Best Solar Panels for RV, Motor Homes & Camping

Why a solar system on the RV?

A solar system can be a very useful add-on for the motorhome. Here are some of the advantages of a solar system:

• You are very self-sufficient because you do not have to rely on onshore power to recharge the batteries.
• Even away from camping and parking lots, a stay of several days is possible without having to recharge the batteries with an alternator.
• Owners of compressor refrigerators are practically dependent on a solar system if they are planning stationary stays lasting several days and do not have access to shore power. These refrigerators can only be powered electrically.
• For vehicles with Euro6 engines, charging the body batteries via alternator is not always possible without problems anyway. Instead of relying on a charging booster now, the task can also be taken over by a solar system.
• In particular, those who travels in sunny weather or in southern countries, can book a large gain in independence by a solar system.

For whom a solar system on the motorhome is not optimal

For those who mainly do winter camping or travel with their motorhome in Northern Europe, a solar system might not be a good solution: The flatter the angle of incidence of the sun’s rays in the North, the worse a solar system will work. This would then have to be compensated by a correspondingly large design of the system, or by a tracking system that always aligns the modules correctly to the sun. Whether the effort is worth it, you have to consider it carefully in advance.

Retrofitting a solar system on a motorhome

Retrofitting a solar system on a motorhome is easy. It is no problem to charge the motorhome batteries with several chargers, so you can simply connect your solar system additionally to your batteries. Solar panels are usually glued to the roof of the motorhome, or mounted on roof racks. Alternatively, a solar bag can be placed next to the RV if needed.

The questions you should ask yourself before retrofitting a solar system are:

• How much space do you have on the RV roof for solar panels?
• How much energy do you need on a daily basis (energy consumption of your appliances?).
• How much energy can you store? (Battery capacity?)
• Which solar components are suitable for you? (Comparison of requirements, space, price and performance)

What does a solar power system for a motor home consist of?

Solar systems for motorhomes are offered as a set, but can also be configured from individual parts. This is not particularly complex, there are not too many parts. However, the components should of course fit together.

• one or more solar modules
• a charge controller
• cables, mounting material

For roof mounting, a roof duct is also required. The system can be extended by a solar computer, which shows the performance of the system. A battery computer is also useful. You can read more about these components below. We do not consider the batteries, which are charged by the solar system, as part of the system. After all, they are already present in the vast majority of motorhomes anyway. Some solar systems also include an inverter (which then allows the operation of 230V devices), but this is also strictly speaking not part of the solar system.

Solar system for Camping considerations

Of course, you want to buy the best solar system, but how do you find it? What differences are there between the various offers at all? Well, basically all solar systems produce electricity. The difference lies primarily in the extent to which they do so in low light conditions. Opinions are divided as to which systems are most effective in meeting these challenges.

Basically, however, the following factors have an influence on the performance of the solar system:

• quality and design of the solar modules (cells used, quality of the module structure, bypass diodes, etc.).
• type and quality of the solar charger
• selected circuit and voltage
• outside temperature and solar radiation

Better solar modules and better solar chargers promise a higher yield. However, the extra cost can be so high that if the components are inexpensive, you might as well just buy double the number. Especially if you have a lot of space on your RV roof, for example, two inexpensive solar modules will always yield more than a single expensive module with the best technology. Especially inconvenient for solar panels is the fact that solar cells work worse and worse the warmer it gets. On the other hand, more solar radiation is needed for a good yield – which unfortunately leads to warming again.

Solar modules/solar panels for RV

Solar modules (often called solar panels) are photovoltaic generators that are used to produce electricity from solar energy. Mostly, solar panels are mounted on the roof of the motorhome, where they can do their work. Alternatively, so-called folding modules or solar cases are also possible, which are placed next to the motorhome (or behind the windshield) only when needed.

Solar modules for motorhome use are usually supplied pre-fabricated with so-called MC4 connectors, with which they can be connected to the charge controller without tools – provided that a suitable cable is available. The connectors also make it easier to reconnect or temporarily remove the solar modules at a later date.

The solar cells

Solar modules consist of solar cells that are interconnected. By interconnecting a sufficient number of solar cells, the desired voltages are achieved.

• State of the art is so-called monocrystalline modules.
• Polycrystalline solar modules have lower efficiency and are more susceptible to partial shading, but are cheaper to obtain.

However, if you are looking for solar panels for your RV, you will be offered primarily monocrystalline modules.

Selecting solar panels for motorhome

Solar panels now differ in

• size
• yield
• voltage
• susceptibility to partial shading and performance in low light conditions
• construction (flexible or rigid)

In the triangle of energy demand, available space for the solar modules, and budget, you now have to find the right variant for you.

• which appliances do you use
• how long per day a day.

Then look up in datasheets how much power they consume in watts.
Watts divided by volts gives the amperage (Ampère A):
W/V = A.
A multiplied by the duration in hours gives Ah.

For example, a 10W LED light will draw (10W/12V) 0.83A. If you need this LED light for 2 hours a day, you will consume 1.6Ah.

Don’t forget with your calculation on:

• light
• water pump (for the sink, shower, and toilet),
• chargers (laptop, camera, smartphones)
• heating (especially diesel heaters need a lot of power)
• refrigerator (especially if you have a compressor refrigerator).

Once you’ve summed up the average daily consumption of your devices, the next thing to do is make sure your battery capacity matches it.

