RV Solar Panels: What You Need To Know
(Camp Addict does NOT accept payment from any company to review or endorse their products.)
It's pretty clear... one of the most popular (and misunderstood) topics talked about amongst RVers is solar power.
Mostly, those who have been doing it a while talk about their battery bank or adding some new panels.
However, beginners have all sorts of questions.
- Do you need RV solar panels?
- If so, portable or rooftop RV solar setup?
- How much solar power do you need?
- What charge controller is the best?
- Monocrystalline or Polycrystalline solar panels? -on and on, you get the idea.
These are great questions and the answers aren't so simple. That's because there is a LOT to know.
As full-time RVers and full-time boondockers, Camp Addict Kelly and Marshall have been learning about and using rooftop and portable solar panel setups for a combined total of 13 years.
In December 2018, we installed a 600-watt rooftop solar system on Kelly's rig, complete with a solar controller and battery monitor. (No inverter was needed.)
Marshall installed a similar system on his RV in June of 2020.
So, we know a thing or two, enough to produce for you this information. We hope it is as easy to understand as possible.
Read on for our very in-depth RV solar panel educational guide.
Ready to go off-grid and get started with RV solar panels? Click the button below to read our portable solar panel reviews.
Your Guide To Everything About RV Solar Panels
There's sooooo much to know when it comes to solar panel use, right? Amps, watts, volts, battery controllers.
It's electricity, which is complicated and tricky. It can make you want to pull your hair out!
If you are anything like Camp Addict Marshall, you don't have extra hair to spare. (heh)
So let's teach you what you need to know about solar panels for RV use. Then you'll know what to get and how to use it.
Do You Need An RV Solar Power System?
Not everyone benefits from an RV solar system. There are a great number of campers that don't need any kind of solar set.
Solar power serves a single purpose - to charge your RV batteries.
In other words, it charges when you are off the electrical grid (off-grid).
That's it. Simple, right? Well, yes and no.
Are You Ever Off-Grid?
Technically every RV is "off-grid" a lot of the time. For example, when driving down the road to your next destination, you're off-grid.
You aren't trailing an extension cord that is 200 miles long, are you? Nope, you sure aren't.
So, you are technically off-the-grid during those times. However, that doesn't automatically make you a candidate for solar power.
If your rig has an engine, it has one or more alternators providing power to the house batteries (the batteries that power all the 12-volt systems in your rig).
Trailers usually have an 'umbilical cord' that charges the tow vehicle batteries while driving down the road.
Reasons You Don't Need Solar
If you only move from campground to campground where you are plugged in, then you likely don't need an RV solar setup.
Likewise, if you only occasionally camp 'off-grid' (dry camping) you also may not need a solar power system for RV use
Instead, you might have enough house battery capacity to make it through a couple of days of use. (Without discharging your lead-acid batteries below 50%.)
Once you are done camping for a few days, you can head home, plug in, and top off your batteries.
Reasons You Do Need Solar
The type of camper that benefits the most from RV solar systems is one that boondocks extensively, or boondocks with very little battery capacity.
Take for example Camp Addict Co-Founders Kelly and Marshall. They both boondock exclusively and are ALWAYS unplugged.
While this may change in the future, they still foresee themselves as boondocking 99% of the time. So, they need RV solar panels to keep their batteries charged.
Otherwise, they would have to run RV generators all the time. Who wants to listen to generator noise while camping in serenity?
Here's a hint: NOBODY.
So, if you are in campgrounds full-time, you can probably live without solar power for RV use, especially if you have a generator.
If you boondock all the time, an RV solar setup is nice instead of using generators all the time.
Portable Solar Panels Versus Roof-Mounted Solar Panels
Once you've decided you are a candidate for an RV solar system to charge your batteries, the next question is what type? Rooftop or portable solar?
There are pros and cons to both approaches.
Keep in mind that a portable solar system maxes out at about 200 watts.
