So you’re at the beginning stages of your solar system build and you might be asking yourself, “How much solar do I need to put on my campervan? 100-watts? 300-watts? Or more?”
It’s a question that we’ve all asked ourselves at one point or another and the answer typically is: IT DEPENDS!
So in this post, we’re going to talk about how to accurately calculate just how much solar power (total watts) you need to sustainably power all the electric devices in your camper van.
If you’re ready, let’s get to it!
By the end of this section, you should be able to answer the following questions:
Basic Misconception Of Solar Power
But before we get to calculating your van solar power size requirements, it’s critical to go over one common misconception regarding solar power.
You might be thinking that the size of your solar system is derived from the total power consumption of all the electrical devices you have in your camper van.
The answer? Yes & No
Yes: The more power demanding your devices, the larger the solar wattage system you’ll need.
No: Solar panel size is not DIRECTLY derived from the power draw of your electrical devices.
What Does This Mean?
This means, in order to know how much solar power you need for your campervan, you’ll first need to calculate an appropriate battery bank size that can adequately power all your electrical devices.
Step 1: Calculate The Ideal Size Of Your Battery Bank
If you haven’t done so already, we recommend opening up a new browser tab and reading our other post below on how to correctly calculate the required battery size for your campervan.
How Many Batteries Do You Need?
Don’t run out of juice! Want to build an electrical system that will keep up with your power demands? It all starts with correctly sizing your campervan battery bank. Check out this post to learn more.
Once you’ve calculated your battery size, continue to step two, below.
Step 2: Calculate Solar Array Size From Battery Bank Size
Assuming you properly calculated your battery bank size from Step 1, you can now size the total wattage of your solar array based on the type of battery chemistry you have:
Have Lithium Batteries?
Aim for at least a 1:1 ratio of solar watts to total battery amp-hours (Ah).
So you’ll be looking to install at least 100 watts worth of solar panels for every 100Ah of lithium batteries you will have.
If you have 400Ah of lithium batteries, you should be installing at least 400-watts of solar panels on your campervan.
Have Lead-Acid (AGM) Batteries?
Aim for at least a 1:2 ratio of solar watts to total battery amp-hours (Ah).
So take your total amp-hours (Ah) of your lead-acid battery bank and divide that figure by two. The resulting number is the minimum number of watts for your solar array system.
Lead-Acid (AGM) Example
If you have 400Ah of lead-acid AGM batteries, you should be installing at least 200-watts worth of solar panels on your campervan.
Sizing your van’s solar array using this calculation should ensure that your power intake from your solar panels will meet your daily energy consumption, whether you’re parked in sunny weather or under the occasional shady place.
Want To Add Even More Watts Of Solar? GO FOR IT!
The calculations above are merely a guideline to ensure you have the minimum amount of solar watts to properly power all of your campervan’s electrical devices under most sunny situations.
Of course, if you’re able to fit a slightly larger solar array system on your campervan, we encourage that, too. In our case, we actually have 50-watts of solar MORE than our own minimum guidelines.
We encourage this for two reasons.
1. Solar Power Is Inconsistent
Shade and cloudy days have a detrimental effect on a solar array’s ability to generate electricity. Even if a solar array is only 10% shaded, electricity production from a solar array can drop by over 50%.
For more, Unbound Solar has a short, informative post on the effects of shade on solar panels.
“But what does this mean for me?”
Having a larger solar array system allows you to better weather extended periods of time when parked in shaded areas.
- Camping directly under a thick canopy of trees,
- Driving all day along shaded forest roads
- Traveling during rainy and cloudy days
In our experience in real life situations, daily solar intake greatly varies from day-to-day.
In the above graph, we show our daily solar power intake over a 19-day span. You can see that our daily intake can vary wildly depending on where we travel and park.
Though we tend to produce an average of about 650 watt-hours (Wh) of power per day, in reality, we can produce as much as 1,400 Wh and as little as 150Wh per day.
Each day is different.
Therefore, if your budget allows, we really recommend overestimating your solar panel needs. Even an extra 100 watt panel can make a huge difference in the solar sustainability of your camper van electrical system.
How Do We Measure Our Daily Solar Production?
Wondering how we managed to collect our solar data in the above graph?
We use a Victron MPPT Solar Charge Controller. Unlike most other charge controllers, this particular unit is Bluetooth enabled and pairs with the very useful VictronConnect smartphone app.
2. Season Proof Your Solar System
It’s no surprise that solar power harvested during the winter months can be drastically smaller than during the summer.
With shorter daylight hours and a lower traveling arc, the sun is just not able to provide as much power to recharge your batteries during the winter.
Though you can mitigate the problem somewhat with tilt mounts, installing a slightly larger solar array system on your campervan can help offset reduced harvesting during the winter.
Which Solar Panels Do We Use?
We installed two Newpowa 180-watt solar panels on our campervan roof. Together, they provide more than enough power to recharge our 300Ah lithium battery bank.
The dimensions of these panels are also a perfect fit on our van’s roof and leave little wasted space around the edges of the roof.
Want to learn more? Check out our post on the best solar panels for camper vans.
Final Thoughts: Calculating How Much Solar You Need Is Just The Beginning
Figuring out how much solar power your campervan needs is an important first step to building your campervan solar system. But it’s just that, the first step.
If you found this article helpful, check out our DIY solar system build series, where we teach you how to construct your own campervan solar system from scratch.
DIY Solar Build Series
And if you have any questions or comments, please let us know in the comments section below.