Connecting solar panels in series vs. parallel. What’s the difference? And which solar connection type is best for van life?
We’re glad you asked! This post discusses the differences between connecting solar panels in series or parallel. We’ll also touch on the pros and cons of each type of connection and which connection we ultimately prefer.
- Physical Wiring Differences
- How Series & Parallel Solar Connections Affect Power Output
- Pros & Cons of Series Solar Panel Connections
- Pros & Cons of Parallel Solar Panel Connections
- Which Solar Panel Connection Type Is Best for Camper Vans & RVs?
- Final Thoughts: Series vs. Parallel? Which Is Better for Solar Arrays?
Physical Wiring Differences
Every solar panel has two attached output cables: one POSITIVE cable and one NEGATIVE cable. You can attach multiple solar panels together with these output cables 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 ‘series.’ The other method is to connect your solar panels in ‘parallel.’ Below, we show you what the physical connection difference looks like.
Solar Panels in Series
In a series connection, the NEGATIVE output cable of the first panel is connected to the POSITIVE output cable of the second panel. Then, the NEGATIVE output 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.
Solar Panels in Parallel
* Solar fuses are technically required in this wiring example but are excluded here for simplicity.
In a parallel connection, the POSITIVE output cables from all the solar panels are grouped together and joined using a branch connector. The same is done for all the NEGATIVE output cables.
The two 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.
Interested to learn more about solar fuses? Read our solar fusing guidelines post to learn more.
How Series & Parallel Solar Connections Affect Power Output
To understand the pros and cons of series vs. parallel solar panel wiring, 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 sunny situations, regardless of whether they’re connected in series or parallel.
But the difference between series and parallel connections comes from the makeup of volts and amps, which are the two ingredients that makeup watts.
Remember: Volts x Amps = Watts
How Series Connections Affect Volts & Amps
It’s important to know that when connecting solar panels in series, the volts produced by each panel get added together. But the amps stay the same.
Therefore, if you have two solar panels that can output a maximum of 18.6 volts and 5.86amps, then the solar array has the potential to generate 37.2V but still only 5.86A.
The fancy math: 18.6 volts x 2 panels = 37.2 volts
How Parallel Connections Affect Volts & Amps
In a parallel connection, the amps generated by each panel get added together. But the voltage stays the same.
Therefore, if you have three solar panels that can each output a maximum of 18.8V and 5.86A, then the solar array has the potential to generate only 18 volts but 17.58 amps of current.
The fancy math: 5.86 amps x 3 panels = 17.58 amps
Key Take Away
Remember This Difference
Series connections add VOLTS.
Parallel connections add AMPS.
Pros & Cons of Series Solar Panel Connections
Here, we’ll address each of the pros and cons, especially regarding camper van life and RVs.
1. Thinner wires | Because fewer amps are transmitted in series connections, you can often purchase thinner wires, saving you money. Read our solar panel wire size guide to learn more.
2. Fewer components | Series connections involve fewer components. No branch connectors and no solar in-line fuses are required.
3. Ideal for 24V Systems | Since series connections add volts, 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.
Broken panel shuts down whole array | If, for whatever reason, one of the solar panels malfunctions, the entire solar array will go down. That panel will either need to be replaced, or the functioning panels will need to be rewired to exclude the broken panel.
Lower efficiency during partial shading | Partial shading drastically affects solar harvesting production, no matter if the panels are in series vs. parallel. But panels in series are more inefficient when partially shaded.
Pros & Cons of Parallel Solar Panel Connections
No problem when one panel breaks down | If one of your panels malfunctions, it does not hinder the solar production from your other panels.
More efficient in partial shade | Though partial shading is still detrimental to harvesting solar energy, solar panels wired in parallel are more efficient at producing power than those wired in series.
More components are needed | To wire panels in parallel, you’ll need branch connectors and possibly solar fuses. Read our solar fuse article to learn more if you’ll need them.
Thicker wires, maybe | Since amps are added up in parallel connections, you might need to purchase thicker wires. But this depends on the overall wattage of your solar array. Check out our solar wire sizing guide to learn more.
Which Solar Panel Connection Type Is Best for Camper Vans & RVs?
If you are building a camper van solar system, this is the most important series vs. parallel question for you.
There is no strict rules to follow, but in our opinion, the answer depends on how many solar panels you are using. Here is how we break it down.
One Solar Panel: Since you’re not wiring multiple panels together, there’s no need to choose. Great!
Two panels: Connect them in parallel. Two solar panels in parallel do not need in-line fuses, making it a simple wiring process, and you still get to enjoy the benefits of parallel wiring.
Three or more panels: Wire these panels in series. This will ensure you have a simple wiring setup.
Which Connection Do We Use?
On our camper van, we wired two 180-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 many 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 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 or worry about combining different wire sizes to create our array. Check out our other post about solar fuses to learn more.
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 more panels are 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.
But when it comes to wiring a much smaller solar array on a mobile vehicle, we think the answer becomes less clear.
In the end, the decision is up to each of us. Do you value wiring simplicity? Do you 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.
If you have any questions, please let us know in the comments section below!
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