Sure, you can buy multiple portable systems and connect them to a single solar controller. But there comes a point when it becomes a true pain in the behind having a bunch of portable panels strewn about.
Still, it's possible!
If you need a lot of RV solar capacity, you may want to consider having a combination of permanently mounted rooftop panels as well as a portable panel.
Roof-Mounted RV Solar
Solar panels for RV roof use are the easiest to deal with. They are permanently mounted up on your roof.
You don't have to 'deploy' them at every new campsite. (Also, you can't run them over. LOL!) They are always just there. But they may be overkill for your situation.
However, if you like to tuck in amongst the trees for shade, a roof-mounted RV solar system obviously isn't going to produce much solar energy.
Roof-Mounted Solar Panels Pros and Cons:
Portable RV Solar
A portable solar system has its place in the RV world. No question about it!
It's true that a portable setup is a great way to dip your toes into the world of RV solar power.
It's pretty much the perfect solution for someone who likes to dry camp but doesn't need a full-blown roof-mounted RV solar setup.
Portable RV Solar Pros and Cons:
You Can Always Start With Portable
If you don't think you are going to need much solar power, or you cannot justify installing roof-mounted solar panels, a portable system is a great option.
They also are a great way to add to your existing roof-mounted RV solar panel system (and give you a bit more flexibility as far as where you can park).
Marshall's Portable Panel Story
Camp Addict Co-Founder Marshall purchased his Lance travel trailer with a factory-installed 160-watt roof-mounted RV solar panel system.
Once he started boondocking, it became clear that a larger solar energy source was necessary.
Rather than install another roof-mounted solar panel, he opted to go with a portable 100-watt solar panel system that is 'ground deployed'.
Why did he choose portable instead of roof-mounted?
A couple of reasons:
- Winter sun is a low sun. Therefore, flat roof-mounted RV solar panels don't provide as much solar energy production in the winter as they do during the summer. Having a ground deployed panel that is tilt-able and can be pointed directly at the sun at the optimal angle is much more beneficial (unless you've got a bunch of space and disposable money to put a lot of RV solar panels on your roof).
- He wanted the ability to park his travel trailer where he wanted without worrying too much about shading the roof panel. There are times when the perfect shade tree appears. It will provide relief from the harsh afternoon sun but also shades the rooftop solar panel. Having a ground deployed portable solar panel means the trailer can be shaded in the afternoon, yet the house batteries are still getting charged. Win-win!
Kelly's Portable Panel Story
Camp Addict Co-Founder Kelly used portable panels for a few years without having a roof-mounted RV solar system.
This solar setup served her well for a few years, even though it was a huge pain in her butt to deal with two sets of ground deploy solar panels. And Kelly, being hard on her gear, kept breaking panels.
Anyway, the two panels usually were barely enough to keep her batteries topped off. Unless it was cloudy.
In December 2018, Kelly and Marshall installed 600-watts of solar on her roof. Soon after that came a couple of lithium batteries.
Consequently, gone are her days of dealing with RV solar panels on the ground or worrying about if her power supply would last if it got cloudy.
How Much Solar Power Do You Need?
The 10 million dollar question is 'how much solar power do I need for my RV'?
Q: How many watts of solar power do you need in order to have enough solar energy coming in to both charge the batteries and be a power source for energy used during the day?
A: It depends. (Sorry!!!!)
(So freaking annoying, right???)
Ask 100 people online much large of an RV solar system you should get and then sit back, grab some popcorn, and enjoy the show.
This is an area where many people are incredibly
How large should a solar system for RV use be? There is no easy/stock answer.
Factors That Affect Battery Performance
There are SO MANY factors that come into play when it comes to how much solar energy capacity you need.
For example, temperature is a HUGE factor in how much usable capacity you will get from your house battery bank. Let us explain.
Lead-acid batteries (most commonly used) are rated to have a certain amp-hour capacity. This is pretty common knowledge.
