Beginner’s guide: How to power an RV or boat with solar panels
Got a camper that you want to power with solar panels? If you spend time away from hookups, it can be a great way to get clean, quiet power. Here's a guide on how it works.
Wouldn’t it be cool if you could power your recreational vehicle entirely with solar power?
Turns out you can! A group in the Netherlands have built exactly that: the Stella Vita is a fully electric camper vehicle with slide-out solar panels. It has a 60 kWh lithium-ion battery and a body constructed of aluminum and fiberglass. With good sun, it can fully recharge itself within 2 or 3 days. It seats two and weighs only 3,700 lbs.
But that’s not what most Americans have in mind when it comes to recreational vehicles. Many motorhomes are behemoths and can weigh as much as 25 tons. Sticking a few solar panels on the roof isn’t going to meet the energy requirements of a vehicle like that.
However, that doesn’t mean your camping can’t benefit from having a few solar panels available. Installing solar on your RV can be a DIY project, and this article will try to help you decide if it’s a project worth undertaking.
Note: while this article is aimed at motorhomes and camper vans, the basic advice is useful for boats as well.
Should you install solar panels on your RV?
If you only ever go to RV campsites with electrical hookups, it’s probably not worth it to worry about solar. Electrical hookups at campsites are typically 30 amp @ 120v or 50 amps at 240v, which are far more than what you’ll get from a few solar panels that you carry around.
It’s not really worth it from an environmental point of view either. Rooftop solar panels pay back the energy used in their own manufacturing within a couple years. RV solar panels, on the other hand, are used intermittently. They don’t have the opportunity to generate much electricity in their lifetime.
However, if you sometimes camp at sites without electricity - also known as boondocking - solar panels can be a great tool. While you could use a generator, you don’t necessarily want the noise and smell of a generator while you’re trying to enjoy the great outdoors.
Similarly, if you’re a boater, solar panels can keep your beer cold and the stereo blasting without you having to interrupt the party by firing up your engine to charge the battery.
If it sounds like solar would be helpful to you, then this guide will introduce the basics of everything you need to get started.
Types of RV solar panels
You can either install solar panels on the roof of your RV or carry them around in storage and pull them out as needed. Depending on what’s better for you, there are rigid, foldable, and even flexible solar panels.
Conventional silicon solar panels
Solar panels intended for the home are quite large, usually about 60 inches by 40 inches in size, and produce anywhere from about 260 watts to more than 400 watts, depending on efficiency. This is too large to either mount on the roof of RVs or keep in the storage bay, which is why RVers usually go with smaller panels in the 100 watt to 150 watt range.
These panels are less than half the size of a residential panel, making it easier to fit these panels around the various vents on your RV roof.
One option with these panels is to store them out of the way while you’re driving, and then pull them out and place them on the ground once you’ve set up at your campsite. Some panels have frames with built-in kickstands designed for this purpose, or are designed to fold up neatly for storage. There’s some options listed at the bottom of this article.
Bendable crystalline solar panels
Flexible solar panels are a cool choice if you want to attach the panels to the roof of your vehicle or want an extra lightweight option.
These panels are made of silicon solar cells, just like those used in conventional solar panels, but the cells are manufactured much thinner. This allows them to bend without breaking - usually up to about 30° of bending. This type of solar module isn’t as completely flexible as thin-film panels (which are based on a different chemistry). You can’t roll them up into a tube like you can with thin-film, but they are flexible enough to conform to the curve of your roof.
These panels don’t use glass and an aluminium frame, but are instead laminated between polymer sheets. Flexible solar panels may weigh only 20% as much per watt of power as a conventional panel. The tradeoff? They’re less durable than a normal panel.
Check out our article on flexible solar panels to learn more and see some product options.
How solar charge controllers work
You aren’t going to directly use the electricity your solar panels generates. Instead, you’re going to use that electricity to charge the house battery in your vehicle.
Safely charging a lead-acid battery involves carefully monitoring the input voltage to ensure that it stays within the correct range. That’s the job of the charge controller in your photovoltaic system.
The charge controller takes the electricity from your solar panels and sends out electrical current with the correct voltage to your battery. It will automatically monitor the voltage of the battery as it’s charging, adjust the output as the battery “fills up”, and switch to float (trickle) charging to keep the battery safely topped up without overcharging.
As an additional safety mechanism, some charge controllers include a temperature sensor to ensure that the battery isn’t dangerously overheating while it’s being charged.
You can choose between a less expensive pulse width modulated (PWM) charge controller and more sophisticated (and expensive) maximum power point tracking (MPPT) controllers.
As you might have guessed by now, I also have an article about charge controllers.
How many solar panels do I need to power my RV?
If you want to fully power your RV with solar, you’ll need to take an inventory of how much power your appliances use. You’ll also need to know the capacity of your battery.
