Solar Power For Campers: Is Direct Solar Charging Possible?

Solar panels are a great way to power your camper, but there are a few things to consider before you get started. Firstly, solar panels don't come cheap. A quality setup can cost upwards of $1500, and that's before you factor in any additional equipment you might need, such as deep-cycle solar batteries, a charge controller, or an inverter.

Another thing to keep in mind is that setting up solar power for your camper is a little more complicated than simply plugging into shore power at a campsite. To determine how much power you'll need, you'll first need to calculate your daily power usage. This will help you figure out how many solar panels you need and what size they should be.

Additionally, if you plan on using solar power, you'll need a battery bank to store energy for times when you're not getting direct sunlight, such as at night or on cloudy days. Lithium-ion batteries are a good option for this, as they're more compact, lightweight, and have a longer lifespan than lead-acid batteries.

It's also worth noting that parking in the shade can reduce the effectiveness of your solar panels, so if you're looking to stay cool during hot summer days, you might need to find an alternative power source or invest in portable solar panels that can be set up in a sunny spot.

Despite the initial investment and setup process, solar power for your camper is definitely worth considering. It will give you the freedom to go boondocking on public land and save you money on camping fees and electricity costs in the long run. Plus, solar power is silent and low-maintenance once it's up and running.

Solar panels are an expensive initial investment

Solar panels are rated for their max efficiency—that is, a 100-watt solar panel will produce 100 watts in perfect conditions. (And unless you're the luckiest camper in the world or have discovered a way to control the weather, we guarantee you won't always have perfect conditions.) The weather, temperature, time of day, and other factors influence the amount of power solar panels actually generate. There are multiple online calculators available that take your geographic location, the time of year, etc. into account and provide the average usable hours of sunlight you can expect.

The general rule of thumb is that a 100-watt solar panel can produce about 30 amp-hours per day, so you can use this guideline to determine about how many panels you need. Another suggestion is to match your battery capacity in amp-hours with your solar output in watts. A 300 amp-hour camper battery, for instance, would need around 300 watts of solar power. Also, keep in mind that solar panels experience a 75-90% drop in efficiency on cloudy days, so it's good to have slightly more than you need when it comes to solar power (about a 20% cushion, if possible, to account for less-than-ideal conditions).

Solar panels are much quieter and more eco-friendly than using a generator. It is also a great option for boondockers looking to go camping off-the-grid. From what you’ll save on camping fees as well as on electricity costs, it will make up for the expensive initial investment. Solar power is also completely silent unlike a generator, and maintaining your RV solar panels is easy once everything is set up.

Solar power is a little complicated to set up

First, you need to know how much energy you use in a day. There are a couple of ways to do this. The first involves math. Estimate how much power you’ll consume while boondocking in your RV by learning what each device or appliance you want to use consumes and multiplying that by the number of hours you’ll use that device or appliance.

Here’s an example: 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.

A decent assumption is that a 100-Watt solar panel will generate on average 350 Watt-hours of power per day. However, this will vary significantly by location and time of year.

You’ll also need to know how many batteries you’ll need to store that amount of power! One 100 ah 12-volt 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.

It’s also challenging to estimate the amount of power you’ll use on a given day because days are different. You may be outside all day today enjoying nature, and fall into bed and watch 15 minutes of television tonight. Tomorrow could be a rainy day, and you’ll stay inside your RV, do a lot of work on your laptop, and watch a couple of hours of television in the evening. So estimating high is usually a good idea!

Rather than estimating your daily power consumption using math, some people prefer to simply go out camping without electrical hookups and monitor their battery usage over a typical day. Installing a battery meter like the Victron BMV712 before installing solar can give you an accurate reading of how much power your RV needs.

Solar panels are rated for their max efficiency—that is, a 100-watt solar panel will produce 100 watts in perfect conditions. (And unless you're the luckiest camper in the world or have discovered a way to control the weather, we guarantee you won't always have perfect conditions.)

The weather, temperature, time of day, and other factors influence the amount of power solar panels actually generate. There are multiple online calculators available that take your geographic location, the time of year, etc. into account and provide the average usable hours of sunlight you can expect.

