Choosing the right solar panel to fit your needs

Solar panels come in different sizes and types. If this is your first time looking into solar for your van, then your in the right place. If you choose the right type of panel, battery bank and build a environment to match your needs, you will have reliable and long lasting energy source.

7 Types of solar panels

  • Monocrystalline
  • Polycrystalline
  • Thin-Film
  • Amorphous Silicon
  • Biohybrid
  • Cadmium Telluride Solar Cell (CDTe)
  • Concentrated PV Cell (CVP and HCVP)

I will only discuss Monocrystalline and Polycrystalline which are the two most common used in a van.

Monocrystalline Solar Panels (Mono-SI)

Mono panels have a high power output and occupy less space and last the longest. I have one on top of my van from Harbor Freight $149.99. I purchased them because they work best in Washington State weather where the sun is a problem during overcast spring, fall and winter months.

My Mono panels still charges in overcast weather, although not as fast is if there was direct sunlight. Mono panels also are also slightly less affected by high temperatures compared to polycrystalline panels.

Polycrystalline Solar Panels (Poly-SI)

These panels are made by melting raw silicon onto the panels. This process is much faster and cheaper than monocrystalline panels.

This leads to a lower final price but also lower efficiency (around 15%) and shorter lifespan since they are affected by hot temperatures.

Making a choice

The differences between these two types of solar panels are not so significant. Your choice will depend on your specific situation and money.

How many watts do you need?

Solar panels are meant to recharge batteries and not meant to directly run 12 volt devices (unless you find one that has built in USB or other. Although sunless weather can affect the output of your panels, in a idea situation, the size (100, 200 or 300 watt) of the panel(s) determines how quickly your battery bank can be recharged.

I recommend that you concentrate on the battery bank size first. Heres why?

When I decided to convert my van to a camper I never had or used solar. So I spent several months dusting off my electronic skills and researching my options. I decided to start off small.

While visiting Harbor Freight for something else, they were having a Father’s day sidewalk sale (2019) and I saw 100 watt solar panels for $149.99 – I grabbed the last one and when inside and found a solar battery and purchased both. One 35 amp hour batteries from Harbor Freight, and their 100 watt mono solar panels – total cost around $250.00.

With the 2 batteries at 12 volts — doing the math 12 x 35 = 420 watts for camping. Keep in mind I was new to all of this.

I hooked up my 2000 watt inverter and added a bunch of stuff to my van and plugged them in with no regard to how much power I was consuming. BIG MISTAKE!!

Horrible first night

At camp I watched movies, listening to audio books and drank cold juice. I was in paradise. Throughout the day I kept cool by running a couple of fans. Kept my inverter on so that I had power to my laptop, tablet and cellphone. I also had a small refrigerator.

I was awakened at 3 in the morning by a loud alarm buzzing beneath my bed. It was my inverter warning me of low battery levels. I turned off my inverter and disconnected all of my devices and went back to bed.

The next morning I decided to do some calculations to determine what happened.

  • iPad (45 watts)
  • Seagate Wireless Hard drive (9 watt)
  • MacBookAir (65 watts)
  • Fan 1.8 watts (two of them totalling 3.6 watts)
  • Refigerator (45 watts)
  • Samsung Tablet (85 watts)
  • Water pump (1.3 watts)
  • Light (30 watt)

Add them up and I get 253.9 watts against, ideally, 420 watts of battery juice. I said ideally, because the inverter uses power when it converts 12 volt DC to 120 AC to run my lights and recharge my MacBookAir. I needed to subtract 15/20% used by the inverter from the available watts of 420 that my battery provides.

That would leave me with 399 watts to work with. But because my batteries are acid based I should not drain them below 50% which is what happened.

399 minus 253.9 watts is about 145.1 watts left over, in which my inverter was kind enough to let me know I was in the danger zone. Also, my solar control turned off and showed a low battery warning. That ruined my first night out in my solar camper van. I had to wait until morning for sun in order to recharge my batteries – which seemed like forever.


Since May 2019, on that dreadful day, I built my battery bank up slowly. Today I have a total of 2.5 kilowatts of power (6 batteries at 35ahr). More than I’d ever need. I still have my 100 watt panels on my van and they work so well.

I also run some electronics 24/7 with no worries (sun or shade).

Solar Usage Calculator

This is a tool for determining how many hours you can run one or more devices on your 12 volt or 24 volt system. This tool also does calculations for using a inverter.

Video Tutorial

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Upcoming upgrades and feature enhancements

May 15, 2020 – Add the ability to save and reload personal settings. Delayed until August 2020.

Power For Your Van

Getting Ideas:

There are various resources and sites you can visit to get great ideas for building your vans off grid power. Below are sites I used:

  • Facebook groups
  • Pinterest
  • Youtube
  • Google images

When the question about solar comes up in most FB groups there aren’t enough people knowledgeable of the process to help, or those who know how usually explains how in language difficult to understand. So I wrote this article to make it simple.

The story begins with batteries

Say you have two 35Ah (amp hour) batteries.

2 x 35 = 70

That’s 70 total amp hours.

Your batteries are 12 volt batteries. Multiply the amp hours by 12.

12 x 70 = 840

You have a total of 840 watts of available power to power all of your devices.

Then there’s using the batteries

You want charge your iPad. A iPad Air 2014 uses about 45 watts.

To calculate how long you can keep the iPad plugged into your battery, divide 45 from the 840 available watts.

840 / 45 = estimates 19 hours

You can left your iPad plugged into your 12 volt system you will drain your battery.

But that’s a very simple explanation because usually your running more than one device, like a refrigerator, TV, game console, and etc.

Wait there’s more to know

The idea behind off grid power is to plug in and use more than one device. Let’s look at how you calculate that.

  • iPad = 44 watts
  • 12 volt TV 62 watts
  • iPhone 12 watts

44 + 62 + 12 = 118 watts

Now divide 118 (watts used) by the 840 (battery) watts.

840 / 122 = estimates 6 hours

You can run all these devices together for 6 hour before the battery is dead.

Recharging your batteries

Your batteries need a charging source. I will list 4 of them.

solar kit

You can use the following methods to recharge your system batteries.

  • Van alternator
  • Shore power with a battery charger
  • Solar panels
  • Gas generator

Inverters are bad

You can read the article here: