Solar panels atop RVs are all the rage. Everybody’s installing them. But what are RV solar panels? How do they work, what can they do for you, and are they worth the investment? Let’s find out!
What Are RV Solar Panels?
In the 1800s, scientists observed something called the photovoltaic effect, where some materials would produce an electric charge and current when exposed to sunlight. Attempts were made over the years to create “solar engines,” as they called them, but most had very low efficiencies. It wasn’t until the 1950’s that scientists discovered that silicon (found in sand) could create a much more efficient solar panel.
This initial discovery led to the development of solar cells that could harness the sun’s energy and turn it into electricity. The technology has evolved over the years, but the concept remains the same.
A solar panel is a panel filled with solar cells that capture the sun’s energy and turn that energy into usable electricity that powers homes, businesses, coffee pots, and, yes – your RV!
Let’s find out how it all works!
How Do RV Solar Panels Work?
Let’s imagine you have a couple of solar panels on the roof of your RV. If your RV is on the road or parked during the day, sunlight hits your solar panels, and cells on the panels absorb energy from the sun.
Within your solar panels’ cells, circuits take the energy absorbed by the sun’s cells and turn it into electrical current. The electrical current is fed through wires to a charge controller that controls the battery’s current.
So the system looks like this:
This energy becomes DC (direct current) electricity that charges your RV’s house battery or batteries, essentially “storing” energy to be used to power devices and appliances in your RV or charge devices for your later use.
This DC power from the solar panels and batteries is typically 12 volts. This DC power runs lights, appliances, and electronics in the RV.
However, you can also take that 12-Volt DC, pass it through an inverter, and convert it to 120-Volt AC (alternating current) electricity (like the outlets found in a sticks-and-bricks house) to power 120-Volt devices such as a coffee pot.
There are 120-Volt outlets scattered throughout your RV, but those don’t have power unless you’re using a generator or your RV is plugged into shore power.
If you want to run a 120-Volt appliance when you’re boondocking in the desert, you can harness the sun’s energy through solar panels —> charge controller —> batteries —> inverter, and voila! = 120-Volt electricity at your command!
Theoretically, you can power anything with the sun’s energy provided you have enough solar panels, batteries, and conversion ability!
How To Know How Many Solar Panels You Need For Your RV
Knowing how much solar power you need for your camping comfort involves figuring out a couple of pieces of information. These two parts of the equation help you determine how many solar panels you’ll need for the sun’s power to deliver the electricity you want. The two parts of this equation are:
- How many watt-hours will you use each day? (energy used)
- How much energy do your solar panels provide to your battery/batteries? (energy stored)
You must balance all of this for an optimal system. Solar panels without enough batteries to store all of the power they produce will waste your money and not provide the power you need.
Conversely, one solar panel and lots of batteries will not allow enough of the sun’s energy to be harnessed to fill those batteries for your use!
Figuring out this balancing act can take some work and requires an entire article of its own to explain, but we can distill down the basics here.
Calculating How Much Energy You Use
First, you need to know how much energy you use in a day. There are a couple of ways you can do this. The first involves math. Estimate how much power you’ll consume while boondocking in your RV by learning what each device or appliance you want to use consumes and multiplying that by the number of hours you’ll use that device or appliance.
Here’s an example: You have one television that consumes 90 Watts. You estimate that you’ll watch television for approximately two hours per day. So 90W x 2h = 180 Watt/Hours per day
You can do the same for every appliance or device you may want to power as you boondock, and you would add the total of Watt-hours consumed. From there, you can estimate how many panels you need.
Calculating Energy Generation and Storage Needs
A decent assumption is that a 100-Watt solar panel will generate on average 350 Watt-hours of power per day. However, this will vary significantly by location and time of year. This article by Mortons on the Move explains a way to get a more accurate result by using PVwatts.
You’ll also need to know how many batteries you’ll need to store that amount of power! One 100 ah 12volt Battle Born battery has about 1200 Watt-hours storage capacity.
Keep in mind that your solar panels will only give you the stated number of Watts under perfect conditions. Perfect conditions = direct sun pointing directly at the panel. On a rainy day, you won’t get 100 Watts from your 100-Watt solar panel. If you’re parking in the shade, you won’t get 200 Watts from your 200-Watt solar panel.
It’s also challenging to estimate the amount of power you’ll use on a given day because days are different. You may be outside all day today enjoying nature, and fall into bed and watch 15 minutes of television tonight. Tomorrow could be a rainy day, and you’ll stay inside your RV, do a lot of work on your laptop, and watch a couple of hours of television in the evening. So estimating high is usually a good idea!
Rather than estimating your daily power consumption using math, some people prefer to simply go out camping without electrical hookups and monitor their battery usage over a typical day. Installing a battery meter like the Victron BMV712 before installing solar can give you an accurate reading of how much power your RV needs.
RV Solar System Components
Before we take a look at how you install a solar system, let’s review the RV solar system components:
Your battery bank is the heart of an RV’s power system. Without a battery, an RV has no way to store power. The battery is where energy provided by the sun is stored for your use. Your solar panels will charge the battery bank.