The general rule of thumb is that a 100-watt solar panel can produce about 30 amp-hours per day, so you can use this guideline to determine about how many panels you need.

Another suggestion is to match your battery capacity in amp-hours with your solar output in watts. A 300 amp-hour camper battery, for instance, would need around 300 watts of solar power. Also, keep in mind that solar panels experience a 75-90% drop in efficiency on cloudy days, so it's good to have slightly more than you need when it comes to solar power (about a 20% cushion, if possible, to account for less-than-ideal conditions).

In our example from the last section, we know that we use 50 amp-hours per day when camping in our RV. We want to keep our battery at optimal charge, so we're going to need a solar setup that can generate this same amount of power per day. If we look at Go Power's 100-Watt Retreat Solar Panel as an example, we can see that its power output is 5.43 amps per hour.

If we assume 6 usable hours of sunlight per day, that's 32.58 amp-hours per day, which is pretty close to our ballpark figure of 30 amp-hours per day. From here, we can determine that two of these 100-watt panels would give us about 65.16 amp-hours a day, which covers our requirement of 50 amp-hours. Our two 100-watt solar panels equal 200 watts together, which also checks out with our guideline of matching our battery amp-hours with our solar panel wattage. We even have our 20% "cushion," though if we want to add a smaller panel for faster charging or to help pick up the slack on cloudy days, we can do that too.

Solar panels atop RVs are all the rage. Everybody’s installing them. But what are RV solar panels? How do they work, what can they do for you, and are they worth the investment? Let’s find out!

A solar panel is a panel filled with solar cells that capture the sun’s energy and turn that energy into usable electricity that powers homes, businesses, coffee pots, and, yes – your RV!

Let’s imagine you have a couple of solar panels on the roof of your RV. If your RV is on the road or parked during the day, sunlight hits your solar panels, and cells on the panels absorb energy from the sun.

Within your solar panels’ 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 becomes DC (direct current) electricity that charges your RV’s house battery or batteries, essentially “storing” energy to be used to power devices and appliances in your RV or charge devices for your later use.

This DC power from the solar panels and batteries is typically 12 volts. This DC power runs lights, appliances, and electronics in the RV.

However, you can also take that 12-Volt DC, pass it through an inverter, and convert it to 120-Volt AC (alternating current) electricity (like the outlets found in a sticks-and-bricks house) to power 120-Volt devices such as a coffee pot.

There are 120-Volt outlets scattered throughout your RV, but those don’t have power unless you’re using a generator or your RV is plugged into shore power.

If you want to run a 120-Volt appliance when you’re boondocking in the desert, you can harness the sun’s energy through solar panels —> charge controller —> batteries —> inverter, and voila! = 120-Volt electricity at your command!

Theoretically, you can power anything with the sun’s energy provided you have enough solar panels, batteries, and conversion ability!

The anatomy of a campervan solar system involves three components: a solar charge controller, photovoltaic panels (PV), and a leisure battery.

Photovoltaic panels (PV), also known as solar panels, convert energy from the sun (photons) into electricity which you can use to power your campervan. When the sun shines onto a panel, the energy is absorbed by the PV cells. The photons knock electrons free from atoms, generating a flow of electricity.

The solar cells form an electrical circuit in the panel, thus allowing the flow of electrons through the circuit, creating electricity.

In the Roaming Home 2023 study, we found that most people install a 300W campervan solar setup, followed closely by a 400W solar system. Though the results were quite distributed.

When sizing solar panels for off-grid living, it's essential to balance your energy consumption with the solar panel output and battery storage. Start by calculating your daily energy usage using an energy consumption calculator. Then, ensure your solar panels can generate enough energy to cover that demand, even on less sunny days.

Steps to Size Solar Panels:

Estimate Daily Load: Add up the watt-hours (Wh) of all appliances and devices you'll use daily.

Factor in Solar Efficiency: Account for system losses (inverters, wiring), and local solar irradiance data (hours of sunlight per day).

Choose Appropriate Battery Storage: Ensure you have enough storage to handle several cloudy days.

