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

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

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:

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:

“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:

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:

Remember, this is just one part of a full camper van electrical educational series.  To see all of the individual guides, click here:

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How Many Batteries are needed in a DIY Camper Van Electrical System

Garry Slyfield

Monday 4th of January 2021

It nice to read an article that cuts to the chase and gets right to facts and knowledge that is being shared to allow the rest of us an easier, trouble free installation the first time around instead of the learn by trial and error that we have experienced at some point in our lives. As they say, " knowledge is power" and for those looking to know more on solar system set ups, this is one article I'd suggest that person read before they start their venture.

Nate Yarbrough

Tuesday 5th of January 2021

Glad it helps. :) :)


Wednesday 18th of November 2020

I already have a 100 W panel and I was wondering if I can mix them and buy another one with the highest amount of watts that I can get (175w) with the same dimensions at the 100 watts I now own. So I would have a 100w, a 175w and another 175w.. Will that work?

Nate Yarbrough

Wednesday 23rd of December 2020

Here is a video that will teach you how to figure out if that setup will work:


Wednesday 11th of November 2020

Hey guys I just jumped into my solar system education rabbit hole today and I am this far into it. I just wanted to say that your links on this page to a 300W solar panel takes you to a 175W panel. I'm unsure if you're recommending to buy two 175W panels to make the 300 or if the links have just changed over time. Thanks for all this great info it is very helpful. I am doing a small system in a 1995 Ford Econoline that I purchased a few weeks ago. My first build! @scarlettjovanson

Nate Yarbrough

Thursday 31st of December 2020

The links have likely just changed over time, depending on which one you are looking at. All of the solar panel links on the wiring diagrams here should be accurate, though:

Tim Perry

Thursday 17th of September 2020

Hey Nate, I am looking at mounting my panels over my two maxxair fans, such as you did. Do you have any information about how you customized your Aluminess rack to make this work? I'm not finding any other solutions.




Monday 14th of September 2020

I've been working through this in order to add solar to my camper/RV. I need 130 Ah of solar, based on your spreadsheet.

The spreadsheet recommends I get 300 Ah of AGM batteries and 400 W of solar.

I was a little confused. ~130 rounded up (to the nearest 50) is 150. Since I'll use AGM batteries, than means I need 300 Ah (since I shouldn't cycle below 50%). This far I follow. But I wasn't sure why it recommends 400 W of solar panels. This ( article made me think I need double the battery capacity. So since I'll deplete the batteries by 150 Ah, wouldn't I need 150 W of panels? I noticed you used different calculations in those cells, one is CEILING and one is ROUNDUP. I wondered if it doesn't work accurately if my input (Amp hours a day) rounds to a 50 and not a 100. Or whether it is intentional? The reason being if I change my power consumptions to add up to say 160 Ah, then it tells me I need 400 Ah of AGM and 400 Watts of solar, which I'd expect.

Any wisdom/corrections greatly appreciated, And thanks again for the great resource,

Nate Yarbrough

Wednesday 16th of September 2020

This spreadsheet rounds your battery bank capacity UP to the nearest 100Ah. So...200Ah in your case.

The solar array is based on Amp Hours of Lithium battery bank capacity * 2 = Solar array wattage; so 400W of solar panels in your case.