What ISN'T common knowledge is this: batteries are rated at X amp-hour capacity at a certain temperature - normally about 77ºF (25ºC).
Any deviation from that temperature, and you have a battery with a shorter life span (if too hot), or colder than optimal, you will have a lower usable amp-hour capacity (but battery life will increase).
Now you see why we love chasing the perfect 74º temperature, haha.
Battery capacity has a fairly linear relationship to the outside air temperature (and therefore, battery temperature):
- Batteries do not like heat. As it turns out, each 15ºF rise in temperate above the optimal 77ºF temperature will result in a halving of the batteries' life, though capacity will increase by 10%.
- On the flip side, batteries love cold as far as their lifespan is considered, but not so much when it comes to usable amp-hour capacity. Every 15ºF decrease in temp below the optimal 77ºF results in a 10% decrease in capacity (but battery life increases).
So when you need battery capacity the most, i.e. when it's freezing outside and you run the power-hungry furnace a lot, your battery capacity will be significantly reduced.
You won't get as much time between charges.
Test At Different Temperatures
Why does all this temperature talk matter?
Because the easiest way to figure out how much solar energy production capacity you might need is to go out and camp off-grid.
In other words, use your 12-volt electrical system just as you normally would without plugging into shore power, a generator, or an RV solar system.
Depending on what time of the year you do this test, and the outside temperature, you will get different results.
So, this is only a rough estimate at best.
Amp-Hour Consumption Basics
The first thing you need to know is the amp-hour rating of your batteries. How do you find it?
Well, you would hope it would be listed on the battery, but this is often not the case.
Here's how to find out the amp-hours:
First, You Need To Know 2 Things:
- If your battery bank consists of 12-volt or 6-volt battery(ies).
- What the amp-hour rating of each battery is.
Find Your Battery Maker and Part Number
Start by looking at your battery label. It might be located on the top, OR the side of your battery(ies).
There, it will list who made it and the battery part number.
Most likely the label will not have any information about the voltage of the battery or the amp-hour rating. (Ridiculous, right?) Therefore, you have to search for it on the internet.
Enter the manufacturer and part number into Google. This should take you to some sort of battery specification page.
It will tell you the voltage and the amp-hour rating.
Look for the amp-hour rating at 20 hours of use (abbreviated as 'Ah @ 20hr' or '20HR rating' or something similar).
This is the industry standard number that people are referring to when they are talking about the amp-hour rating of a battery’s capacity.
Example: Using the Centennial Battery label above as an example, we enter 'centennial battery dc24mf' into Google and find this battery information page with the information we are looking for (look through the information to find what you are looking for): 12-volt and 75 amp-hours!
Finding Total Amp-Hours For Your Battery Bank
One battery: Easy. If you only have one, your amp-hour rating is the Ah @ 20hr rating stated on the battery spec page.
Multiple Batteries: If you have multiple batteries (we will use two batteries for our explanation purpose), then you have some figuring out to do.
First, you need to know if your batteries are connected in series or parallel. This step is pretty easy once you know if you have 12-volt or 6-volt batteries.
In brief, a battery bank consisting of two 12-volt batteries will be wired in parallel. Accordingly, two 6-volt batteries will be wired in series.
This is always the case when you have two batteries.
Now to calculate the battery bank’s amp-hour rating.
Continuing to use our example of the Centennial Battery, we found out that the part number DC24MF is a 12-volt battery with a rating of 75 amp-hours (Ah @ 20hr).
With a 2 battery system wired in parallel, we can calculate that the overall system voltage remains at 12-volts, but the amp-hour rating is doubled to 150 amp-hours (75 amp-hours x 2).
How To Figure Your Amp-Hour Consumption
Here's what you need to do to get a rough estimate as to your daily amp-hour power consumption:
How To Check Your Battery Voltage With A Multimeter
Testing Temperature Matters!
Battery testing is where outside temperature comes into play.
