RV Solar Panels: What You Need To Know
(Camp Addict does NOT accept payment from any company to review or endorse their products.)
One of the most popular (and misunderstood) topics talked about amongst RVers is solar power.
Do you need RV solar panels?
If so, portable or rooftop RV solar setup?
How much solar power do you need for your RV?
What charge controller is the best?
Monocrystalline or Polycrystalline solar panels, on and on, you get the idea.
RV solar panel use is almost an inevitable topic of discussion among us.
There is a LOT to know.
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.)
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 RV 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.
So let's teach you what you need to know about solar panels for RV use so that you know what to get and how to use it.
Do You Need An RV Solar Power System?
Not everyone can benefit from an RV solar system.
There are a great number of RVers and campers that don't need any kind of RV solar set.
Solar power serves a single purpose - to charge your RV batteries.
(When your RV isn't plugged into shore power.)
In other words, it charges when your RV is off the electrical grid (off-grid).
Well, yes and no.
Technically every RV is "off-grid" a lot of the time.
Say, when driving down the road to your next destination.
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, but you aren't necessarily a candidate for solar power.
RVs with their own engine have one or more alternators that provide power to the RV house batteries (the batteries that power all the 12-volt systems in your rig).
Trailers (the vast majority of the time) have an 'umbilical cord' that charges from the tow vehicle while driving down the road.
If you always move your RV from campground to campground where you are plugged in, then you likely don't need an RV solar setup.
If you only occasionally camp 'off-grid' (dry camping) you might still not need a solar power system for RV use
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 the weekend, or a few days, you can head home, plug your RV in, and top off your batteries.
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.
We both boondock exclusively and are ALWAYS unplugged.
While this may change in the future, we still foresee ourselves as boondocking 99% of the time.
So we need RV solar panels to keep our batteries charged.
Otherwise we'd have to run the portable generator all the time, and who wants to listen to generator noise while camping in areas of 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 will be 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 RV 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.
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 your RV 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:
A portable solar system has its place in the RV world.
No question about it!
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 boondock but doesn't need a full-blown roof-mounted RV solar setup.
Portable RV Solar Pros and Cons:
If you don't think you are going to need much solar power, or you cannot justify installing roof-mounted RV solar panels, a portable system is a great option.
They also are a great way to expand an existing roof-mounted RV solar panel system (and give you a bit more flexibility as far as where you can park your RV).
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 RV solar panel, he opted to go with a portable 100-watt solar panel system that is 'ground deployed'.
A couple reasons:
- The sun in the winter is fairly low, and a flat roof-mounted RV solar panel doesn't provide as much solar energy production in the winter as it does 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 a very good thing (unless you've got a bunch of space and disposable money to put a lot of RV solar panels on your roof).
- The ability to park his travel trailer where he wanted without worrying too much about shading the roof-mounted RV solar panel is a good thing. There are times when the perfect shade tree appears and will provide relief from the harsh afternoon sun but will shade 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!
Camp Addict Co-Founder Kelly has used portable panels in the past without having a roof mounted RV solar system.
This RV solar setup served her well for a few years, even though it was a huge pain in her but to deal with two sets of ground deploy solar panels.
They usually were 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, followed shortly by a couple of lithium batteries.
Gone are her days of dealing with RV solar panels on the ground or worrying about if her power supply would last if there is a cloudy day or two in the forecast.
How Much Solar Power Do I Need For My RV?
The 10 million dollar question is 'how much solar power do I need for my RV'?
How many watts of solar power does an RV need in order to have enough solar energy coming in to both charge the RV batteries and be a power source for energy used during the day?
The short answer is: It depends. (So freaking annoying, right???)
Ask 100 people online how 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 some people are incredibly
How large should a solar system for RV use be?
There is no easy answer to this question.
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 RV's house battery bank.
Let us explain.
Lead-acid batteries (most commonly used for RVs) are rated to have a certain amp-hour capacity - that much is pretty common knowledge.
What ISN'T common knowledge is that batteries are rated at X amp-hour capacity at a certain temperature - normally about 77ºF (25ºC).
Any deviation from that temperature and you will have a battery will have a shorter life span (if too hot), or if temps are colder than the optimal temperature, you will have a lower usable amp-hour capacity (but battery life will increase).
Now you see why RVers love chasing the perfect 70º 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 what happens is that when you need battery capacity the most, i.e. when it's freezing outside and you need to 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 RV solar energy production capacity you might need is to go out and camp off-grid.
In other words, use your RV's 12-volt electrical system just as you normally would, but don't be plugged into shore power, a generator, or an RV solar system (assuming you have one).
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.
Figure Out Your Amp-Hour Consumption
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).
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.
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.
A battery bank consisting of two 12-volt batteries will be wired in parallel, while 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 (that we know is wired in parallel because of the above point), 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).
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 your batteries is where outside temperature comes into play.
Ideally, you will want to 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.
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 RV solar energy capacity you need.
With lead-acid batteries (the most common type used in RVs) you NEVER want to 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 RV batteries will love you for this and will reward you by having a long, healthy life.
Since a 100-watt RV 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 RV solar panel system.