Know your battery capacity in the motorhome

If you have a 100Ah body battery in the motorhome, it depends first of all on the battery type, how much of it is available to you at all. A normal lead-acid/gel or AGM battery should only be discharged to half its capacity. Anything more than that is at the expense of the battery’s service life. Therefore, with 100Ah, you actually only have 50Ah of energy available. This is different from the modern LiFePo4 battery, which you can discharge almost completely. These batteries are (still) very expensive, but they are light and much more suitable as a body battery. In the motorhome, however, they are not yet very common.

If you have 50Ah available (i.e. you have an ordinary 100Ah battery or a 50Ah LiFePo4 battery), then that’s the amount of energy you can use without recharging until you are, so to speak, running on empty.

Now there are two cases:

• your daily consumption exceeds your usable battery capacity: then you need a bigger one or another battery.
• your daily consumption is below your usable battery capacity. Then you can think about how to replace the consumed energy.

If your battery capacity is only just sufficient in case 2, you should still think about expanding the battery capacity. After all, what do you do if it rains all day and your solar system doesn’t work? The higher your usable battery capacity is compared to your daily consumption, the longer periods of time you can bridge. In our example, let’s assume that we consume 30Ah per day. This means that our goal should be to be able to recharge 30Ah with the solar system every day. A little more certainly won’t hurt, e.g. to compensate for temporarily higher consumption and to have excess capacity for bad weather. However, completely oversizing the solar system will not do any good, because the energy cannot be stored anywhere if the battery is already full.

Solar modules/solar panels for RV

Solar modules (often called solar panels) are photovoltaic generators that are used to produce electricity from solar energy. Most solar panels are mounted on the roof of the motorhome and can do their work there. Alternatively, so-called folding modules or solar cases are also possible, which are placed next to the motorhome (or behind the windshield) only when needed. Solar modules for motorhome use are usually supplied pre-fabricated with so-called MC4 connectors, with which they can be connected to the charge controller without tools – provided that a corresponding cable is available. The connectors also make it easier to reconnect or temporarily remove the solar modules at a later date.

The solar cells

Solar modules consist of solar cells that are interconnected. By interconnecting a sufficient number of solar cells, the desired voltages are achieved. State of the art are so-called monocrystalline modules. Polycrystalline solar modules have lower efficiency and are more susceptible to partial shading, but are cheaper to obtain. However, if you are looking for solar panels for your RV, you will be offered primarily monocrystalline modules.

Selecting solar panels for motorhome

Solar panels now differ in:

• size
• yield
• voltage
• susceptibility to partial shading and performance in low light conditions
• construction (flexible or rigid)

In the triangle of energy demand, available space for the solar modules, and budget, you now have to find the right variant for you.

The size of the solar modules

The size of the solar panels directly affects the yield: larger panels can provide more energy because they consist of a larger number of solar cells. However, for roof mounting, you need to make sure that the solar panel will fit on your roof. Therefore, calculate the space you have available and be sure to consider obstacles (such as chimneys, skylights, roof racks). In addition, there are solar cells with higher efficiency and those with lower efficiency. More efficient cells also result in solar panels that are smaller in size than those that are lower inefficiency (for the same power output). Calculate your power requirements to know the minimum power needed! Keep in mind, however, that performance decreases in low light. Our tip: If you have the space, choose a larger size than necessary.

The weight of the solar panels

For RVs that have notorious weight problems, the weight of solar panels is of course relevant. If you really want to save weight, you have to choose flexible solar modules.

A flexible 100W solar module weighs about 4.4 lbs.
Rigid solar modules, on the other hand, weigh about 13-22 lbs for an output of 100W. This is mainly due to the weight of the metal frame around the module, as well as the glass plate above it. However, the weight also depends on the technologies used.
Partial shading

Causes of partial shading include

• trees/branches on the pitch,
• roof boxes
• surfboards on the roof
• satellite dishes
• chimneys
• roof railing spars.

Try to minimize the likelihood of partial shading from these causes as much as possible during installation by choosing a suitable location for mounting the solar modules!

Heat and solar: rear ventilation

The warmer a solar cell gets, the worse it works. For this reason, it is often recommended to ensure sufficient rear ventilation of the solar cells: This means fixing them in such a way that air can pass by on all sides. This is hardly possible with flexible solar modules, which are glued to the roof. It is true that you can find variants in motorhome forums where flexible modules have been mounted on a specially manufactured aluminum carrier. However, it is doubtful whether this still leads to a large weight saving.

Circuit of the solar panels: Serial/in series or parallel

If there are several solar panels, there are two possibilities of connection

• In series: a cable goes from one panel to the next. The positive pole of one panel is connected to the negative pole of the next panel. The positive pole of the charger is connected to one panel, the negative pole to another. The voltages of the solar panels are added, the current remains the same.
• Parallel: each panel is connected to the charger with positive and negative poles. In other words, the plus poles of the panels are connected to each other and to the charger. The same applies to the negative poles. The currents of the solar panels add up, the voltage remains the same.

This means that the choice of connection increases either the current or the voltage. This is relevant because now the charge controller has a certain range in which it works ideally: If the input voltage is too low, it cannot charge the batteries. So with the circuit, you can bring the whole system into a range that is ideal for the charge controller. Only modules with the same WP specification can be connected in parallel.

Conclusion

As you can see, there is a lot to learn, but actually the topic “solar system in the motor home” is not that complicated. With the knowledge from this article, you can calculate the demand and design of your solar system better than the dealer (who unfortunately usually does not make this effort). For critical installation tasks (secured, sufficient wiring and connection to the battery) you should use specialized companies if you do not have the necessary skills yourself. Then nothing stands in the way of a self-sufficient motorhome trip with its own power supply!