Ideally, you should do this test when the outside temperature is 77ºF, but good luck with that. Days will be hotter than nights.
You may do this test in the dead of winter in some cold location and never see anywhere close to 77ºF, even during the day.
So, yeah, this test has some flaws, but without springing for a fancy battery monitor, this is as good as we get if you want an easy way to guesstimate how much power you use.
How Many Watts Of Solar?
Now that you have a (very) rough idea of how many amp-hours of electricity you use per day, it's time to figure out how much solar you need.
Here we go with another 'rule of thumb'. A 100-watt solar panel will generate approximately 30 amp-hours per day.
Using our fake test data from above (33 amp-hours consumed on average per day), we can get an idea of a good starting point for pondering how much solar energy capacity you need.
The Important 50% Rule
With lead-acid batteries (the most common type used), NEVER go below 50% charge.
While the above chart indicates that 40% charge is still 'in the green', try not to go below 50% state of charge.
Your batteries will love you for this and will reward you by having a long, healthy life. Going below 50% more than once will greatly shorten its life.
Since a 100-watt solar panel will produce somewhere in the neighborhood of 30 amp-hours per day, it won't be enough capacity for our sample RVer.
So, that means you are looking at at least a 120-watt RV solar panel kit, but in this scenario, you'd be smarter to purchase a 160-watt or even a 200-watt solar panel system.
Why would you want to buy more solar than you calculated you need? If you have cloud coverage, your solar isn't going to produce anywhere near its rated output.
Therefore, having an excess of solar energy producing capacity on cloudy days is a good thing.
Though, you probably will not have enough solar panels to make up for truly bad weather.
Marshall does not have this kind of excess solar energy production capability. As a consequence, after a string of crappy solar days, he pulls out the generator.
Kelly is able to get by when faced with a couple of crappy solar production days with her 600-watts of solar panels on her roof, as well as her lithium batteries. Understandably, it helps she doesn't use a lot of power daily.
If you only camp where it's beautiful weather all the time (please excuse us as we laugh uncontrollably at the idea of the perfect camping weather all the time), then clouds aren't an issue.
If you are like the rest of us and live on planet Earth, you need to consider having excess solar energy capability.
This most likely means you need a decent number of solar panels on the roof. Similarly, you might benefit from supplementing it with a ground solar panel.
You can start out with a portable solar system and see how well it fits into your style of camping and power usage.
Should you find that your initial ground deploy solar panel purchase isn't enough, simply add more solar later.
Polycrystalline or Monocrystalline Solar Panels?
RV solar panels are made with one of two types of solar cells:
The difference between polycrystalline (poly) and monocrystalline (mono) solar panel cells is in the manufacturing.
Monocrystalline: More expensive but more efficient.
Polycrystalline: The cheaper of the two, slightly less efficient than mono cells, and are made by many silicone crystals/fragments.
Mono solar cells are cut from a single silicone ingot and are smaller sized than poly when you are comparing same solar energy production capability (watts).
Individual monocrystalline cells have a distinctive square with cut-off corners appearance.
A poly solar cell system is somewhere in the neighborhood of 13-16% efficient while a mono solar cell system is about 15-20% efficient.
Most quality RV solar panels are made from monocrystalline (mono) solar cells because of the greater efficiency of a mono cell system.
This results in a smaller overall size for a given wattage, therefore taking up less roof space, or storage space (in the case of ground deploy solar panels).
Plus, they are lighter (again, for a given wattage of solar energy production).
Poly Solar Cell Pros And Cons:
Mono Solar Cell Pros And Cons:
So, what type of solar power system for RV use do you purchase?
Monocrystalline or polycrystalline? The best solar panels come with mono cells.
The cheap RV solar systems most likely come with poly cells, though as far as rooftop setups, these are becoming increasingly uncommon.
With portable setups the poly solar panel systems also come with crappy solar controllers, undersized wiring, and a cheaply made frame and leg setup.
