If you have an RV, one of the best ways to live off-grid and to always have a source of power is to install a solar photovoltaic (PV) system to cover all your electrical needs. This way you don’t need to constantly plan for a charging station and can be completely self-sufficient.
An off-grid solar PV system includes multiple components such as solar panels, inverter, charge controller, batteries, mounting hardware, protection devices, cables and wires. These can be complicated to interconnect if you don’t know how to do it. Lets go through the installation process that you must follow in order to properly and safely install your own PV system on the top of your RV.
Estimate Your Energy Needs
For RV’s one of the best ways to spare some time into selecting and matching equipment is to look for an RV solar kit that can match your energy needs. An RV solar kit will generally bring all the necessary components for the installation which becomes handy and useful. A practical and quick way to estimate what system size you need is to apply the following formula
Where the variables are:
- Ed : Energy demand per day
- Irr: Irradiance in the location in kWh/m2/day
- K: Derating Factor
- P: Power capacity needed in Watts
The best way to estimate your energy demand is to check all the devices and equipment that you want to back up with solar power and make a table showing the power consumption in watts (W) and multiplying it the amount of hours that each component is expected to be used on a general basis per day. This will result in watt-hours or energy demands, which by adding them up you will be able to get your full daily energy demand.
It is important to estimate your energy demand as accurately as possible since this can drastically change the PV system size that you would need to back up the loads of your RV. Remember that in this case the design is for an off-grid system, therefore annual demands are not as important as the maximum expected daily demands. Also, be careful with oversizing the energy demand too much as this can increase the system size unnecessarily and also the solar panel costs.
As an example let’s take for instance a daily energy demand of 3,500Wh in Colorado where the irradiance values can change anywhere between 4 and 7.3 kWh/m2/day. To get irradiance values from other locations you can check the solar resource map from NREL. Taking for instance an average irradiance of 5.5 kWh/m2/day we can estimate the number of watts needed. Also, the derating factor accounts for the typical losses in an off-grid system, which can be approximated to 0.6.
This means that to cover up that daily demand of 3,500Wh, you would need at least a 1061W system. Although, since it is rare to find solar panels to match these specific values, you would need to select a number of panels to size a system that can be close but higher than that value, in this case probably around 1.1kW – 1.2kW. Alternatively, you could also try to use the NREL tool for more accurate estimations, known as PVWatts, although for properly using it you would need to be more knowledgeable on this topic.
Now that you have your system size and after purchasing your ideal RV solar kit, the next step is to unpack it!
Get Your Setup Ready
Once you have received your solar RV kit, the first step is to check all the components to make sure they are all in perfect state. Your solar RV kit should include the panels, the mounting hardware, wires, and highly probable a charge controller as well. The battery and the inverter are generally not included, therefore these are components you need to select separately.
It is also sometimes recommended to include a tilt angle kit which allows to tilt the solar panels to a specific angle, which becomes useful to maximize energy production especially during the winter months. If desired, it is recommended to install this kit as well as the mounting brackets while on the ground. Also, setting up the layout on top of the RV making sure there are no leakages or damages to the roof before the installation.
Using the boxes where the panels came to resemble the size of the panels and to place them on top of the roof to visualize how the system would look is also a common practice. The layout for this must have previously been done, before purchasing the solar kit, to make sure that all the panels needed can fit into the RV roof. Guide yourself using this layout at the time to mount them.
In the process, it is recommendable that you use some protection equipment including gloves, glasses, and also use dielectric tools such as a dielectric screwdriver. Also, it is recommended to cover the solar panels during the installation to make sure they do not receive sunlight or artificial light. Besides, it is important to be careful while handling them and especially to beware of the MC4 terminals of the solar panels since even when not connected to any system, the solar panels have an open circuit voltage and they can generate an electrical current if the wires touch or connect to something. For further info, see our guide to wire sizing for solar systems.
However, at the moment, we can leave the solar panels down on the ground while we arrange the rest of the setup, they will be the last part of the system that we should mount and connect.
Install your Cable Entry Plate and Run Wires to the Charge Controller
The next step is to arrange the location where the charge controller, protection devices, and the batteries will be located. The charge controller and the batteries should be as close as possible to each other in order to reduce the voltage drop.
The setup for the charge controller is simple as it only needs to be mounted with screws and bolts. Now to shortest possible path from the solar panels to the charge controller should be considered as well to avoid voltage drop. The longer the wires and the thinner the gauge, the higher will be the voltage drop.
Generally the path selected follows one of these options. First option is the refrigerator vent, considered the most common as it avoids drilling holes. The second one is through the plumbing pipe. And finally the third option is to drill the roof of the RV to make the wires come through. The space behind the refrigerator can also be used in this case to run and secure the wires through the cabinets.
Now, in the case that you use the third option, you will need to use a cable entry plate. This is a device that allows to connect to the MC4 connectors of the solar panels and provides a waterproof entry to run the wires inside the RV. This is generally also covered with a sealant in all the borders of the cable entry plate to avoid any possible leaking.
After running all the PV wires down inside the RV, the next step is to connect the positive wire of the solar panels to the single-pole DC breaker which should be set into the off-position until the installation is completed. This device gives you control over when the PV system is providing power to the charge controller. This DC breaker should be installed in an easy to access location, ideally close to where the charge controller monitor would be located.
