What Size Solar Power System Do I Need For My RV?

So, you’ve gone and bought a recreational vehicle. A nomadic life in the great outdoors awaits.

However, you may now be thinking: What size solar power system do I need for my RV?

To work out how much solar power you need, it’s vital to know two things: How much power you use, and how much power different solar batteries store.

The two main components of the basic power equation are this:

• Power used: The amount of amp-hours you will use each day, on average.
• Power stored: The amount of energy your solar panels provide to your battery.

As you can see, how you balance the equation totally depends on the size, make, and model of your RV, as well as how much power you plan to use. 

The following article will break down all the factors that affect power consumption, and how to use these to calculate exactly what size solar power system you and your RV will need.

Why Install a Solar Power System in your RV?

Like anything in life, installing a solar power system in your RV has its own set of pros and cons. The lists below explore both sides of harnessing solar energy to power your RV.

Advantages

• Solar systems are free to recharge. The sun doesn’t cost a thing. For those using their RV in high light environments, you’ll never have to worry about your next charging opportunity- as it will already be happening.
• Long term financial gains for serious campers. Setting up a solar power system for your RV is a serious investment, but for those who plan to live in their RV full-time (or close to it) your system will pay for itself in fuel savings in roughly two years.
• Absolute freedom of camping. You’ll no longer need to plan for close proximity to gas stations when picking your next camping ground, nor to pay any attention to the nearest campsite. With a solar powered RV and good weather, you can go wherever the wind takes you.
• Good for your battery. Solar systems keep RV batteries healthy and charged above 50%. If charge drops below this level, it can significantly impact your battery lifespan by shortening it severely. As solar panels consistently charge your battery, it is highly unlikely this will occur.

Disadvantages

• You won’t see a return on your investment anytime soon. Unless you’re the type of camper who is practically living in their RV, the cost of materials and installation is not going to be cancelled out by subsequent fuel savings. Only install a solar power system for an RV if you are going to be using it heavily, in sun-rich areas.
• You become totally dependent on the weather. Solar panels do still operate under cloud cover, but their efficiency is reduced enormously. This can be as much as 75-90%, depending on the severity of said cloud cover. Now, if you are in a sun-rich state, this is no problem. However, for everyone else, consider this point carefully before installing a solar power system for your RV.
• Solar power is inefficient compared to alternatives such as generators, vehicle alternators, or even shore power. To power amenities such as air conditioning, solar panels will struggle. Therefore, if you know for certain that your power usage is high and that you love to use high-energy-expenditure appliances, solar power is probably not your best bet.

What are the Major Parts of a Solar Power System Set Up?

Here are the main elements of a solar power system:

• Solar panels: Solar panels are photovoltaic components that harness sunlight so that it can then be turned into electricity.

• Charge Controller (MPPT/PWM): Solar charge controllers limit the speed (or rate) at which electric current is sent to or taken from batteries.
  
  They provide insurance against overcharging, overvoltage, and overall electric overload. These may be subcategorized further:
  • MPPT: Standing for Maximum Power Point Tracker, these charge controllers operate by optimizing the voltage and current for maximum power output from your battery.
  • PWM: Standing for Pulse Width Modulation, these charge controllers are best conceptualised as a power switch between the battery and the solar panels. The switch is turned on and off as needed to keep the voltage of the battery at what is called “absorption voltage”.

• Battery(Lithium-ion/AGM/Lead Acid):Charging batteries is the most common method of storing power. There are three types of batteries that will be defined here:
  • Lithium-ion: These types of batteries are composed of cells through which Lithium ions move via an electrolyte. The ions move from positive to negative electrode during power discharge- and then back the other way, when the battery is being charged.
  • AGM: Short for Absorbent Glass Matt, these batteries are a more advanced form of the classic Lead Acid battery listed below.  AGM batteries are renowned for being resistant to vibration (like that which is caused by a moving RV) and non-spillable.
  • Lead Acid: Lead acid batteries are the earliest type of rechargeable battery ever created.  When compared with other, more advanced types of battery, these Lead Acid models have a rather low energy density.

• Inverter (Pure Sine Wave Inverter):  To convert direct current (DC) into alternating current (AC), a pure sine wave inverter is essential. The charge is converted from DC into AC by becoming a pure sine wave output.

How to Size your RV to Determine Power Required

As stated above, the basic power equation that needs to be balanced for you to work out your RV power needs is as follows:

• Power used: The amount of amp-hours you will use each day, on average.
• Power stored: The amount of energy your solar panels provide to your battery.

To begin balancing this equation, there are a couple of factors to consider.

Identify All Appliances

It’s vital to identify all appliances in your RV, and to establish how long and how often you will be using them. 

Figure out the exact total of amp hours, and amps, of your average daily energy expenditure.