Why would you want to buy more solar than you calculated you need?
If you have cloud coverage, your RV solar isn't going to produce anywhere near it's rated output.
So having an excess of solar energy producing capacity on cloudy days is a good thing.
Though, you probably will not have enough RV solar panels to make up for truly bad weather.
Marshall does not have this kind of excess solar energy production capability, so after a string of crappy solar days, it's time to pull out the portable generator.
Kelly is able to get by fine when faced with a couple of crappy solar production days with her 600-watts of RV solar panels on her roof, as well as her lithium batteries (it helps she doesn't use a lot of power overall per day).
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 a thing that you need to worry about.
If you are like the rest of us and live on planet Earth, you need to consider having excess RV solar energy capability.
This most likely means you will need a decent number of RV solar panels on the roof and might supplement 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.
You can later add RV solar panels to your roof should you find that your initial ground deploy solar panel purchase isn't enough (which most likely will be the case).
Polycrystalline or Monocrystalline Solar Panels?
RV solar panels comes with one of two types of solar cells:
The difference between polycrystalline (poly) and monocrystalline (mono) solar panel cells is how they are made.
Monocrystalline is more expensive but more efficient.
Poly solar panel cells are the cheaper of the two, are slightly less efficient than mono cells, and are made by many silicone crystals/fragments that are melted to form a larger 'wafer'.
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 mono cells have a distinctive square with cut-off corners appearance.
A poly solar cell system is somewhere in the neighborhood of 13-16% efficient.
A mono solar cell system runs in the range of 15-20% efficiency.
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 (in the case of roof mounted solar panels) 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 RV solar panels come with mono cells.
The cheap RV solar systems most likely come with poly cells, though as far as roof top 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 (weight is critical in many RVs) and roof space (also a major consideration for roof top setups) we recommend monocrystalline RV solar panels.
Solar Charge Controllers Explained
Solar charge controllers regulate the amount of voltage that gets transferred from the RV solar panels to the house batteries.
The charge controller will 'read' what voltage the batteries are at.
Then they will change the voltage that is 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) and MPPT (maximum power point tracking).
PWM controllers are less efficient, but are also cheaper than MPPT controllers.
PWM controllers are what come with portable panels, as well as most factory RV solar panel installations, so they will be what we concentrate on here.
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 (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 RV solar panels and reducing it to the level that the batteries will accept (without overcharging them).
Doing so 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 just cause your eyes to glaze over.)
When you are dealing with lower wattage systems, such as a typical portable setup, or most roof top factory installations, living with this inefficiency is a tradeoff to keep 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 and MPPT controllers are generally used (as the controller, while more expensive, will be a much smaller percentage of total system cost).
Solar Controller Charge Stages
A solar controller will have a certain number of charge stages, where a stage is the actual voltage that is being used to charge the RV batteries.
There are three basic stages (also known as a 3-stage charger):
- Bulk charge - 100% of available power from the RV 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 RVs batteryies 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 (each manufacturer is different) and hold this for the duration of the time sunlight is hitting the solar panels. This lower charge voltage will ensure 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 (and bring 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 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 (because 4 is better than 3, right?).
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 serves the purpose of making 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 (typically 10 - 12.1 volts which is a wide range, but again different manufacturers have different ideas and 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 will show 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 RV's 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.
Monitoring of 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
The solar charge controllers that come with portable solar panel kits are compatible with flooded, gel, and AGM style lead-acid batteries.
If you have lithium batteries in your RV (awesome deal if you do!) then you will 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 RV solar array that has an awesome MPPT solar controller if you've gone the lithium route, cuz you are probably somewhat of a power/solar geek.
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 RV's 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 RV solar energy production capacity you need to keep up with your power usage, then a battery monitor is a must-have accessory.
The Victron BMV-712 is a popular choice as it is relatively inexpensive.
It comes with Bluetooth capability that lets the monitor communicate with a smartphone app (both iOS and Android).
This way 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 that pictured below?
Because it doesn't keep track of the amperage used.
It only measures system voltage at the 12-volt outlet that you have it plugged into (measuring directly at the battery is far more accurate as there is no voltage drop due to the RV's wiring).
You need to use a TRUE battery monitor like the BMV-712 above to accurately track how much power (amp-hours) you use and therefore know how much solar capacity you should purchase.
Solar panels are a fantastic way to keep your RV powered and your batteries charged.
What you get will depend on your particular power usage and needs.
You should have a pretty good understanding now of the basic concepts of RV solar and the pros and cons of a portable setup versus roof top RV solar panels.
RV solar can be a game changer for many RVers, especially boondockers or people wanting to break their dependance from staying at RV parks.
Whether or not you think RV 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.
Kelly Beasley is co-founder of Camp Addict and loves sharing her enthusiasm for the RVing lifestyle. As a full-time RVer since May 2015, Kelly's playful writing style helps make learning about the sometimes dull subject of RV products a bit more interesting.
Camp Addict co-founder Marshall Wendler brings his technical expertise to help explain RV products in an easy to understand fashion. Full-time RVing since April 2014, Marshall loves sharing his knowledge of the RV lifestyle.