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Knowing how much solar power your RV needs is an important first step when transitioning to solar.
A small solar setup will not be able to run all the appliances you need. On the other hand, a large solar power system will be very costly and wasteful in terms of power.
To find the number of solar panels for your RV, you need to calculate your total power needs.
So, how much solar power do I need for my RV when boondocking?
Well, it depends on the amount of power you use daily. A small teardrop type of camper may get through with a single 100w panel. On the other hand, a fifth wheel will need multiple panels and batteries to fulfill its daily power demand.
In this post, I’ll help you determine your total power needs, the number of solar panels you need to produce that power, and what it will cost.
Lastly, I’ll talk about the battery setup to store the power and give you tips on saving electricity without sacrificing comfort.
But, before that, let’s look at how solar power works.
Table of Contents
- How do Solar Panels Work on an RV?
- The Balance between Solar Power Generation and Load
- How much Solar Power do I Need for My RV?
- Watt-Hours to Amp-Hours Conversion
- How many Solar Panels do I need for my RV?
- How much Solar Battery Capacity do I Need?
- Energy Conservation Tips
How do Solar Panels Work on an RV?
The primary function of solar panels is to produce electricity and charge RV house batteries. The appliance uses the power from the batteries to run.
As the sun’s rays hit the solar panels, the photovoltaic (PV) cells in the panel convert the energy from the light to electricity.
The power produced by the solar panel is Direct Current or DC.
This power is fed to a charge controller, which then charges the house battery.
At this point, you can run all your 12v DC appliances like lights, fans, water pump, etc., directly from the battery.
However, to power your household appliances like TV, hairdryer, microwave, etc., you need an inverter to convert DC power to 120v AC (Alternating Current).
To Know: Motorized appliances like fans, water pumps can work when connected to solar panels directly. However, the voltage fluctuations may damage other appliances.
The Balance between Solar Power Generation and Load
Before calculating how much solar power you need, we to understand a vital equation:
The Energy Produced = The Energy Used
That is, the amount of power we produce and store on a given day is the amount of power we get to use.
In other words, we want our solar panels to produce sufficient power to replenish the battery with the power used.
This is important because once the sun is down, your solar panels will not produce any power. You’ll be using the power that you have stored in your batteries.
But, the problem arises when you have an imbalance in this equation.
Let me explain.
Let’s say you’re camping in an area that gets around 8 hours of solid sunlight.
The solar panel array on your roof is recharging your battery bank in about 4 hours. Once your battery is fully charged, the power produced by your panels is a waste because you don’t have a place to store them.
Designing an RV solar power system that produces more power than you can use and store is a waste of energy and money.
Now, let’s say the number of solar panels mounted on your RV is not sufficient to put back the power used in a day.
This is also a loss.
What we want to achieve is a balance between both sides of the equation.
We want our solar panels to produce enough power to recharge the house batteries of what is used. This will help us design the perfect size solar system while also saving a lot of money.
And that is what we’ll do in the rest of this post.
How much Solar Power do I Need for My RV?
To accurately determine the total power we need and the number of solar panels to create this power, we need to solve the above equation.
Let’s start by decoding the right side of our equation first.
i.e. How much power do we use daily?
Failing to calculate your daily power usage will lead you to either under-sizing or over-sizing your solar power setup.
Here are two of the best ways to find out your total wattage needs when boondocking.
Method#1: Make a List of Appliance Wattage
This method will help us estimate the total power needs of our RV by finding the wattage ratings of each appliance and adding them up.
One a paper, make five columns and mark them as below:
Now, starting from the front of your RV, note down the name of all the appliances that you use daily. Next, note down how many of the same appliances you use simultaneously.
In the next column, note down the wattage rating of each appliance. You’ll find the wattage ratings of each device on a sticker on the device or use the user manual to find it.
Then, in the Hours/Day column, mention the total hours you use each appliance per day. Lastly, multiply the watts of each device by the hours of use to find the total watt-hours of each appliance.
Then, add up all the watt-hours of all the appliances, and you have your total power consumption for a day.
Let’s use an example to make it more clear.
Our morning starts with an hour of news on the TV while preparing and eating breakfast. We make our coffee by boiling water on the propane stove.
Then we turn on our laptops and get the work done scheduled for that day. We work online and spend about 4-5 hours on the computer each day.
Our 3-way refrigerator runs on both electricity and propane. I usually run it on electricity during the day when the panels are producing power.
As the sun goes down, our camper is lit using LED lights. We have 10 of these lights around our camper but try not to use more than 3-4 lights at a time.
Our day ends with dinner and a bit of Netflix on the TV.
We have two cellphones that we charge once a day, and our internet router is only off when we sleep.
We run a few more appliances, but those don’t fall in our daily use bucket.
This is just an example list to get the point across.
Therefore, on a typical day, we use about 3729 watt-hours of power.
Every RVer is different, and the total electricity they need will differ.
However, once you find out the total watt-hours you use, you need to add 20% to the number. This will give you a buffer space if you need extra power and accommodate the parasite drain on the battery.
For me, 3729 watt-hours plus 20% is 4500 watt-hours. Now, I can work on the size of my battery bank and how many solar panels I’ll need to recharge the battery of the depleted power.
This method will give you a rough estimate but is not the most accurate way to determine how much power you use.
Note: If an appliance is used for a few minutes, we need to convert our appliance usage time to hours. To convert minutes to hours, simply take the minute and divide it by 60 (1 hour in minutes).
Method#2: The Camping Test
To find out how much energy you use in a day when boondocking is to go on an actual trip. This method is the most accurate and is more fun compared to walking around your camper with a pen and paper.
To begin with, do your research and find a good boondocking site to set camp.
You need to carry your portable RV generator, irrespective of the type and number of house batteries you have pre-installed. You have house batteries installed means you have a battery monitor installed too.
Note: A battery monitor is crucial to get accurate results, and you need to install one if your RV doesn’t come with one pre-installed.
Make sure the house batteries are 100% charged before you reach the campsite.
Once on the campsite, use electricity normally as you use on any other trip. Don’t treat this trip as anything special, and try to conserve the maximum energy you can.
Keep an eye on your battery monitor to know how much you have used and how much power is left.
Keep In Mind: Lead-Acid batteries cannot be discharged past 50%, as it will damage the battery. Whereas, Lithium-Ion batteries can be discharged up to and past 80% without damage.
That means, if your RV comes with a 100 amp-hour Lead-Acid battery, you have just 50 amp-hour of usable energy. You can always use your RV generator to recharge your house battery if it falls low in the middle of your trip.
However, make sure to use the generator to charge the battery and not other things, as this will put the result off.
At the end of your trip, you’ll have an accurate reading of how much power you have used during your trip.
To get the best result, go on a long or a few shorter trips. The more data you have about your power usage, the more accurately you’ll be able to size your solar panels and battery bank.
Read More: How much solar power do you need to run an RV air conditioner?
Watt-Hours to Amp-Hours Conversion
Now you have determined how many watt-hours of power you use daily. This is also the minimum amount of wattage your solar panels need to produce to create a balance between energy created and consumed.
However, your house batteries are rated at amp hours. You have to convert the watts produced by the solar to amp hours to know how much battery power you need to store this power.
There is no straightforward way to find out the Watt Hours and Amp Hours. But, it is not very difficult if you know a simple formula.
It’s known as Watts Law.
Watts law states that:
Power (watts) = Voltage (volts) x Current (amps).
Therefore, we can say:
Amp Hours = Watt Hours / Battery Voltage
Battery voltages are usually printed on the battery, and we’ll assume our battery to be 12 volts.
Now, plug in the total watt-hours you found in your power audit and divide it by the battery voltage.
This is the total amp hours of battery storage you need.
In my example power audit above, I found my total energy needs per day is about 4500-watt hours.
Let’s plug this into the above equation.
Amp hours = 4500 watt hours / 12 volt battery
Amp-hours = 375
Therefore, to meet my daily power needs, I’ll need my solar panels to produce about 4500 watts of electricity and 375 amp-hours of battery capacity to store this power.
How many Solar Panels do I need for my RV?
Now we know how much power we need to camp per day and learned how to calculate our power needs accurately.
In this section, we’ll decode the left side of the power balancing equation.
i.e. How much power do we need to produce?
In other words, how many solar panels your RV needs to create the power you use daily.
In addition to the total power usage per day, you need to factor in a few more things to find out the number of panels you need for boondocking.
How much Energy does A Solar Panel Produce per Day?
To accurately calculate your solar array size, you need to know how much power each panel produces.
However, this is not the most straightforward thing to find.
Solar panel manufacturers rate their panels at max efficiency. But this efficiency is only attained at an optimal condition. Meaning, there will be a difference between the mentioned and the actual output of the panels.
For example, a 200-watt panel will not produce 200 watts of power. There will be a drop in the output rating.
This is because the power output or efficiency of a solar panel depends on a wide variety of factors like:
- Type of panel
- Weather conditions
- Duration of sunlight
- Time of the day
- Panel tilt angle
- Your camp location
- Dirt in the air and on the panel
Therefore, use an efficiency level of 75-80% when designing your solar array. This way you’ll get higher outputs as the optimal conditions are met.
How much Space is Available on the Roof?
Solar power is unlimited, and you can increase how much power you produce if you add more panels to your solar array.
However, you can only add so many panels on your RV roof as the space up there is limited.
Therefore, calculate the available roof space and the size of each panel you’re planning to buy.
But, what if your wattage needs are more than the usable space on the roof?
