So you’re at the beginning stages of your solar system build and you might be asking yourself, “How much solar power do I need for my camper van? 100-watts? 300-watts? Or more?”
It’s a question that we’ve all asked ourselves 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!
Calculate The Size Of Your Battery Bank
In order to calculate how much solar power you need for a camper van or RV, you need to already know the size of your battery bank. If you haven’t properly calculated your battery bank size, you won’t be able to determine how much solar you need.
“But why do I need to calculate my battery size first?”
Because Solar Panels Power Batteries, Not Devices
A common misconception is that you determine how much solar power you need by adding up the electrical requirements of all the devices in your camper van.
Critical to understand: It is your house batteries that power your electrical devices. Therefore, your battery bank should be sized to meet your power demands. Solar panels simply recharge your batteries. It may not seem like it, but this is an important difference.
This is why we recommend first checking out our post on how to properly calculate the size of your battery bank. This post will still be here when your ready.
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.
Calculate Solar Array Size From Battery Bank Size
Assuming you properly calculated your battery bank size from Step 1, you can now calculate how much solar power you need based on the battery size AND type of battery chemistry you have.
Good To Know:
Because lithium and lead-acid (AGM) batteries have different depth of discharge (DoD) limitations, your battery type will influence how much solar power you’ll need for your camper van or RV.
How Much Solar Power You Need With 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.
How Much Solar Power You Need With 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.
Solar Wattage Calculation Chart
|Battery Bank Size||Solar Size|
Sizing your camper van or RVs solar array using this calculation should ensure that the power intake from the solar panels will meet your daily energy consumption, whether you’re parked in sunny weather or under the occasional shady place.
Adding More Wattage To A Solar Array
The calculation guidance provided above is merely a guideline to ensure you have the minimum amount of solar watts to properly power all of your electrical devices under most sunny situations (and occasional cloudy days).
But if you’re able to fit a slightly larger solar array system on your camper, 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%.
Inconsistent Solar Harvesting
In the graph above, you can see how inconsistent solar harvesting can be and is greatly dependent on how much direct sunlight your solar panels can get.
Having a larger solar array system allows you to better weather extended periods of time when parked in shaded areas.
For more: Unbound Solar has a short, informative post on the effects of shade on solar panels.
2. Winter 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 larger solar array system on your camper van can help offset reduced harvesting during the winter. If you’re looking to buy, check out our post discussing 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 camper van solar system from scratch.
And if you have any questions or comments, please let us know in the comments section below.