But not all battery banks are created equal, and not all are suited to the unpredictable charge cycles of solar systems. Lithium batteries for solar applications are the superior choice over lead-acid.
Read The Truth About Lead-Acid Vs. Lithium-ion Batteries to understand the differences.
RV Solar Panels
Your RV solar panels will sit on the roof of your RV collecting energy from the sun in the solar cells and transferring that energy (through a charge controller) to your battery bank. Your solar panels may lay flat, or you may choose to employ a mounting method that allows you to angle the solar panels toward the sun.
The charge controller mounts inside the RV. Wires run from your solar panels to the charge controller and from the charge controller into your battery bank. The purpose of the charge controller is to control the rate at which your batteries charge. The charge controller is required to prevent overcharging and in the case of an MPPT charge controller, operate the panels as efficiently as possible.
The electricity from your batteries is 12-Volt DC electricity. With this, you can power all 12-Volt devices and appliances as well as the 12-Volt (cigarette lighter) ports in your RV. If you want to use 120-Volt AC electricity to power a coffee maker, laptop, Instapot, or anything that requires AC, you’ll need an inverter that transforms 12V DC power to 120V AC power.
You’ll mount your inverter inside your RV as close to your battery bank as possible, and your AC appliances and devices will receive the transformed (from DC to AC) power from that inverter.
Do You Need To Use RV-specific Solar Panels?
No! Any type of solar panel can be made to work with an RV; however, there may be some challenges.
First is space available. An RV roof may have lots of stuff on it and require the use of smaller panels. If the roof is wide open, full-size residential panels like used on homes can be used for RV solar panels.
The second challenge with non-RV-specific panels is the voltage they operate at. Most RV solar panels are around 17-20 volts which will work with most PWM charge controllers to charge a 12-volt system. Home solar panels are usually 40-70 volts and cannot be used with PWM charge controllers.
You can use MPPT style controllers as long as they have a high enough voltage rating. Using an MPPT controller allows the use of most of any solar panel for an RV.
How To Hook Up Solar Panels to RV Batteries
Now that we know how many solar panels you want to add to your RV let’s figure out how to connect them to your RV batteries to produce the electricity you need!
Solar electric systems for RV’s vary enormously, especially if installing a larger system is sure you are confident working with electrical wiring before taking this on. For systems up to a few hundred watts or kits, the voltages are not dangerous and can be installed by anyone. Regardless of the size, the following instructions are a high level of how the components should be wired.
Let’s assume that you’ve purchased a kit containing the solar panel system parts, and you have a battery or battery bank installed in your RV.
Your kit will contain:
- A solar panel (or more than one, depending on what you’ve opted to buy).
- A charge controller.
- A wiring harness (and possibly connectors, adapters, and mounting brackets)
You may also want a battery monitor and an inverter (to turn that 12V DC power into 120V AC power).
Steps for Connecting RV Solar Panels to Your RV Batteries
Here are the steps to connecting your solar panels to your batteries:
- Mount your solar panels on the roof of your RV.
- Mount your charge controller inside the RV as close to your batteries as possible.
- Run your wiring from the solar panels into the RV and over to the charge controller. (You can run your wiring through a refrigerator vent or through the holes where the plumbing enters the RV if these are located near your batteries. If not, you can drill a hole through the roof of your RV to run your wires and thoroughly cover and caulk any drilled holes.) You should install a fuse or circuit breaker on the wires for this run.
- Connect the wires from your charge controller to your battery bank. A fuse slightly larger than the charge controller’s rated current should be installed on these wires.
- At this point, the system is fully installed but the RV solar panels are not connected to the charge controller. Before making the final connection it’s important to double-check all wiring to make sure polarity (positive and negative) are all correct. Once confident you can plug in the solar panels to the charge controller. We recommend doing this at night or with the solar panels covered by a blanket to prevent a spark.
- This step is optional, but if you want to use 120-Volt AC appliances, you’ll want to mount an inverter inside your RV, as close to the batteries as possible, and run appropriate wiring to that inverter.
Note: If you are wiring your solar panels/controller directly to your battery bank, there is no need to disconnect the existing converter in your RV. Both the converter and the solar panels will be able to supply charge to the battery bank.
Are RV Solar Panels Worth It?
If you always camp at campgrounds and RV resorts where you will be paying for electrical hookups to power your RV and your various devices and appliances, then investing in a solar system may not be worthwhile.
However, if you like to boondock – to stay in areas where there are no electrical hookups – beaches, city parks, state parks, the desert, a solar panel system is an excellent addition to your RV lifestyle. Solar panels provide silent power and can minimize the need for a noisy generator to recharge your batteries.
Solar panels are a remarkable development in renewable energy! As an RVer, a solar panel system frees you! It allows you to go anywhere and stay anywhere, harnessing the incredible power of the sun to address all of your electrical needs.
Want To Learn More About Electrical Systems and Lithium Batteries?
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