In such a situation, you’ll need to go for higher wattage single panels. Like, instead of 100-watt panels, you now have to get single 200 or 300-watt panels.
You can also use portable solar panels to add to your power output.
How much do Solar Panels Cost?
The price of a solar panel is the last piece of the puzzle when finalizing how many solar panels you’ll be buying to power your RV.
Price is a very subjective matter, and everyone has different financial flexibilities.
But keep in mind that the price and warranty period of a product is the direct indicator of its quality.
Solar technology has evolved a lot over the last decade that you’ll find good quality panels ranging in price from $0.5-1 per watt.
A good rule of thumb is to get the most expensive panels you can afford. Quality panels will easily last and perform over two-plus decades.
Putting it All Together
Let’s say we have accurately calculated our total power needs, and it equates to 50 amp-hours per day.
The solar panel you’re planning to buy is a 200-watt monocrystalline single panel that is rated at 11.76A. It also comes within your budget range and dimensions.
For the sake of this example, let’s also consider the conditions are perfect for solar, and you’re getting 6 hours of solid sunshine.
With this 200 watt panel, you should be able to recharge the 50 amp hour used in about 4.25 hours (50/11.76A).
Most importantly, even the tiniest of the campers will comfortably fit a 200w panel on the roof.
How much Solar Battery Capacity do I Need?
Your battery bank is one of the most important components of your RV solar system.
Your solar panels are only functional when the sun is up. Though, you can connect motor-based appliances like fans, water pumps directly to your solar panels.
But your household electronics will be damaged if connected to the solar panels directly.
Plus, as the sun goes down, your solar panels will no longer produce any power. You need a way to store the energy produced by the solar panels during the day.
And that’s where deep cycle batteries come into play.
However, you just can’t fill up every inch of your RV storage compartments with as many batteries as you can find.
This is because batteries are the most expensive component of your RV solar setup. Most importantly, they are extremely heavy, which may move the center of gravity of your rig or put you over the towing weight.
However, when sizing your RV battery bank, make sure to add at least an additional day’s worth of backup. This will keep you in the safe zone and prevent the need to run your generator if the weather is not ideal.
Let’s say your daily wattage use is about 1500 watt-hours. You need a minimum of 1500 watt-hours of battery storage or better if you can size it up to 3000-watt hours.
To find out how many deep cycle batteries this translates to, we need to convert the watt-hours to amp hours.
Watt-Hours = Amps-Hours * Volts
Amp Hours = Watt-Hours / Volts
Amp-Hours = 1500/12 (12v battery)
You need a total of 125 amp-hours of battery capacity.
The most common capacity of deep cycle batteries is 100 ah (amp-hour). That means you’ll need two 100 ah batteries to keep you powered.
However, a battery with a 100 ah capacity doesn’t mean you can use all the 100 amp-hours. Yes, you can use it but at the cost of destroying your battery.
Lead-acid batteries can only be discharged up to 50%. Whereas, lithium-ion batteries up to 80%.
That means, with a 100 ah lead-acid battery, you get 50 ah of usable power and 80 ah on lithium.
So, to get 125 ah of battery storage, you need 3 lead acid or 2 lithium-ion batteries.
Energy Conservation Tips
Solar energy is unlimited and free, but the amount of energy you can store in your battery bank is limited.
That is why you need to find ways to conserve energy wherever possible.
Energy conservation while boondocking is pretty easy, given you keep a few simple things in mind, like:
- Replace all the fluorescent lights with LED lights as fluorescent lights use 2-3 times more power at the same wattage rating. Plus, LED lights are much brighter and last longer.
- Reduce the use of your furnace, instead use portable propane heaters. The circulatory system in your RV furnace uses a lot of power, and using it thoughtfully will save a lot of energy.
- Use your RV vent fans to circulate air to cool down your camper instead of running your air conditioner. Additionally, keep your awnings extended to keep the camper cool.
- Instead of using an electric coffee maker, brew it on your propane stove.
- Unplug all the unused appliances, including your phone and laptop chargers, as these have a small draw when connected.
- Take army showers to reduce the use of the water pump and heater. This will also save a lot on your precious freshwater.
- Turn off all the appliances when you leave your camper for grocery shopping or going hiking.
- Shift the use of your high draw appliances to when your panels are producing power. Keeping the use to a minimum after sunset will save a lot of power.
Following these simple tips will surely reduce your daily power consumption. However, don’t go too far to save power and sacrifice your and your family’s comfort.
Because if you need extra power after sunset, you can always run your trusty portable generator to put in some extra juice.
The number of solar panels you will need to go boondocking will mainly depend on your power needs and usage habits.
However, mounting all the solar panels your RV roof can fit will not help. You’ll also need an appropriate size battery bank to store the power produced by the panels.
Dry camping with a small solar setup is also possible if you keep the power conservation methods in mind. Then you always will have your generator for those cloudy days to top up your batteries.