Solar panels connected in series vs parallel. What’s the difference? And which connection type is best for camper vans?
We’re glad you asked! In this post we will discuss the differences between connecting solar panels in series and parallel. We’ll also touch on the pros and cons for each type of connection and, ultimately, which connection we prefer.
Spoiler Alert: Our connection preference depends on the number of panels in the array.
DIY Solar Build Series
Table of Contents
Series vs Parallel: What’s The Physical Difference?
Every solar panel comes with two attached output cables; one positive (red) cable and one negative (black) cable.
With these output cables, you can attach multiple solar panels together to create an ‘array’.
And there are two DIFFERENT ways to connect all these output cables together.
One way is to connect your solar panels in ‘parallel.’
The other method is to connect your solar panels in ‘series’.
Both ways have their pros and cons. And we’ll get to that. But below we show you what the physical connection difference looks like.
In series connections, the negative output cable of the first panel is connected to the positive output cable of the second panel. Then the negative cable of the second panel is connected to the positive cable of the third panel. And so on, for however many solar panels you have.
Finally, the positive cable of the first panel and the negative cable of the last panel are connected to the solar charge controller.
In parallel connections, the positive output cables from all the solar panels get joined together, using a branch connector. The same is done for all the negative output cables; they get joined together using a similar branch connector.
The branch connectors take all the positive and negative cables and output a single positive and negative line, which then gets connected to the solar charge controller.
How Series & Parallel Connections Affects Volts and Amps
Before we talk about the pros and cons, it’s important to understand how series and parallel connections affect the solar array’s electrical output.
Under similar situations, solar arrays connected in series and parallel will output the same amount of total watts (w). So if you have three 200-watt panels you will output close to 600-watts under ideal situations, regardless of whether they’re connected in series or parallel.
But the difference between series and parallel connections comes from the volts and amps, which are the two ingredients that make up watts.
Remember: Volts x Amps = Watts
It’s important to know that when connecting solar panels in series, the voltages (volts) of each panel get added together. But the current (amps) stays the same.
Therefore, if you have three solar panels that can output a maximum 18 volts and 11amps, then the solar array’s operating voltage has a potential to generate 54 volts but still only 11amps.
In a parallel connection, the current (amps) generated by each panel gets added together. But the voltage stays the same.
Therefore, if you have three solar panels that can output a maximum 18 volts and 11 amps, then the solar array’s operating voltage has a potential to generate only 18 volts but 33 amps of current.
Remember This Difference
Remember this difference; that series connections add VOLTS and parallel connections add AMPS.
Now we’ll discuss the pros and cons of the two different solar array wiring methods.
Pros & Cons Of Series and Parallel Connections
As you might have guessed, there are pros and cons in regards to connecting solar panels in series and parallel.
Since we are a van life blog dealing with camper van living, we want to address each of the pros and cons from the perspective of solar panels being mounted on the roof of vehicles.
(As opposed to being mounted on a large roof of a stationary house.)
Consistent Wire Sizes
You won’t have to worry about what size wire gauge you’ll need for your solar array.
Wire everything together with 10 AWG wire and you’ll be fine.
Better For Longer Wire Runs
Voltage tends to drop across long wire runs. So series connections, which combine voltages, are better if you plan to set up long wire runs (think 25+ feet).
Ideal For 24v Systems
Because series connections add the voltages together, you MUST wire your panels in series if you have 24-volt batteries.
If the solar array cannot produce a voltage that is greater than the battery’s, the battery will not charge.
No Need For Fuses
Because the current among all the panels are NOT added together in series connections, you do not need to worry about fusing your solar panel array.
Poor At Handling Partial Shading
Due to how electricity flows through a solar panel array that is connected in series, if one of the panels experiences partial shading (from trees, buildings, etc), total electricity production drops dramatically.
We’re talking about a significant reduction in efficiency, compared to parallel connections, just because of partial shading.
Broken Panel? Replace It ASAP
If for whatever reason one of the solar panels breaks, the entire solar array will go down.
That panel will either need to be quickly replaced, or the array will need to be rewired to exclude the broken panel.
Greater Productions During Partial Shading
During occasions when a single panel might be partially shaded, the drop in total solar productivity will not be nearly as drastic as if the solar array were wired in series.
This is great if your camper van is parked in a setting with lots of trees or buildings.
Broken Panel? No Production Breakdown
If one of the panels breaks, no sweat. You’ll lose the production from that panel, but your batteries will still be charging during the day from the remaining functioning panels.
Less Ideal For Longer Wire Runs
Solar arrays in parallel carry significantly less voltage than their series connection counterparts. This makes parallel connections less ideal for longer wire runs.
But in a small van, there are likely no long wire runs. So for us, this was a non-issue.
MIGHT Need Fuses
Depending on how many total panels are in the array, choosing to wire in parallel MIGHT require correctly sized fuses to be installed within the solar array wiring system.
To learn more, read “How to properly fuse a camper van solar array”.
MIGHT Require Thicker Wires
Depending on how many total panels are in the array, choosing to wire in parallel MIGHT require thicker electrical wires to carry the sum of the current from all the solar panels.
But this depends on the size of the panels and how many panels are in the array.
Which Solar Array Wiring Method Is Best For Camper Vans?
This is the most important question and likely the one you want to know for your own DIY camper van build.
And the answer is: it depends!
Different people will give you different answers. But if you’re interested in our opinion, here it is.
- Running A 24v System? Wire your panels in series.
- Have only one panel? Cool! You don’t have to choose. Very nice.
- Have two panels? Wire them in parallel.
- Have three or more panels? Wire them in series.
“What’s Your Rationale?”
To understand why we came to this conclusion you will need to understand the basics of fusing guidelines for solar arrays.
We get it, fusing a solar array is really not an interesting topic. But we highly encourage everyone to give our fusing post a read to learn more about camper van electrical safety.
How We Wired Our PV Panels On Our Van
On our camper van, we wired two 175-watt solar panels in parallel.
We did this for two important reasons:
1. Maximize Production During Partial Shading
Living in a camper van, we knew we would be parked in a plethora of different lighting situations.
Sometimes our van roof would experience unlimited direct sunlight.
Other times we’d experience plenty of partial shading from trees.
And since we planned to park in plenty of national parks and boondock on forest lands, combating the effects of partial shading by connecting our panels in parallel was important to us.
2. No Need For To Fuse Our Solar Array
Lastly, because we only intended to install two panels on our roof, we didn’t have to fuse our solar array system and didn’t have to worry about combining different wire sizes to create our array.
Final Thoughts: Series vs. Parallel? Which Is Better For Solar Arrays?
When it comes to installing solar arrays on houses, the answer is more clear. Because there are more panels involved, wiring solar panels together in series provides more upside. You can keep wire thickness sizes to a minimum and you don’t have to worry about those pesky fuses.
House roofs may also experience less partial shading from nearby trees & buildings.
But when it comes to wiring a much smaller solar array on a camper van, we think the answer becomes less clear.
In the end, the decision is up to each of us. Do we value wiring simplicity? Do we value maximizing production in partial shading situations?
We hope that by the time you’ve reached the end of this post, you have a greater idea of what type of wiring is best for your own solar array system.
DIY Solar Build Series