How Many Solar Panels are Needed to Power a DIY Camper Van Electrical System

DIY Campervan solar

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Solar panels take the energy from the sun and send it down through a charge controller where it will eventually recharge the batteries in your Camper Electrical system.

Quick note before we get started.  This is just one part of a overarching “How to Install a DIY Camper Van Electrical System” series.  If you’ve just stumbled on this article directly without seeing that, there are likely some things we’ve already covered.  If you want to check out that step by step guide, you can do that here: https://www.explorist.life/diy-campervan-solar

Also, we have interactive solar wiring diagrams that are a complete, A to Z solution for teaching you exactly what parts go where, what size wires to use, fuse size recommendations, wire lug sizes, and all kind of other stuff to help save you time and frustration.  You can check that out here: https://www.explorist.life/solarwiringdiagrams/

“How many solar panels do I need to power a camper”?

First off… Stop thinking in ‘number of solar panels’. Solar panels are measured in watts. There are 100, 170, 200, 225, 265, 300, 335, and 360 watt solar panels.

I missed a few, but the point is, there are MANY different sizes of solar panels on the market and 3, 100 watt solar panels will have the same output as a single 300 watt solar panel.

So: The number of solar panels doesn’t matter.

What DOES matter is the total wattage of the entire solar panel array, which is the wattage of the individual solar panel multiplied by the number of solar panels you have.

3 x 100 watt solar panels equals a 300 watt solar array

How Many Watts of Solar Panels are Needed to Power a Camper?

Now that you are thinking in terms of the size of the solar panel array, it’s time to determine how many WATTS of solar panels you need.

You’ve already figured out how many amp hours of batteries you need from your solar power audit. We will be working off of that number. More specifically, we will be working off of the USABLE amp hours of your batteries.

You need your USABLE battery capacity to determine wattage of solar panels.

Your batteries should be sized for your electrical demands. Your solar panels should be sized to recharge your batteries.

*Don’t think about your solar panels running your electrical devices. Your BATTERIES run your devices. Your Solar Panels re-charge your batteries*

How Many Watts of Solar Panels do I need to Recharge my Batteries?

  • 100 Amp Hours of Useable Power from a battery contains roughly 1280 watts of power (100ah x 12.8 volts = 1280 watts of power)
  • The average hours of sunlight per day in the continental US is 6 hours.
  • battery holds about (100ah x 12.8 volts =) 1280 watts of power roughly.
  • To charge
  • 100 Amp Hours (useable) or 1280 watts of battery in 6 hours, you will need 213 watts of solar panels. (213 watts of solar X 6 hours = 1280 watts of stored power)

Key Takeaway: Estimate 200 watts of solar panels per 100 amp hours of useable battery capacity (100Ah Lithium or 200Ah AGM). BUT KNOW THIS: More solar panels are just going to charge your battery faster, or more adequately in low light conditions. If you have 400 watts of solar, you will charge twice as fast. Increasing the number of solar panels will also help compensate on cloudy days.

Key Takeaway #2: If you want more battery capacity than you have roof space for solar panels, that’s fine! You will ALSO be charging from your alternator and you will also have the option to charge as needed from shore power, or a plug-in at, say, a house, campground, or even a generator. This system is all about being versatile.

Spare me the labor and just give me the baby:

 I recommend 200 watts of solar panels per 100 useable amp hours of batteries as a base guideline.

Once you know the total wattage you need, you can divide the total wattage up into the individual solar panels you would like, which will likely be based on roof space available.

Common Battery & Solar Panel Combos

Now that you know how many and what kind of solar panels you need for your DIY Camper Van electrical system, it’s time to learn if you should wire your solar panels in series or parallel (and why we recommend series in 90% of scenarios). Check that out here:
https://www.explorist.life/solar-panels-series-vs-parallel/

Everything that you are learning here is put to use in our FREE Interactive Solar Wiring Diagrams.  If you haven’t yet, check them out as they are a complete solution for a camper van electrical system.  Check them out here: https://www.explorist.life/solarwiringdiagrams/

Remember, this is just one part of a full camper van electrical educational series.  To see all of the individual guides, click here: https://www.explorist.life/diy-campervan-solar

36 thoughts on “How Many Solar Panels are Needed to Power a DIY Camper Van Electrical System”

  1. I agree with the above comments…I have watched you two before, and are very imformative. Thank You. I plan to have 700-900 watts of solar because of Air conditioning, and yes, I found out, it can be done.. It can’t run 24/7 but with short downtime, use a small quite generator, and also it will charge off the engine (alternator)..I do not know the top van surface I will have on top exactly yet, but I need advise as to picking a few 300watt solar tops. versing smaller ones..I am thinking at the moment 2–300 watt on top..with 300watt on side with swing out bar to be horizontal like the roof…Any feedback would be helpful,,and again, you two have been extremely helpful in many aspects of Van life…Thank YOU both so much……
    Bonnie

  2. Under common battery and solar panel combos I dont see a 100 amp lithium and 200 watt solar combo. It looks like you recommend 100 amp and (2) 175 watt panels. The 100/200 combo would be enough, right? This info is awesome!

  3. I want a massive setup with like like 1200 watts and 1200 Ah battery bank. Is that possible on a van? I know that you can charge with the alternator but what about carrying around a little honda generator when you aren’t traveling or an inverter generator, would that help charge up the battery bank also ? And how long would it take to charge them? Thanks

    1. I want a massive setup with like like 1200 watts and 1200 Ah battery bank. Is that possible on a van?

      Yep! 1200-1300 is the most amount of watts I’ve seen on a van. You can go with more, but then you’re going to be getting into sliding/folding solar racks and such; but still completely doable. For batteries: You’ll have to take weight into consideration, but again; it’s still doable. With the proper amount of funds and effort, anything is possible. 🙂

      I know that you can charge with the alternator but what about carrying around a little honda generator when you aren’t traveling or an inverter generator, would that help charge up the battery bank also ?