Power usage, as far as your battery is concerned, is measured in amp-hours (Ah). Check the label of your battery: it’ll tell you the capacity in amp-hours. One amp-hour of capacity means that the battery will support one amp of current for one hour.
For example, let’s say that you use 200 amp-hours in a day. Multiply that by 12 volts to convert your amp-hours to watt-hours. That means 2,400 watt-hours a day.
Now, divide that by how many hours of full sunshine you get to find out how many solar panels that is. Let’s say we get the equivalent of 8 hours of full sunshine a day.
2,400 watt-hours divided by 8 hours is 300 watts.
That conveniently happens to be three 100 watt solar panels, which would work out nicely.
However, you should understand that the label efficiency of solar panels is rarely achieved in the real world. Shading, soiling, and high temperatures make your solar panels less efficient. Read our guide to solar panel specifications for an indepth understanding of this topic, but as a general rule of thumb you should expect your solar panels to achieve, at best, only 75% of their nameplate rating.
That means our 100 watt solar panel will probably only generate 75 watts of power in real conditions. For our example of using 2,400 watt-hours a day, this means adding one more 100 watt solar panel to our array.
Options for mounting solar panels on your RV
You can do a semi-permanent installation of solar panels on your RV. Common choices are to place them on the roof and to mount them as movable awnings to shade your windows.
Placing solar panels on the ground is also a perfectly good choice - sometimes better, because you can move your panels around to find the best sunlight and while still having the option of parking in the shade. If you’re going that route, you’ll want conventional solar panels and a tiltable bracket.
Drill-free mounting solar panel brackets for roof mounting
If you’re using conventional solar panels and you want to attach them to your vehicle, there are a couple options available. A common way is to use aluminum z-brackets, but these require you to penetrate the roof of your vehicle with screws. One good alternative is to use drill-free corner brackets. Instead of screws, these are attached to your vehicle using very strong adhesives.
This one is made by Renogy. It’s preferable because it has six attachment points rather than the four offered by other manufacturers.
It’s currently selling for $27. (Get current pricing on Amazon)
The panels themselves are screwed into the brackets, but adhesive is used to fix them to your roof. You might wonder if glue is strong enough to keep the panels from flying off when you’re driving down the highway. There are two extremely strong glues that we can recommended: a polyurethane adhesive made by Sikaflex, and VHB (very high bond) double-sided tape made by 3m. This tape has a tensile strength of 90 pounds per square inch, so it’s not like the duct tape you have in your drawer.
Use the links below for pricing.
Tiltable solar panel mounting brackets
Tiltable aluminum mounting brackets let you angle your panels to maximize the electricity you harvest. These are used with conventional solar panels and can be installed on the roof of your vehicle with screws and sealant.
If you don’t want to drill holes into your roof, these brackets also work perfectly well as solar panel stands that you can simply place on the ground.
This model from Link Solar comes in a range of sizes, including lengths that fit 100 watt panels, which are commonly used for RVs. The black knobs make angle adjustments easy, and the whole bracket will fold flat for driving or storage.
The bracket comes in 22-inch, 28-inch, and 41-inch lengths to fit a variety of solar panel sizes. It starts at $46. (Get current pricing on Amazon)
If you roof mount them, they need to be screwed in, and then you seal the hole with an appropriate sealant. A good choice is Dicor’s Lap Sealant, which will adhere to both TPO and EPDM roofs. It also sticks to aluminum, mortar, wood, vinyl, galvanized metal, fiberglass and concrete, so it’s pretty much an all-purpose product. One tube costs $10. (Get current pricing on Amazon)
The standard connector for solar panel wiring is the MC4 connector. They come in male-female pairs that simply plug together.
If you have multiple solar panels in your system, you’ll need MC4 branch connectors to join the individual panels into a common wire that feeds your charge controller. (Search MC4 branch connectors on Amazon)
What type of wiring do I need?
When dealing with DC power, you want to use a fat cable to minimize power loss due to electrical resistance. 10 gauge (10AWG) is a good choice. Look for 10AWG cables designed for solar, because they come with MC4 connectors built in.
Bottom line: solar panels aren’t for every camper, but handy if you need them
Solar panels aren’t really helpful if you mainly stick to campsites with hookups, but you’re the type who likes to spend a week boondocking, solar panels can help keep the battery in your camper charged without having to resort to a noisy generator.
Fortunately, there are plenty of product options and even complete solar panel kits that including charge controllers and wiring so you don’t have to figure out all of the components you need.
One last option worth mentioning is solar generators, which really are just big portable lithium batteries with charge controller built in. They’re a nice option if you’ve got devices that could benefit from a portable battery, or if you want a battery with more advanced chemistry than the typical lead-acid house battery that RVs use.