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DIY: How to install solar panels on your RV
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DIY: How to install solar panels on your RV

25 mins 09 Mar 2021
So, you've decided to try solar energy for your RV? Good choice. Unlike generators, solar panels are silent and smell-free, they barely need any maintenance and pay for themselves in several years. In this article we'll guide you through the installation process of all the necessary parts of an RV solar panel system: panels, a charge controller, and an inverter.

Fix panels with screws or adhesives

Before installation, make sure you've figured out where exactly you're going to put panels on the roof. Make and check all the necessary measurements. Keep in mind that in the USA solar panels produce the most energy when facing south at an angle between 30 and 45 degrees. Panels better not be overshadowed.

Solar panels are typically attached to the roof with screws or adhesives. The way you'll do it depends not only on your personal preference, but also on the type of panels you've chosen, shape of your RV's roof and its material. Of course, nobody forces you perform the installation yourself – call for professional help if you feel you need to.

Flexible thin-film panels are typically attached to the roof with an adhesive. However, it is better when there is some empty space between a panel and the roof – ideally 6 inches. Panels heat up under the sun, which lowers their efficiency and contributes to heating up the whole vehicle in summer. If air can circulate underneath, it naturally cools panels down.

Rigid polycrystalline or monocrystalline panels usually rest on mounting brackets, which require drilling. Here are some popular options:
Mounting Z brackets

Among the cheapest options: you can get a set of 4 brackets for $10

Usually require drilling, though it's possible to use adhesives

Don't allow to adjust the angle of panels
Tiltable mounting brackets or mounting frames

Cost between $30-$50

Usually require drilling

Allow you to easily adjust the angle of your panels.
Corner brackets

a set of four brackets for one panel is going to cost you 20$-40$

don't require drilling

don't allow to adjust the angle of panels

suitable for any panels with aluminium frame
While these examples show the most popular ways of mounting solar panels on an RV, they do not exhaust the list. Some RV owners even make brackets and mounting frames themselves. However, if you don't feel like doing any DIY, never mind – commercial options aren't that expensive.

If you opt for a drilling option with mounting brackets, put some sealant under each bracket not to let the water into your RV. Make sure that the sealant is compatible with the material of your roof.

Before you ask, yes, you can drill into the side of a solar panel. All the wiring is inside a panel itself, and aluminium is like a picture frame. However, be careful with the angle you are drilling at – don't harm the cells.

Put a charge controller in plain sight

Charge controller is a safety measure for your house battery, but it also lets you monitor the state of your RV solar panel installation. You should put it close to the battery, but make it visible – you'll need to check it from time to time.

The most basic models of controllers tell you the load of the battery, its state and the voltage of panels. More advanced ones measure the temperature, let you specify the charging time and more. Some models can be connected to your smartphone via Bluetooth and managed this way.

A charge controller comes with a user manual where you can find the wiring diagram for it. Normally, a charge controller is first connected to the battery and then to the panels. Just don't connect your solar panels directly to your RV battery – it might overheat and explode from high voltage of panels.

Connect a charge controller and a battery

Wiring together a controller and battery is simple and can be summarized in three steps:

1. Use a stranded copper wire to connect the two.

2. Black wire goes from negative terminal of a battery to negative terminal of a controller. Red wire connects two positives. If two wires are the same in color, use red velcro tape to mark the positive cable.

3. Turn on the charge controller. It should now be able to measure the load of a battery.

Use the fridge vent for wires

Now we need to connect the charge controller with solar panels and here's the problem: how do we get wires to the roof? There are several ways you can set up the RV solar wiring:

Fridge vent

Fridge vent

This is the most common way to wire solar panels on top of the roof with a charge controller inside an RV.

Existing or custom holes

Existing or custom holes

When a refrigerator vent isn't available, try searching for any other holes in the roof you may have made earlier. If there are none, you can drill new ones. Make sure you can easily access them from the inside of your RV. After wiring, add some sealant to prevent leaks.

Ideally, wires between all the components of a RV solar panel system should be as short as possible to minimize power losses. You can also use thicker cables for that purpose, but they are expensive, hard to fit and weigh more.

Connect panels: series for voltage, parallel for amps

With one panel you just plug its positive and negative cables into the corresponding sections of a charge controller. Cables that come out of the solar panel's junction box often have MC4 connectors, which means that you might need a corresponding pair. "Female" connector marks a positive cable and "male" is for a negative one.

If you have several solar panels, wiring them with a charge controller becomes less straightforward. Basically, there are three options.

1. Series connection

1. Series connection

This way the negative cable of one panel goes to the positive of the second one, the negative of the second goes to the positive of the third and so on. Eventually two unused cables from the first and the last panels go into the charge controller.

Wiring in series means amperage of panels stays the same, but their voltages are combined. An MPPT-controller can convert this high voltage into additional current for the battery. This connection works well when a charge controller and panels are far apart. The downside is vulnerability of the system: if a cable breaks somewhere or one panel malfunctions, the whole system suffers. If one panel is under the shade, it decreases the performance of the whole array.

2. Parallel connection

2. Parallel connection

In this case positive and negative cables often go into a combiner box. A combiner box makes one thick positive cable out of, say, three positive cables from three panels, and one negative cable out of all the negative cables. This pair then goes to the charge controller. Sometimes MC4 branch connectors are used instead of a combiner box.

Wiring in parallel means the voltage of panels stays the same, but their amperages combine. If one panel stops working, it doesn't affect the others. However, high amperage means you need really thick cables. This type of connection is used for tight spaces, like an RV. Wiring in parallel goes along well with a PWM-controller since voltage stays low, but requires a combiner box or MC4 branch connectors.

3. Series-parallel connection

3. Series-parallel connection

Is usually used with a large number of panels. It's a combination of the two other wiring methods, which allows you to adjust the voltage and amps of your solar array to the properties of your charge controller. For example, you can create two strings of panels with high voltage, but then wire them in parallel to combine their amperage.

Add inverter to power RV appliances

Not every RV solar panel system needs an inverter, but if you want to use solar power for things like a laptop or a blender, you'll need alternating current (AC). RV inverter installation is simple: you attach it to the terminals of your house battery with large battery cables.

For safety reasons, it is recommended to add a fuse or circuit breaker between an inverter and a battery. Some inverters already have a built-in fuse, so consult the manual for your inverter for more details. Usually the manual also contains recommendations on wire size and fuse rating. Ask for advice from electricians if you are feeling unsure.

Preferably, you need to place an inverter near a battery. At the same time, an inverter is internally complex and fragile, which means it needs a cool place out of direct sunlight. All the electrical appliances that require 110V AC can be plugged into the inverter directly, but a surge protector will be more convenient.
Illustrations – Marina Fionova
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