When it comes to lightweight options and roof space, we recommend monocrystalline RV solar panels.
Solar Charge Controllers Explained
What does a solar charge controller do?
It regulates the amount of voltage that gets transferred from the solar panels to the house batteries. The charge controller will 'read' the battery voltage.
Then, they will change the voltage going into the batteries from the solar panels depending on the current state of charge.
Types Of Solar Charge Controllers
Charge controllers come in two 'flavors':
- PWM (pulse width modulation)
- MPPT (maximum power point tracking).
PWM controllers are less efficient, but are also cheaper than MPPT controllers.
These controllers are what come with portable panels, as well as most factory RV solar panel installations, so they are our focus here.
PWM Charge Controllers
A PWM charge controller isn't very efficient in converting the incoming solar energy (sunlight) from the solar panels to be used as available power to the batteries.
Because they are in the range of 75-80% efficient, whereas an MPPT controller is 94-98% efficient.
This is because a PWM solar controller is basically just taking the incoming voltage from the solar panels and reducing it to the level that the batteries will accept (without overcharging them).
This causes a reduction in available power from the solar panels.
(There is a 'fancy' formula for this calculation, but unless you are a total geek, it'll most likely cause your eyes to glaze over.)
When you are dealing with lower wattage systems, living with this inefficiency is a tradeoff. It keeps the overall price lower by not going with a considerably more expensive MPPT solar controller.
As RV solar power system sizes (overall wattage) grow, then the inefficiencies of a PWM controller become much more noticeable.Therefore, MPPT controllers are generally used.
For this type of situation, the controller is still more expensive but it will be a much smaller percentage of the total system cost.
Solar Controller Charge Stages
A solar controller will have a certain number of charge stages. A stage is the actual voltage that is being used to charge the batteries.
There are three basic stages (A 3-stage charger uses all three):
- Bulk charge - 100% of available power from the solar panels is used to charge the batteries until the absorption voltage is reached (generally 14.4 to 14.6 volts).
- Absorption charge - Once a set voltage is reached (normally in the 14.4 to 14.6-volt range), the charge controller will switch to the absorption stage. At this point, the battery is charged to somewhere in the neighborhood of 85% of full charge. The solar charge controller will then maintain the absorption voltage (again, typically 14.4 to 14.6 volts) for a set time (1 to 2 hours). Both voltage and time period varies depending on the solar controller manufacturer.
- Float charge - After the absorption charge 'session' is complete, your batteries are pretty close to fully charged. The solar controller will bump down the battery charge voltage to a range of 13.2 to 13.7 volts and hold this for the duration of the time sunlight is hitting the solar panels. This lower charge voltage ensures that the batteries aren't overcharged and that the battery acid isn't boiled off. If there is an excessive load on the batteries and the controller is no longer able to maintain the battery charge level at the float charge point, it may 'kick' back into bulk charge mode, increasing the voltage to the batteries. Also, it brings the batteries back up to fully charged, assuming there is enough solar energy output to do this.
While the above charge modes are what every PWM solar charge controller has in order to effectively charge batteries, there is another mode. It's called equalization.
This used to just be called 'equalizing the batteries' but someone who has a fancy marketing degree decided to call this a fourth charging mode.
Equalizing mode charges the batteries somewhere in the range of 14.8 to 15.5 volts (manufacturer dependent), which essentially overcharges the batteries causing gassing of the battery cells.
This makes sure that all cells of a battery bank have the same charge.
Generally, equalization is set to run every 4 weeks, though some controllers will automatically kick into equalization mode if the battery bank voltage drops below a certain level. This level is typically 10 - 12.1 volts.
That's a wide range, but again, different manufacturers have different ideas. They probably all think they are right.
Only flooded wet cell lead-acid batteries should be equalized (unless your AGM or gel lead-acid battery manufacturer says go for it).
Solar Charge Controller Displays
Decent RV solar charge controllers will have an LCD/digital display that shows you what is happening with the controller and batteries.