After the breaker, the positive (red) and negative (black) wires should be connected to the corresponding terminals in the charge controller. The wires are generally #12AWG or #10AWG size, but in any case keeping in mind the maximum gauge allowed by the charge controller is important at the time to select the wires.
Connect the Charge Controller and Battery Bank
Then, the positive output terminal of the charge controller must be connected to a battery fuse block through a high gauge cable that is to be the same gauge as the battery bank. The fuse (generally an ANL fuse) is to be installed ideally in the same compartment as the charge controller and the inverter while still being as close as possible to the batteries (although in another compartment) to prevent energy loss and voltage drop. The fuse should be sized to the nominal charge electrical current.
The battery temperature sensor can also be connected as well between the charge controller and the battery bank, this is important for temperature compensation charge.
On the other hand, the battery bank must previously be assembled and connected before interacting with the charge controller. The cables used to interconnect the batteries are generally large gauge cables (#4AWG and bigger). Gauge selection in this section is mainly driven by the ampacity needed to withstand the maximum charging electrical current.
The batteries same as the panels can be connected in series, parallel or series/parallel connections. The main goal is to reach the desired energy capacity required to back up the loads and to set a layout that provides the same system voltage as the inverter’s input voltage. The selection of the system voltage generally varies between 12V, 24V, and 48V in off-grid systems. The system voltage will vary depending on the size of the loads to be backed up, for higher loads a 48V system voltage would be required. This is to avoid excessive electrical currents.
Once your battery bank is set up, you must connect the positive battery cable to the previously installed ANL fuse.
Connect the battery inverter
After completing the previous setup the next step is to install the battery inverter ideally in the same location as the charge controller. The inverter’s job is to convert solar AC power to consumable DC power. The output voltage of the inverter for RV applications will generally be 120VAC or 240VAC depending on the loads that you are expecting to connect. The output of the inverter (AC side) will run 3 or 4 wires (depending on the AC system) which will be connected to the main electrical panel through an AC breaker. Meanwhile, the input of the inverter (DC side) will be connected directly to the battery bank, where the positive cable (red) will be connected as well to an ANL fuse sized to the maximum electrical load current of the inverter. The negative input terminal can be connected directly to the negative cable of the battery bank. Make sure that the inverter is set up in the off-position.
Install the Solar Panels
Then, the next step is to install the panels on the roof. Having all the rest of the system set up, it is time for making measurements and install the mounting brackets by drilling the roof. Properly waterproofing the installation with sealant and securing your panels is very important especially in RV’s since the panels will constantly be moving along with the vehicle. Once you have installed the tilt angle kit as well, it is time to attach the panels to the mounting brackets. Before doing so, it is recommended to cover the solar panels with the boxes that they came in to avoid any possible risk of electrical shock.
Once in place and attached to the roof, the panels can now be connected through the MC4 connectors in series or parallel according to the layout you have established before. All terminals will be connected except for the positive terminal from one side of the array and the negative terminal from the other side of the array. Later, by using an extension MC4 connector cable we can connect these two terminals and run them up to the point where the cable entry plate is installed and plug-in these extension to the device. It is important to make sure that there is no loose cable in any point of the installation.
Flip on the breakers!
Finally, the part that you were waiting on, remove the boxes that cover the panels, turn on the charge controller and the inverter, and finally flip on the DC breaker! Verify if everything is working properly and turn on some loads to test the system. And that’s it! Now you can take the RV out to a sunny camping site, set the dining table, tilt the panels and start enjoying solar power while living in the outdoors!
Frequently Asked Questions
It is important to ground your PV system as in the event of any failure there is a safe path for the fault current to circulate. To ground your PV system in an RV you can use the chassis as a reference point. Connect all the aluminum frames of the solar panels and run it down to the chassis where busbar terminals can be installed to make the connections of the grounding wires.
Make sure that the surface where the ground terminals will make contact are cleaned and free from oxide or paint. Then, the inverter and charge controller will also have grounding terminals for you to connect the green wire conductors. The grounding cables must be copper and they must be a minimum of #8AWG gauge conductor.
Flexible solar panels have great advantages. The first is that the weight of these panels is much lower than the rigid ones. Also, it is not necessary to drill holes on the roof to install them since they can be attached to the roof by using an Eterna Bond tape. A good brand like Sunpower, Renogy or HQST would provide high solar efficiency in these panels. However, their main disadvantage is that they need to be flat on the roof which reduces their energy production, especially on winter months.
Rigid panels weight is higher and is necessary to drill holes on the roof to install them, however, the tilt angle kit allows to adjust the tilt of the panels to reach a more optimum angle to increase solar power production. Could be said that if your priority is to maximize production, a good rigid solar panel with a tilt angle kit would be a better option, however, if drilling your roof is definitely not an option for you, then flexible solar panels might be a better approach.
Ultimately, there are several types of solar panel you can choose from for you RV solar installation.
Depending on the section of the RV system, a different type of wire should be used. For the section between the solar panels and the charge controller it is recommended to use the cables included with the modules and use MC4 extensions if needed. Alternatively, PV wires can also be used. For the section between the charge controller and the batteries it is recommended to use cable types THHN or THWN-2. Same can be applied to the section between the battery bank and the inverter.
To learn more about how to wire your off-grid solar system you can visit our article
Sign up now so you can get notified for our latest giveaways, discount promotions and guides