      Yep! Absolutely!

      And how long would it take to charge them? Thanks

      That depends on how depleted the batteries are, the size of your charger, and the size of your generator.

  4. Your site and videos have been life changing to our process! Thank you for sharing your knowledge! We have 2 100watt Renogy solar panels and plan to purchase one lithium battery from your combo link above. Our question is about the inverter. When looking at inverters from the site, the inverters start at 2000W with a heavy price tag. Is this because its primed for a much larger set up than we are working with and needing? We have a very tight budget, and top recommended inverters like the novopal 1000W Pure Sine Wave Power Inverter are very affordable. We don’t want to buy something cheap, but can’t afford to overpay for something not necessarily needed.

  5. My Super C cabin currently has 4 Lead acid batteries. 960 CCA each. They are the size of what would start a Tractor trailer (it is a tractor trailer chassis as well). They are not deep cycle. If I use the rule of thumb you wrote, that means I have ABOUT 550 AH of power. That seems optimistic to me. I want to upgrade to solar charging and swap over to Lithium Ion batteries. I have to do this in 2 stages for cost. I am going to set 400 AH LI as my end goal. I want to add solar charging first. For Cost, I thought I would start w 3 – 300w panels and purchase a MPPT unit. 3*300A (38.6 VOC 8.6A) 3*38.6 = 115.8 V
    300*3w / 12.6 v = 71 a SO… A 150/70 MPPT is the way to go right?

    1. Awesome! Sounds like a cool project. a 150/70 would indeed work, but as temperatures drop, you MAY have more output from your panels than a basic calculation will tell you. I dropped it into my solar controller calculator you can find on this page and it’s looking like the Victron SmartSolar MPPT 150 | 85 would actually suit your needs better.

  6. Question 2: If I want to replace Lithium Ion batteries in place of existing lead acid (house batteries) , how do I make sure I have appropriate charging from the alternator? Am I going to have to use “smart” Lithium Ion battery only specifically designed to drop in place of lead acid? Does that limit me to certain manufacturers?

    1. Hey Rich! We actually have a blog post that gives some specifics of charging lithium from the alternator. You can find that one here: https://www.explorist.life/how-to-charge-diy-camper-van-batteries-with-vehicle-alternator/

      Regarding manufacturers of batteries, that will depend greatly depending on the battery. With Battle Born Batteries, it’s pretty straightforward, but for a battery without an integrated BMS, it gets more complicated. So, your mileage may vary if you decide to go that direction.

    1. We have some 300 watt panels recommended on our wiring diagrams at explorist.life/solarwiringdiagrams

  7. nate,

    great blog. the best i’ve looked.
    what does “useable amp hours” mean? is this the c20 rating for the battery? how do you come up with needing 200amp hours worth of battery capacity for say, my calculation, using your awesome calculation spreadsheet, of 84 amp hours/day?
    i have two c20 66ah batteries in parallel, two 175w polycrystalline panels in series. i will use my sweet van only in the southwest. do i really need a third battery? there are so many variables that it gets confusing.
    thanks for putting together this website.

  8. So I have 4 x 236 amp hr wet cell deep cycle batteries. I assume I have approx 500 amp hrs at 12 volts approx 250 usable.
    Was thinking of 2 x 300 watt panels maybe 3.
    Thoughts. I will eventually move to lithium.

  9. In your diagrams you show the 15 amp circuit breaker going from solar array to solar controller with a positive and negative lead going into the breaker. one on each side…Is this correct? I just want to make sure. Is this because the solar panels are in series?

  10. Hi, I was wondering why you write not to think of the solar panels running your appliances but the solar panels charging your batteries which run the appliances? It seems like when it’s daylight and you can run your appliances off the grid that would be your best bet. It seems it would also life on batteries and you wouldn’t be cycling them.

    1. I write it like that because I think that’s the best way to convey my message. If you understand it the way you just described it to me, that’s fine, but I don’t like the way you described how this works and I think it would be confusing to those who I’m trying to educate. That’s why I worded it like I did.

  11. Hey! Quick Question! I have a list of things i want in my 2014 Promaster.
    -about 5 led lights with 12v dimmer switch.
    -fan on the roof
    -to be able to plug in 2 laptops and 2 to 3 phones in USB port
    Kitchen:
    -A stove and sink with water pump
    -A mini fridge

    I was thinking of getting 2 100WATT solar panels. I feel like ill need more. also 2 deep cycle battiers….I NEED HELP!

  12. Nate,

    What van is shown in the solar panel top down photo at the top of this page and what rack system did you use. What was the total capacity of that system

  13. This post, your videos and all your content is spot on. I found it very useful and informative.
    quick question,
    I have read online that Monocrystalline solar panels have an efficiency of 15%-20%. I was wondering if combo recommendations are for the stated wattage on the solar panels or the actual wattage needed ie, for 200W you’d need about 750 – 1000W of solar panels ?

    1. That’s very much not true. You can absolutely get 200w out of a 200w solar panel. There are, indeed, ineffeciencies in solar panels, but if a panel says it’s a 200w panel, you can definitely expect 200w (or more if it’s cold) out of a 200w panel during good sun.

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