It tells you voltages, amperage, power usage, and probably more information than you care about.
They will also have LEDs that indicate charge modes, faults, or other gee-whiz details.
Solar controllers that come with inexpensive portable solar kits will only have LEDs, so they aren't of much use. But at least they will charge your batteries (in theory), right?
Able To Monitor Your RV Battery?
Another consideration of the solar charge controller is whether or not it has the ability to directly monitor the battery bank voltage and/or temperature.
This is important because monitoring the battery 'vitals' helps prevent damage from overheating and overcharging.
The ability to remotely monitor the batteries is nice to have.
However, plenty of people have lived without this ability for many years and probably will tell you their batteries did just fine.
Solar Charge Controller Battery Type Compatibility
Portable solar panel kits that have solar charge controllers included are all compatible with flooded, gel, and AGM style lead-acid batteries.
If you have lithium batteries, then you need to use a different type of solar controller - one that is compatible with lithium batteries.
Of course, you most likely will have a pretty massive solar array that has an awesome MPPT solar controller if you've gone the lithium route.
The Benefits Of Battery Monitors
Figuring out how much power you use, and therefore how much solar capacity you need, can be a bit of a black art.
There are so many variables - day to day variance of electrical use, cloud cover that reduces solar energy input, the outside temperature, etc, etc, etc.
One way to see exactly how much power is going into, and out of, your battery bank is to use a battery monitor.
This precisely measures the amount of electrical current flow in and out of your batteries.
If you want to get a truly accurate picture of how much solar energy production capacity you need to keep up with your power usage, then a battery monitor should be one of your RV camper must-haves.
The Victron BMV-712 is a popular choice because it is relatively inexpensive.
It comes with Bluetooth capability that lets the monitor communicate with a smartphone app (both iOS and Android).
Therefore, you can easily see what your batteries are doing.
(You can view information directly from the monitor, but the app makes it much easier.)
Victron BMV-712 Battery Monitor
Why not use a cheap plug-in battery monitor like the one below?
Because it doesn't keep track of the amperage used.
It only measures system voltage at the 12-volt outlet it's plugged into. Alternately, measuring directly at the battery is far more accurate as there is no voltage drop due to the RV wiring.
You need to use a TRUE battery monitor like the BMV-712 above to accurately track how many amp-hours you use, and therefore know how much solar capacity to purchase.
Solar panels are a fantastic way to keep your RV powered and your batteries charged. What you get depends on your particular power usage and needs.
You should have a pretty good understanding now of the basic concepts of solar and the pros and cons of a portable setup VS roof top solar panels.
Solar can be a game changer for many RVers. This is especially true for boondockers or people wanting to break their dependance of campgrounds.
Whether or not you think solar power is right for your style of camping, at least now you have a general idea of what is involved in harnessing this abundant power source from the sun.
He-llllo. I'm the co-founder of Camp Addict, which my biz partner and I launched in 2017. I frigging love the RVing lifestyle but in December of 2020, I converted to part-time RV life. Heck, I lived in my travel trailer for over 5.5 years, STRICTLY boondocking for pretty much all of it. Boondocking is a GREAT way to live, but it's not easy. Anyway, I'm passionate about animals, can't stand campgrounds, I hardly ever cook, and I love a good dance party. Currently, I can be found plotting and scheming whether or not to start collecting farm animals (or plotting my next RV trip!) at my beautiful new 'ranch' named 'Hotel Kellyfornia', in Southern Arizona.
Camp Addict co-founder Marshall Wendler brings his technical expertise to help explain RV products in an easy to understand fashion. Full-time RVing from April 2014 - December 2020 (now RVing about 50% of the time), Marshall loves sharing his knowledge of the RV lifestyle. Marshall spends the majority of his RVing life boondocking. He is the part of Camp Addict that knows 'all the things'. He's good at sharing his technical knowledge so you can benefit.