Upgrading your RV to solar power is a big deal, and comes with a lot of questions which can make the process overwhelming. How many panels will provide the power I need? How much power do I need? What size panels should I get? Is it even worth the upgrade?
This article will break down how to best calculate how many solar panels are needed for your RV, and whether or not this is a “best choice” investment decision for you.
The bottom line? The number of solar panels needed for your RV will depend on a number of factors, including how much power you need, the size of your RV, and your ability to store the energy generated. Let’s get into it.
Solar Power – How to Figure Out What You Need
If you’re in that place where you’ve decided you want to convert to solar power, but you just don’t know what to buy, you need to first figure out how much power you actually need.
Solar power is a balance of two things: power used and power stored.
Power used is the amp hours (amperage a battery provides per hour) used each day.
Power stored is the energy your solar panels provide to your battery, which powers the majority, if not everything, in your RV.
Basically, you need to figure out how to best balance these two things in order for solar power to work for you.
Solar panels can be incredibly pricey, so it’s best to figure out this balance way in advance before you end up purchasing things you don’t need, or underestimating what you actually need in terms of power.
If you don’t have a place to store the energy your solar panels generate, then covering your RV with solar panels is a total waste of money.
On the other hand, you don’t want to be stuck running out of power because you don’t have enough panels generating the energy you need.
To figure out how much power you’ll need to keep your battery or battery bank lasting, you need to determine how much energy you use in a day when taking your RV out on the road or camping.
How to Calculate Power Used
There are two main ways to do this.
First, you can estimate your daily power consumption based on which appliances are being used in your rig, adding up the total there, and using that number to determine the number of solar panels you’ll need.
Here’s the problem with this method: you’re totally guessing how much energy you need based on what you think your appliance wattage is, and how many hours you use them. These things can really vary depending on the day, making this method pretty variable. This ends up just being a headache, and the consequences of you being wrong can be expensive.
The second method, simply taking your RV out on the road, is the preferred method to calculate how much energy you use. Try these steps to figure out how much power you’ll need, on average, in a day:
- Take your RV out camping – somewhere where you don’t hook up to a power bank – and use your rig like you normally would. Don’t try to conserve power! This defeats the point of calculating your average power usage.
TIP: If you can’t make it a day without charging your battery/running through your power, you may want to consider adding to your battery bank. Remember, it doesn’t matter if you have 100 solar panels if you don’t have anywhere to store your energy!
- Use a battery monitor and keep track of your battery level in a log. Don’t stare at it all day long; just check up every few hours to note your level.
Note: lead-acid batteries should not ever go below the 50% mark. There’s a possibility of your battery dying, and this can shorten the lifespan of the battery.
- Here comes the tricky part: you now need to calculate how much power you consume daily based on your battery level.
Think about it this way: let’s pretend that after two days your 200 amp/hour battery is at 50%, so 100 amp/hours have been used in two days. This means you’re using 50 amp/hours a day.
How to Calculate Power Stored
So now that we’ve figured out that you use 50/amp hours per day in energy, we can now turn to the main question: how many solar panels do I need to provide this energy, and then some?
To figure this out, we actually need to look at how much energy and power a single solar panel produces. There isn’t one straight answer here – it depends.
Here’s a handy chart detailing panel and battery needs depending on your energy usage. It’s better to calculate solar panel needs not by how many you need, but how much energy you need to produce:
|Amp Hrs Needed Per Day||# of 12v Batteries Used||Solar Kit Size (Watts)|
Your amp hours here are calculated based on 5-6 hours of sunlight each day.
So, because we’ve figured out you’re using (on average) 50 aH (amp hours) per day, you’re probably going to want to have two batteries, and a 170 or 190 watt solar kit.
Why don’t we talk about the number of panels? Because it really depends on the manufacturer of your solar kit. Depending on how much energy each panel can convert, you may need one solar panel or you may need three!
Solar Panel Efficiency
If you want to bypass that chart and really get deep into how efficient a solar panel can be, this section is for you.
Solar panels are rated for max efficiency. Meaning the wattage is labeled based on how many watts of energy a solar panel should be able to produce on a perfect weather-condition day.
Naturally, you won’t always have a perfect, sunny day (unless you know something we don’t know!) so the actual amount of power your solar panels generate may vary. This will also change depending on the weather, time of day, geographic condition, etc.
Even though these numbers can be variable, there are some basic estimations you can do to determine how many solar panels you might need.
Calculating the Number of Solar Panels Needed from Energy Used
Generally, a 100-watt solar panel will generate around 30aH per day. There you go – the basic calculation you were looking for this whole time. So, if you use 50aH a day, you’ll want two, 100-watt solar panels to fit atop your RV.
Keep in mind that you’ll want to account for solar panels dropping in efficiency due to weather. Generally, expect solar panels to be at 75-90% efficiency. Therefore, it’s always better to have slightly more solar panels just to produce the energy you need.
Calculating the Number of Solar Panels Needed from Energy Produced
Say you have a solar panel that is 100W, and it produces 5.5 aH (amps per hour).
On average, there are 6 hours of sunlight in a day that are considered “usable” for solar panels. So, we can assume that our solar panel in question is going to produce 33 aH a day. That’s on par with our average calculation of 30aH a day.
Like we calculated earlier, we use around 50aH a day, so one of these 100W solar panels is not going to be enough. Two, on the other hand, could be perfect.
If both are performing at optimal levels, then we’ll be able to generate 66 aH – more than enough to get us through the day, even accounting for suboptimal weather.
So there you have it – multiple ways to calculate how many solar panels you might need!
If you’re considering how many solar panels you might need for your RV, you also want to consider the size of the solar panel, which will affect how much energy it can produce.
For tips and tricks on how to install solar panels, head to this handy guide.
Hopefully, this article will have helped you determine how many solar panels you need for your RV. The goal is to get as much bang for your buck as possible, without the headache of overspending. Unfortunately, this may take some math on your end, but if your calculations are correct, you’ll end up happy and energy efficient!
As always, while you can DIY this process and install your own solar panels, if in doubt, you should consult a professional.