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If you own an RV or campervan, you've probably considered investing in solar panels for your vehicle. Before you start shopping around for solar panels for your RV, it's important to understand the basics behind them, including what they're used for, how to install them and how many of them you need, Let’s find out the answers.
Unlike residential and commercial solar systems, which are designed to power an entire home or business, RV solar systems typically deliver a more modest output. This usually isn't an issue since you don't use as many lights and appliances in your RV as you would in a big house.
So how many solar panels will you need for an RV? It depends on a few factors, including
1. How many watt-hours will you use each day. (energy used)
2. The Electrical System of your RV. (12V, 24V or 48V)
3. How much energy do your solar panels provide to your battery/batteries. (energy stored)
Before we figure those factors, we first should know how the solar panels work in RV system, so that we can learn the relation between solar panels and other units.
How Do RV Solar Panels Work?
We assume that you have a solar panel on the roof of your RV. If your RV is on the road or parked during the day, sunlight hits your solar panel, and cells on the panel absorb energy from the sun.
Inside the solar panel 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 is DC (direct current) electricity that charges your RV’s battery or batteries, essentially “storing” energy to be used to power devices and appliances in your RV.
For a 12V RV electrical system, this DC power from the solar panels and batteries is typically 12 volts. This DC power runs lights, appliances, and other 12V DC electronics in the RV.
As for those typical 110V/120V house appliances, you can also take that 12V DC, pass it through an inverter, and convert it to 120V AC (alternating current) electricity to power 120V devices such as a coffee pot.
If you want to run a 120V appliance when you’re boondocking in somewhere without shore power, you can obtain the sun’s energy through solar panels — charge controller —batteries — inverter, and then the 120V electricity in your hands.
After knowing the working principle of the whole RV electrical system, you can consider about how many panels you need for your RV.
As we learn from the relation between solar panels and batteries, 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 fill those batteries for your use.
Calculating How Much Energy You Use
Calculating your average daily energy consumption is the first step to determining what size RV solar system you need. To do this, you'll need to make a list of the appliances you want to use, how much power they require and how many hours per day you'll use them.
For example, let's say you have a 500-watt microwave that you want to use for 15 minutes each day. By multiplying these figures, you can determine that you'd need to generate 125 watts of electricity just to use your microwave for that amount of time, 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
To figure out how much electricity your system will generate per day, you need to multiply your system size by how many hours of direct sunlight your panels would receive daily.
For our example, let's assume we have an RV solar system that's composed of four individual solar panels generating 100 watts each, giving us a total system size of 400 watts. We'll also assume that we're in a reasonably sunny area that receives at least 4 hours of sunlight per day.
With some quick math, we can see that this system will generate 1600 watt-hours (Wh) of electricity per day. You can use this output as a benchmark to compare against your energy needs (calculated above) and storage capacity.
You’ll also need to know how many batteries you’ll need to store that amount of power! One 100 ah 12volt lithium 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.
Choose the Right Panels Amount for Your RV
After knowing how big solar power system you need, you could now select the suitable-size panels for your RV roof. The size among 100W, 200W, 300W panels are different, to avoid the unable mounting situation, it’s necessary to evaluate what size and how many of the panels can be put on your van’s roof.
Here is one table for you to have an overview
(Data varies in different model options)
Panels and RV Electrical System
When you mounting multiple solar panels on RV ‘s roof, one more thing you need to think is if the panels should get wired in series or parallel. Different connecting method brings you unequal array voltage and amperage. Actually, it depends on what your current battery bank is or what type you gonna build, 12v or 24v, or even 48v solar power system on luxury trailer.
If you have no idea about the differences between those three systems, here is one article about How to choose RV electrical system.
Key Components for RV Solar Power System
Before the installation, it’s better to review the components, to see if you’ve got all of them for mounting.
Battery Bank
The 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, it’s where the panel’s current goes.
But not all battery banks are created equal, and not all are suited to the unpredictable charge cycles of solar power systems. Usually, lead-acid batteries and lithium batteries be considered as the common solar batteries, due to their rechargeable features, but still there are many differences between them.
Read The difference between Lead Acid battery and Lithium battery to learn more about them.
There are two general kinds of solar panels for RVs: monocrystalline and polycrystalline
-Monocrystalline panels are the most efficient (and most expensive) of the three, so they will generate the most energy in the least amount of time.
-Polycrystalline panels are slightly less efficient, but they're a durable and reliable option.
To find out more detailed difference, you could read Basic knowledge of solar cell components.
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 charging rate to your battery, so it will not be over-charged, and the lifespan could be secured.
Normally, you’ll see PWM and MPPT charge controller on the market, the MPPT one is more efficient, and PWM cost less. Here one page help you to Choose an Appropriate one.
The electricity from your batteries is DC electricity. With this, you can power all DC appliances in your RV. If you want to use 120V AC electricity to power a coffee maker, laptop, or anything that requires AC, you’ll need an inverter that transforms 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.
Steps for Setup all Components
Here are the steps to connecting your solar panels to your batteries:
1. Mount your solar panels on the roof of your RV.
2. Mount your charge controller inside the RV as close to your batteries as possible.
3. 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.
4. Connect the panels array to the charge controller. You should install a fuse or circuit breaker on the wires.
5. If you have an inverter, put it inside and be as close to the batteries as possible. Connect it with the batteries with appropriate wire, you should check the battery bank total current to confirm the suitable wire gauge. Also, there should be one fuse in between the battery bank and the inverter.