Go on a Camping Trip

The next thing for you to find out is the average amount of sun hours at your desired location. 

This can be achieved most accurately by going on a camping trip, and recording the data yourself. 

Once you have this information, you can calculate how much power x amount of sunlight will provide. From here, you can then determine what size battery you need to service your energy requirements.

How Many Solar Panels do I Need for my RV?

Now that you’ve identified the power required, you will be able to calculate how many solar panels your RV will need in order to be able to harness the power from the sun.

One rule of thumb that every RV camper should remember is this: A 100 watt solar panel will produce 800 watt-hours of energy if exposed to direct sunlight for eight hours in a day.  

However, it’s perhaps more practical to think about it in this way: Accounting for variable cloud cover and other weather discrepancies, a 100-watt solar panel will produce around 30 amp-hours of energy in total. This amounts to 350 watt-hours.

Keeping these in mind, take your daily energy requirements (in watt-hours) and divide it by 350, and you should have an idea of the number of 100-watt solar panels that you’ll need.

Below is a summary of rough panel requirements per appliance used. These may differ depending on your overall needs.

• 1-2 berth: 115 watts and above, for the bare minimum. I.e. Lights, and a fridge.
• 3-4 berth: 175 watts and above, which would support lights, refrigerators, and small inverters.
• 5-6 berth: 300 watt and above, for anything more than what has already been listed above.

Something else to consider as well is your roof space. It’s very important to tailor your energy needs to the physical dimensions of your TV, so that you know for certain you can generate the necessary power.

Solar Panel Types

Monocrystalline vs Polycrystalline are the two main types of solar panel. Their features are:

• Monocrystalline: Solar panels that contain monocrystalline cells are formed of an ingot of high-purity silicone. Monocrystalline is cylindrical in shape, which is sliced into wafer-like shapes that are called cells.
• Polycrystalline: Polycrystalline panels consist of several silicone crystals. Like their monocrystalline counterparts, the cells are of high-purity silicone. The silicone fragments are melted together to create the panel cells.

Permanent or Portable Solar Panels?

Portable system

Pros

• Flexible: With a portable system, you’re not limited by the roof space of your RV. Instead, you’ll be able to set up your solar panel system on the ground at your campsite.
• Efficiency: A portable system can gather sunlight even while your RV is parked in a shady spot, due to the fact that they are not attached to the vehicle.

Con

• Time and labor intensive. Portable systems must be set up and dismantled after each use, so they are not for those who want to keep things simple.

Permanent system

Pros

• Requires no further setup beyond installation. You won’t have to worry about having to set anything up- once you’re parked, that’s it.

Cons

• The RV has to be parked in a way that maximises its exposure to direct sunlight. This can sometimes be difficult, and can also increase the heat within your RV. Increased heat can lead to increased power usage too, which definitely isn’t ideal.

Charge Controller

When deciding on a charge controller, it’s essential to opt for the MPPT rather than the PWM. 

This is because the MPPT offers greater voltage optimization, which will increase the longevity of your battery. 

Whereas, PWM charge controllers do the bare minimum, and this will take a significant toll on your batteries.

Batteries

When it comes to RV batteries, Lithium-ion batteries are the best option. 

They are easy to store, being at least 25% lighter and smaller than any comparable lead acid battery. They are rapidly charged, reducing wait times and increasing camping efficiency.

They are between four and six times less expensive per kWh than their competitors, and have incredibly long lives. 

They’ll last for at least 5000 cycles, even if your power discharge rate is between 80-100%.

Solar Inverters

Do I need an Inverter for my RV?

Yes. An inverter is essential to convert direct current to alternating current, as this is the type of current that powers electrical appliances.

Inverter size

The quickest and easiest way to decide what size inverter your RV requires is to add together the absolute largest amount of watts you think you’ll use at a given time- and then add 20%.

The resulting number, in watts, is the minimum size of inverter that you’ll need.

DIY or Professionally-Installed Solar Power System in your RV?

Unless you’re an experienced mechanic and/or electrician, it’s definitely best that you let the professionals handle the setup of the solar power system in your RV. 

With professionals, you can rest assured that there will be no errors that would otherwise result in electrical inefficiency and subsequent loss of power.

However, solar panel system installation can be done on a DIY basis if you are confident in your knowledge and skill.

For a fuller explanation of the dos and don’ts of DIY RV solar panel setup, please consult this page.

Conclusion

In conclusion, setting up a solar panel system for your RV is no mean feat. You’ve seen for yourself in this article just how many things an RV solar power system setup depends on.

There are a multitude of factors to consider, but once you have balanced the power equation, run some camping tests, and weighed up all the options, you’ll be able to determine whether solar power is the right way to power your RV.

If so, you’ll also know exactly the number of panels and size of inverter that you’ll need. All the best for your upcoming RV adventures.