For full-time off-grid living, a 300-400W solar setup is common, but higher capacities may be needed depending on your consumption and location.

To help you figure out what size solar panels you will require for your van conversion, we have built a solar panel calculator. First, you will need to figure out your expected daily electrical load, which you can calculate using our energy consumption calculator.

Use the solar panel calculator.

Solar panels perform differently depending on a variety of factors, including geographical location, time of year, weather, and tilt angle. Understanding how these conditions impact solar energy production can help you optimize your campervan's solar system and set realistic expectations for how much power you'll generate.

Key Factors Affecting Solar Output:

Geographical Location: Solar energy is more abundant in some parts of the world than others due to varying solar irradiance (the amount of sunlight reaching the earth). For example, places closer to the equator receive more consistent sunlight throughout the year compared to higher latitudes.

Example: In southern Spain, solar panels can produce up to 40% more energy annually than in northern Germany, due to the difference in sunlight hours and intensity.

Solar panel output fluctuates significantly with the seasons. In the summer, longer daylight hours and a higher sun angle increase energy production. In the winter, shorter days and lower sun angles result in reduced energy output.

Example: A 300W solar panel system in London might generate around 1.2 kWh/day in summer but only 0.3 kWh/day in winter.

Cloud cover: On cloudy days, solar panel output can drop by 50-90% depending on cloud density.

Rain: While rainy conditions reduce sunlight, rain can actually improve solar panel efficiency by cleaning off dirt and debris that could otherwise block sunlight.

Temperature: Contrary to popular belief, solar panels work more efficiently in cooler temperatures. While panels are most effective under direct sunlight, cooler temperatures can increase their efficiency due to lower thermal losses. Heat increases the electrical resistance in solar cells, reducing their efficiency. Panels operating in cooler climates can sometimes outperform those in hot, sunny regions despite receiving less sunlight. For every 1°C drop below 25°C, solar panel efficiency can improve by 0.3-0.5%, depending on the panel type.

Solar Panel Tilt Angle and Orientation:

Solar panels perform best when they are angled directly towards the sun. The optimal tilt angle changes depending on your latitude and the season. Panels mounted flat on your van roof will produce less energy than those with an adjustable tilt, especially in winter.

Tip: Use a tilting mount to adjust the panel angle based on your location. If you're in the northern hemisphere, tilt panels at an angle equal to your latitude for optimal year-round performance.

Real-World Energy Production Examples:

300W Solar Panel System in California (Good Sunlight): This system can produce approximately 1.2-1.5 kWh/day on average in summer and 0.6-0.8 kWh/day in winter.

300W Solar Panel System in Scotland (Less Sunlight): In summer, it might produce 0.8-1.0 kWh/day, while in winter, output could drop to 0.2-0.4 kWh/day due to the lower sun angle and shorter days.

Tools to Calculate Solar Potential:

To estimate the energy your solar panels will generate given your specific conditions, use a tool like the Global Solar Atlas. These tools allow you to input your location and system specifications to get a detailed estimate of solar energy production under different conditions.

The ideal angle for a solar panel installation is roughly equal to the latitude you are currently residing (not accounting for seasons). If your panels are perpendicular to the sun, and pointing directly at it, you will have a big increase in efficiency.

The anatomy of a campervan solar system also includes a solar charge controller, which is a device that keeps our leisure batteries from overcharging by regulating the voltage and current coming from the campervan solar panels. It converts the powerful electricity from our solar panels into electricity our leisure batteries can use.

A solar charge controller ensures that the voltage and amperage match the expecting charge stage of the battery. It is paramount that it does its job correctly. For example, if we had a campervan solar panel installation with four panels wired in series (74.4V) wired directly to our leisure batteries, the sulphuric acid would begin to boil and we could be in for a very, very dangerous time indeed.

There are two types of solar charge controllers: MPPTs (Maximum Power Point Tracking) and PWMs (Pulse Width Modulation).

A PWM is a relatively simple device that is essentially a smart switch. It pulsates on and off, recognizing when it needs to send power to the batteries (per the charge profile). It is about half the price of an MPPT, but about 30% less efficient per day (big difference!).

