When installing a camper solar system, one of the first questions we must ourselves is, “How much solar do I need for my camper van? 100 watts? 300 watts? More?” This is a difficult question to answer accurately because everyone’s needs are different. What is the best solar size for one person may not be the best for you.
In truth, your ideal solar power size depends on your power requirements. The more power you intend to use in your camper van, the more solar you will need. The good news is that you don’t have to do any difficult calculations to identify how many watts of solar you need to install.
This post provides an intuitive, step-by-step guide and includes a free spreadsheet calculator to help you identify the following pieces of information:
- Minimum solar wattage size
- Fuse & circuit breaker sizes
- Ideal solar wire sizes
- Solar charge controller size
Let our solar size calculator do all the work for you.
So if you’re ready, let’s dive into it!
Download Battery & Solar Size Calculator
To start calculating your ideal solar wattage, download our free spreadsheet. The document is available in both Google Docs and Microsoft Excel file formats. (The Google Docs version has a better user interface)
When you open the document, you will be met with an interface similar to the image below. Follow the directions in the pink text box and delete the box when you’re ready to begin.
When you’re ready to begin, scroll down to step 2.
List Electrical Devices & Calculate Battery Size
How much solar your camper van needs is dependent on your electrical demands. The more electricity you require each day, the larger the solar wattage you’ll need to replenish your leisure batteries. Therefore, the first step in calculating how much solar your camper van needs is to list out all the electrical devices you intend to have in your vehicle.
In the spreadsheet you downloaded, fill out the green cells in Columns A-D. You will need to enter:
- Name of each device
- Wattage rating for each device
- How many of each device you intend to have
- The number of hours each device will be running for
Sounds confusing? It really isn’t! For a step-by-step tutorial on how to complete Columns A-D, read our leisure battery size calculator post. Once finished, come back to this post to determine the ideal solar array size for your van.
Go To Part 2 In The Spreadsheet
Once you’ve completed all the green cells, the spreadsheet will calculate your ideal battery size depending on whether you are using AGM batteries (cell F20) or Lithium batteries (cell F21). Next, head over to the next tab labeled:
“(Part 2) Solar System Size Calculator”
You will immediately see a pink text box, just like in the image below. Read the instructions and delete the pink info box when you’re ready to begin.
Identify Minimum Recommended Solar Size
If you filled out your electrical device information in the prior tab (Part 1 Battery Size), then the spreadsheet calculator will already recommend you a MINIMUM solar wattage amount. You can find this information in cell A3.
The spreadsheet derives a recommended battery size based on your electrical demands and then recommends a solar wattage size based on the battery size.
- If using lithium batteries: Recommended solar watts is a 1:1 ratio to Ah battery bank.
- If using AGM batteries: Recommended solar watts is a 1:2 ratio of Ah battery bank.
In the example image above, the recommended minimum solar wattage is 206 watts. Depending on the electrical devices you inputted in Part 2 of this post, this number will change for your needs.
Fill In The 5 Green Cells
In Steps 2-5 in the spreadsheet, fill in the 5 GREEN cells. The spreadsheet already has prefilled information in these cells, as an example. Below, we take you through each step of the process to help you fill in this information.
Step 1: Minimum Solar Recommendation
This is the recommended minimum solar watts for your camper van, which is based on the electrical device information you provided in the previous tab.
Step 2: Finalize Your Solar Watts
Based on this minimum wattage recommendation, decide how many watts of solar you will ACTUALLY install on your camper. Ideally, your final solar wattage will be equal to or larger than the minimum recommended wattage. (Tip: Search “Solar Panels For RV” on Amazon to see what panel sizes are available in the market.
If you have the budget and space on your roof, adding even more watts to your van is a good idea to help better offset power production loss during winter and when parked in partial shade.
For more: Unbound Solar has a short, informative post on the effects of shade on solar panels.
Step 3: Decide Quantity Of Solar Panels
Decide the physical number of panels you will install on your camper. For example, if you plan to install a total of 240 watts of solar, you can achieve this by purchasing two 120 watt panels or three 80 watt panels.
Tip: Go for fewer but larger panels, if possible. If you can keep the total number of solar panels to not more than 2, you won’t need solar in-line fuses.
Step 4: Enter Panel Amperage Rating Information
Once you know which exact panels you want, enter one of the panel’s operating current rating “Imp” and its “Maximum Series Fuse Rating”. You can find both numbers on the panel’s online sales page or on the technical sticker underneath the panel.
The image below is Renogy’s 100W solar panel specifications, found on the product’s Amazon page.
Step 5: Series Or Parallel?
If you are installing multiple panels, decide whether you will connect the panels together in series or in parallel. If you don’t know which to do, read this post. If you only plan to have 1 panel, select “Series”.
This is all the information you need to input. The solar calculator spreadsheet will take care of the rest. When you’re ready, scroll down to Step 6.
View Calculator Summary Table
After you’ve completed filling out the 5 GREEN cells, scroll down on the spreadsheet to view the “Calculator Summary” table. From this table, you can see recommended information about your potential solar system in Column E.
This information includes:
- Solar Wattage Size: This is what you entered based on the minimum size recommendation.
- MC4 In-Line Fuse: Determines if your solar system requires an in-line fuse, and which size.
- Branch Connector: Determines whether branch connectors are required, and which size.
- Solar Wire Size: Recommends a minimum solar wire size/thickness.
- DC Solar Breaker Size: Calculates the ideal DC solar breaker size for your system.
- Solar Charge Controller: Determines what size charge controller you will need.
- Circuit Breaker Size: What 12V breaker amperage will you require?
If you are using the Google Docs version of the spreadsheet calculator, each recommended product in Column E is clickable and will take you to the product’s Amazon page for easy purchase.
Download Electrical eBook For Installation Locations
Every solar component in the calculator summary table has a “Part #”, listed in Column D. For example, the solar charge controller is part #16.
To identify where to install each component, download our electrical wiring eBook and locate each product number in the solar wiring diagrams.
Interested In The MOST Efficient (9BB) Solar Panels?
“9BB” solar panels are becoming the next big thing in the solar panel industry. Read our 9BB solar panel post to learn why these panels are more efficient AND have a longer usable life than traditional solar panels.
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.