain.
If correctly installed to maximize front and rear sunlight capture, the result is the same energy generation as a monofacial panel in a smaller footprint. This panel is 908 square inches in area, compared to 1,005 square inches for the Renogy panel.
Keep in mind that it doesn’t make sense it buy this panel if you intend to velcro or glue the panel to the roof of your RV. Instead, you want to use this panel with some type of tilted frame so that it can benefit from reflected sunlight that hits the back of the panel. One option could be to mount the panel to a sheet of plexiglas.
This product comes with a five year warranty, which is better than many other flexible solar panels.
One cautionary note: I couldn’t find any information the manufacturer, except for what is listed on their Amazon page. That said, the product manages a respectible 4.2 stars on Amazon.
Amazon rating: 4.2 stars
ECO-WORTHY Shingled 100 Watt Flexible Solar Panel
- Available in a 100W size
- Operating voltage: 19.2V
- Shingled design eliminates spacing between cells
- Includes 2.9" cable
- IP68 waterproof junction box
- 1 year product warranty
Most solar panels use individual solar cells that are mounted as a spaced grid. This ECO-WORTHY panel uses a different approach with solar cells that are layered together like roofing shingles. This method eliminates the gap between the cells, and increases the efficiency of the panel.
This gives a nice aesthetic appearance to the panel, which might matter to you. It also comes with cables that are nearly 3 feet long, which is more convenient than the very short cables some other manufacturers provide.
Overall, this panel gives you high efficiency at a good price.
Amazon rating: 4.4 stars
Price: about $136
Maintenance tips for flexible solar panels
Flexible solar panels are a great product for certain applications, but the tradeoff is lower durability and a generally shorter lifespan. To maximize the life of your product, follow these tips:
- Never step on them. If you’re working to mount these panels on the roof of a vehicle or structure, be careful to not step on them. While it might seem like they’re durable enough, stepping on silicon solar cells can cause invisible microcracks that compromise the energy production and longevity of the product.
- Store them when not in use because UV light and exposure to the elements will degrade your panels over time. If you’re mounting these on a vehicle, consider using velcro to secure them to the roof so that you can easily remove and store them when not needed.
- Even though they’re bendable, avoid bending them as much as possible. These solar panels are flexible within limits, but they will eventually crack if stressed too far. To minimize the risk of damage, handle them carefully and flex them only as much as needed to fit the surface that you’re installing them onto.
- Store them gently. For similar reasons, you want to store these panels gently. Keep them flat and don’t stack anything on top of them.
- Clean them periodically. The maximize power performance, keep these panels clean. Be sure to remove any bird droppings that land on them, which can have a corrosive effect on the plastic. Clean them gently with plain water to avoid scratching the surface.
Related equipment to consider
If you’re using these panels to charge a battery, you’ll need a charge controller.
For mounting on a vehicle such as an RV or boat, mounting brackets, wiring and MC4 connectors, and proper adhesives are the equipment you’ll need. Read our guide on RV solar panels to learn more.
Foldable solar panels are a more durable but heavier alternative to flexible panels.
Choosing a solar panel kit is often a cost-effective alternative to buying items like cables and charge controllers separately.
If you only need to charge a small device, consider these portable solar panels with USB ports.
For keeping your phone, table, or small laptop charged, solar phone chargers and rechargable batteries are a good choice.