PWMs draw current from the campervan solar system just above the voltage of your leisure batteries.

A MPPT is a solar charge controller that digitally tracks the charge profile of the leisure batteries in order to be as precise as possible with its energy delivery. They are a lot more efficient than PWMs.

MPPTs are a little more expensive, but accelerate solar charging of the battery up to 30% per day. MPPTs are slowly but surely taking over from PWMs entirely.

MPPTs draw current from the campervan solar panels at the max voltage possible.

Sizing your MPPT correctly turns out to require some fairly complicated math. To simplify things, we have built an MPPT sizing calculator, which figures out exactly what MPPT you will need.

Use the MPPT calculator.

To simplify the math and give you a simplified overview of how to size an MPPT; let's say we have four 100W solar panels wired in series flowing to our 12V batteries.

We must figure out how many amps at 12V our solar panel set will actually produce. We can see that our solar charge controller must be able to handle 400W ÷ 12V = 33.7A. So we should buy a solar charge controller that is slightly bigger, for example, a 40A solar charge controller.

In this step-by-step guide, I will be showing you how to install solar panels on the roof of your campervan. First, we will look at how to install flexible (thin film) solar panels, then we will look at how to install rigid mono/polycrystalline solar panels. I have flexible solar panels on my campervan because they are more discreet than solid.

Note: Before we hop in, go grab yourself a wiring diagram, which you can get for free by signing up to The Van Conversion Newsletter (the wiring for the campervan solar system is included in the diagram – wiring diagram gets sent out to you straight away).

How to install flexible solar panels on a campervan:

Step 1: Clean the roof.

Step 2: Remove rust from the top of the campervan.

Step 3: Stick strips of 3M VHB (Very High Bondage) tape on the van.

Place strips of the double-sided 3M VHB tape on the roof of your van. This stuff alone will stick the campervan solar panels down for life.

Step 4: Stick the flexible solar panels onto the roof of the campervan.

Flexible solar panels on top of the 3M VHB strips and gently press them down.

Solar panel temperature: Cooler solar panels are more efficient. Flexible solar panels can get quite hot if there is no air gap underneath them. Luckily on the Ford Transit, there are ridges that run down the length of the van, providing an air gap of about an inch, through which air can flow. If your van does not have ridges, you can still install flexible panels, though they might not be as efficient. Alternatively, you could raise the panels up using metal risers.

Air tightness: Some people use high bondage glue (like sikaflex) instead of VHB tape. This is fine too. However, if you are using glue, make sure you pour it in strips, just like the VHB tape. DO NOT make an airtight seal with the glue - water can get trapped in there, expand, and do damage to the panels. It will also reduce the efficiency of the panels due to higher heat.

Some people choose to secure the panels to their van even more by using well nuts in each of the four corners of each solar panel. A well nut is like a rivnut / plusnut; it is used to fasten something to a surface and to seal the bolt hole. As the bolt is screwed in, the well nut expands on the inside, thus locking it in place.

I can tell you that after years of living in my van full-time, using only VHB tape, I have never had a single problem with my solar panels coming loose. In my opinion, nuts are not really needed.

How to secure solar panels with well nuts:

Drill a hole through the van to match the corner of the solar panel. The hole size should match the size of the well nut (M8 - M10 preferable for a solar panel).

Place the well nut through the panel and into the hole.

Screw an appropriate bolt into the well nut, and the well nut will gradually expand and seal the hole.

For extra waterproofing

You'll need a battery bank to store power

Solar panels are rated for their max efficiency—that is, a 100-watt solar panel will produce 100 watts in perfect conditions. (And unless you're the luckiest camper in the world or have discovered a way to control the weather, we guarantee you won't always have perfect conditions.)

The weather, temperature, time of day, and other factors influence the amount of power solar panels actually generate. There are multiple online calculators available that take your geographic location, the time of year, etc., into account and provide the average usable hours of sunlight you can expect.

Lithium-ion batteries, though more expensive, are a better option for solar energy storage than lead-acid batteries. They're lighter, more compact, and have a longer lifespan.

You'll also need to know how much power you use in a day. There are a couple of ways to do so.

Figuring out how much energy you use in a day means looking at your battery and determining how charged (or not) it is. You never want to drain your lead-acid battery lower than 50%, as this can damage the battery and shorten its lifespan.

Monitoring your battery sounds pretty simple until you realize stock RV battery voltmeters don't provide the most helpful information. If you have one of these, you'll see numbers like "12.6," or "12.3," which tell you pretty much nothing if you don't know what you're looking at. Basically, a fully charged RV battery will put out about 12.6+ volts. An RV battery at 50% battery will put out between 12.06-12.10 volts, on average. If your voltmeter has a number below this, charge your battery immediately.

If you're going to be boondocking a lot, however, it's definitely worth investing in a decent battery monitor or gauge if your RV didn't come with one. There are a lot out there, ranging from very simple models to state-of-the-art battery management systems. At the least, you want to look for a system that will provide a simple charge percentage indication. It's a lot more straightforward to simply have your monitor tell you your batteries are at 80% than to try to figure out what 12.4 on the voltmeter means.

Once you know how much power is actually left in your RV (either by checking the voltmeter or by reading the battery monitoring system), you can use this information to determine how much energy you use per day using one of the two methods below.

The best way to figure out how much energy you output is to actually go camping. (This is also more fun than a spreadsheet.) If you can make multiple camping trips, even better. Follow these simple steps to determine how much power, on average, you consume in a day:

Step 1: Settle out in the boondocks for a couple of days and use your RV as you normally would—don't try to conserve power any more than you usually would, and don't use your generator. Just camp normally.

Step 2: Use your voltmeter or a battery monitor to keep track of your battery level. Note that lead-acid batteries should never be discharged below 50%. Going below this mark will shorten the battery's lifespan.

Step 3: Do the math to determine how much power you typically consume in a day. Let's say after two days, your 200 amp-hour lead-acid batteries are at 50%. This means you used 100 amp-hours in two days, or 50 amp-hours a day.

If you can't even make it through a day without draining your battery, consider adding to your RV's battery bank. All the solar panels in the world won't help if you don't have enough battery capacity to store the power you require. Ideally, you should be able to go at least 2-3 days before your battery is depleted.

When boondocking, it helps to get in the habit of conserving energy. Try these tips below:

• Unplug electronics when not in use (phones, tablets, etc.), or charge them while driving if possible
• Adjust your daily routine - read during daylight hours, vacate the camper during the day instead of using fans, etc.
• Replace older TVs with efficient, LED flat screens
• Shorten your shower time
• Park under shady trees or use your awning to keep cool; conversely, layer up to keep warm

Parking in the shade can be tricky

If you want to park in the shade, portable solar power units might be a better option. They are often easier to set up and can be moved to a sunny spot. Quality portable solar electric systems are made by Renogy, Acopower, and Eco-worthy. Goal Zero also makes portable power stations, which have a built-in inverter and outlets for your electronics.

If you already have rooftop panels, check out this easy mod from Do It Yourself RV on how to make them portable.

Solar power is worth the investment

Solar power is a big decision, and there are a lot of factors to consider before buying expensive panels for the roof. The first thing to consider is how much power you use on a daily basis. That lets you figure out how much power your solar panels need to generate. This is important because solar panels are rated for their max efficiency—that is, a 100-watt solar panel will produce 100 watts in perfect conditions. The weather, temperature, time of day, and other factors influence the amount of power solar panels actually generate.

The next thing to consider is how you will store the energy. You will need a battery bank to provide power for nighttime, cloudy days, and when you want to park out of the sun. Lithium-ion batteries, though more expensive, are a better option for solar energy storage than lead-acid batteries. They’re lighter, more compact, and have a longer lifespan.

Finally, you will need to consider the placement of your solar panels. On a hot summer day, you may want to park the RV in a nicely shaded campsite out of the blistering hot sun. However, solar panels won’t generate nearly as much power if they are not getting direct sunlight.

Overall, solar power is absolutely worth the investment. It gives you the ability to go boondocking on public land rather than having to stay in a crowded RV park with hookups.

Frequently asked questions